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Interview of C. Martin Stickley by Robert W. Seidel on 1984 September 22, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4905
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Laser work at Air Force Cambridge Research Laboratory (AFCRL) (Rudolph Bradbury); early work on ruby lasers (Charles H. Townes, John Howard); Department of Defense (DOD) high-energy laser program; Steve Harris and Anthony DeMaria; optical masers and phased array lasers; CO2 laser at Avco-Everett; reform of service laboratories (Peter Schweitzer), 1960s; laser color centers and pump light attenuation (application to rangefinders); interaction with Office of Naval Research; spinoffs of laser research. Laser damage studies at AFCRL (q-switching); instigated by Peter Avizonis and Art Guenther; Raman light (R. K. Chang), development of Optical Parametric Oscillators; simulated Brillouin scattering (George Wolga); tunable laser work (Tony Siegman, Steve Harris); Avco Gas Dynamic Laser (GDL); Erlan Bliss and Dave Milam; Stickley replaced by Howard Schlossberg; dispersion of laser damage group; transfer of laser glass and damage experience to DOE—Livermore. Stickley moves to Defense Advanced Research Projects Agency (DARPA); Glenn Sherwood, Maurice Sinnot, Ed Gerry, David Mann, Steve Lukasik; Laser Window Program; DARPA interdisciplinary materials science program; Chemical Laser Damage Program (J. A. Harrington). Joins the Department of Energy (DOE) and its laser fusion program; politics and recruitment; Lawrence Livermore Laboratory vs. Los Alamos National Laboratory; DOD vs. DOE laboratories. The Strategic Defense Initiative; Stickley moves to Battelle Memorial Institute.
We are in the office of C. Martin Stickley at the B.D.M. Corporation in Tyson’s Corners, Virginia, to talk about his experience in military laser research and development at the Air Force Cambridge Research Laboratories, the Defense Advanced Research Projects Agency, and later with the Department of Energy Laser Fusion (Inertial Confinement Fusion) Division. Good morning, Dr. Stickley.
I guess your laser career really began when you were a first lieutenant at the Communications Sciences Laboratory at the Air Force Cambridge Research Laboratory in 1960, and in your resume you say that you operated the first laser for the Air Force in December of that year. Can you tell me about that?
Yes. We were in a Communications Sciences Division and the head of that division, who was about some three levels above me, heard about the laser, and said that he wanted one in his laboratory to build one. My boss and I, who at the time was Rudolph Bradbury, both immediately were enthused about doing it. That was probably in the September time frame. Maiman’s work had been published in August, and we set about building one in September and had such device working, I think, in early December or sometime in the Christmas time frame. I’ve always, in looking back on that, have been impressed by being able to move that quickly. I think is unusual to be able to do so those days in those days we could, and we obtained basically Ruby seed rod from another group at AFCRL which was in the crystal growth business; they grew ruby there, and so we started with seed rod, very heavily doped, and in fact it lased, and so it was a very exciting time.
This was sort of in the Material Sciences division of AFCRL?
No, it was the Solid State Sciences Division of AFCRL. There were various people in charge of crystal growth there, from which we got this material.
What did you bring to this project? What was your background at this point?
Well, my background was one of young electrical engineer interested in materials, in optics, but basically interested in materials. We were doing semiconductor device work at the time: avalanche operation of junction transistors and doing circuit work. It was just entirely new.
But you went into it more or less enthusiastically?
Oh yes, enthusiastically and then spent the sixties in a very interesting, exciting decade of laser research.
One of the things you also proposed in this early time frame was operation of the R-2 line of ruby, which was in fact achieved I guess by McLung and Schwartz and Meyers in 1962. Was there any connection between your suggestion and their accomplishment?
I don’t really know, I never followed it up. We often, in our efforts to understand why lasers did what they did in those days, just thought that it should be observed, and so we in fact tried to do it ourselves, and looked carefully spectroscopically but never really saw it. Whether or not there was any connection between our even publishing something in an AFCRL report about it and their doing it, I don’t know.
You knew that Schalow had earlier said that he didn’t think that one would obtain laser action on that line?
I’m not sure we were aware of it. I just don’t think that we were. I think we were puzzling as to why it shouldn’t and thought that that would be something we would look for, but basically, one can argue that because of the spatial energy diffusion processes within these lasers, that that in fact might occur, but those lines are so closely linked in terms of their own relaxation time between electrons, between these levels, that you would have to seriously hold off the R-1 line from operating in order to see the R-2 line, which is what eventually was done. They got some mirrors with enough dispersion to be able to do that.
But this suggestion then largely comes out of spectroscopic considerations.
Yes, spectroscopic considerations and more or less a thought of, “Why shouldn’t it be lasing?” and a thought that we should look for it, to determine whether or not it could be made to lase.
Do you remember whether at this time you were retooling yourself, about lasers, in a way that you hadn’t before?
Oh yes, we were certainly doing that and trying to understand Townes’ and Schalow’s article and chasing down copies of the early quantum electronics meetings which were held maybe every two years through the fifties, trying to understand those articles. While we achieved laser action with these materials, it was of a very erratic nature as to how they worked. Because we had a source of people at AFCRL who could grow ruby, we felt that it would be a direction that we should pursue, and we concentrated mostly on that in the early days.
So the chief influence is that resource in deciding to go in that particular direction?
Yes. The thing that influenced it was that we felt that the proper and best use of lasers would be made if you understood why they worked the way they did, and we noticed especially that the special qualities of the beams from ruby systems were hard to understand. We had sources of Verneuil grown (or Czochralski-grown) ruby at AFCRL which was, to some extent, a different source compared to others; so we felt that some combination the availability of that ruby as a source, versus getting it from Linde, might make an important contribution, and so we focused our efforts in the first years, I guess, in this particular area.
Would you say that the proximity of people like Townes at MIT and Bloembergen at Harvard had any influence on what you were doing?
You didn’t interact with them very much?
There was a little bit of interaction with Townes within the first several years, there was a reorganization of AFCRL and the group in which I was located, was moved out of Communications Sciences. Our group was moved under Optical Physics, and the optical physics people — John Howard, for example, who is now the editor of Applied Optics — were supporting the work of Charles Townes, with Air Force funds, and so there was some connection, but it was pretty remote.
Your own work was spectral analysis of ruby laser light and particularly looking at the time variation of the axial frequencies in ruby light using I guess various things like fiber optics, photomultipliers –-
Streak cameras –-
And that sort of thing. And as you say, you began because you had the rubies available and these questions arose. You reported that this work and some other work that AFCRL did, and here I quote, — “uncovered definitely anomalous behavior with respect to their recent theory on multi-mode oscillation. Ruby lasers failed to oscillate with anything like expected number and distinctness of longitudinally different modes.”  Can you recall that issue at all or comment on it? What theory are you referring to in particular?
Read that statement again.
You report that your work uncovered “definitely anomalous behavior with respect to recent theory on multi-mode oscillations. Ruby lasers failed to oscillate with anything like the expected number and distinctness of longitudinally different modes.” Now, one can understand from that that you get a lot of spiking?
We did a number of things; we were looking at the transverse mode behavior as well as the longitudinal mode behavior, with fiber optic probes and streak cameras. I think what we were talking about there is that the number of modes which appeared to lase simultaneously appeared to be a lot reduced; if you looked at it on a time resolved basis, the number of them appeared to be far less than expected. If you integrate over the whole pulse of the laser, you saw many more modes. And what we were seeing there was, on a time-dependent basis, a few modes at a time. I think that, perhaps, is what I was getting at with respect to that comment.
So you were seeing some sort of a mode selection process?
Does this mean you’re going to get more power out of the thing in some ways?
Well, yes, it certainly did, because one felt that the fact that it changed frequency meant that you were really extracting energy from different spatial regions within this ruby rod, and if you had some way to effectively achieve the spatial averaging in some way within the material, you’d probably have the best chance of getting most of the stored energy out.
Were you interested in high power per se?
No. We were just interested in the dynamics of it and what caused it to do what it did. We were interested in the mode structure. We were most interested in the transverse mode structure, because earlier work by a bunch of people — it was easy to resolve longitudinal modes — and so we did that routinely. We looked more at the transverse modes, the transverse modes that controlled the focus ability and the beam divergence, and so we focused much more on that.
Well, of course, in 1961, ‘62, Wright Patterson was doing a fair amount of fairly ambitious and perhaps not too well-conceived laser work, including big high powered testing facilities that they were trying to build, and Project Seaside was being launched by the Office of Naval Research, and one of the things that Seaside did was to survey what was going on in the services. Did you have any connection with this activity? Did it have any influence on your work?
I had little if any connection with that activity. The earliest I remember getting into such things was probably more in 1965. Our group was doing sufficiently basic work that it really wasn’t connected in very well in that way. We had a project there in the Air Force R and D structure. There was a project at AFCRL which I became the manager of, which was funded by monies from Wright field, but again these dollars were small laser technology and development dollars that they were connected with a project of that sort.
More 6.1, I guess.
6.1, I guess, but any Wright Field money was 6.2 money. But we funded some of the earliest work with Steve Harris at Stanford, and, it led to, for example a little company called Chromatics, that built the first optical parametric oscillator.
This was a little later down the line.
Yes, this was a little later down the line. But it was money for basic technology, really understanding. We funded much of the early work of Tony DeMaria, United Aircraft, and Tang, Stetz and DeMars of Raytheon.
You were a member of the Special Group on Optical Masers?
Yes, I was the AFCRL representative on that.
OK. Were you there at first or were you there after it had been going?
When was “the first”?
Well, I think it was set up as an ad hoc group on optical Masers around ‘61, ‘62, and later became the Special Group on Optical Masers around ‘63, ‘64.
Yes, I probably got into it more in ‘63, ‘64. I certainly wasn’t in ‘61.
Did this give you sort of an overview of lasers?
Yes. It was a very valuable experience because on a regular basis, it got various DOD people together: Bill Condell, Rudy Buser, myself, Bob Kingston, at the time at Lincoln, Bob Collins, Peter Franken, John Walsh, IDA people. It was a very stimulating experience because it was sufficiently free from politics and competitiveness that the meetings were characterized by times for discussion and clarification of the issues, of what people were driving at. It was a very valuable experience.
Can you recall whether when you first joined this group there was any perception of the DOD laser program as a whole? You came from one part of it, but here was a chance to see what was going on in some other areas.
No, because the group was, at the earliest times, for example the high energy laser program, whose activities were not coordinated through the AGED, and so we as a group weren’t really connected with that.
But you were for example looking at things like range finder development? Do you have any recollections about that or the state of the art?
Nothing very strong, except that it certainly, looking back at it, it certainly has been a slow evolution of the technology, because certainly the ideas and the concepts seemed to be right there in the early of mid-sixties, and frankly it doesn’t seem like, in 20 years, there’s been much in the way of substantive changes. The issues then were how to do Q-switching, rotating prisms were tried, and Keir cells. Range finders at that time were very simple. It was sort of an engineering issue as to how you in fact most effectively accomplished these kinds of functions.
Do you have any recollection of the Frankford Arsenal work on Q-switching? They have a claim to being among the first to use rotating prism type switches.
Yes, I have some early recollections of work going on by the Army. I guess Frankford Arsenal. I’m not sure because that’s fuzzy, but it was led probably by that group, and some of the early rotating prism work, a guy named Mike Mirarchi; I remember him as being a key person from that group. But I wasn’t really focusing on that. I can remember that sort of in a fuzzy way during that time.
In general it was fairly diffuse program and at the level of systems rather than the level of basics.
Yes, it was a program — for example, taking a lot of the Wright Field type activities — it was a program of early attempts to use lasers often in ways for which they weren’t suited. Lasers themselves were in a hot state of evolution. New ones were being found. New directions were always being sought, new crystals, new gasses, yet built into all of that was a mix of efforts to put them to early use. For example, I can remember many discussions about phased arrays, in those days, and I can remember the Special Group on Optical Masers trying to put that to rest on numerous occasions, but Wright Field would continue to come back with an interest in phased arrays, even though it seemed like the technology wasn’t ready at all for being able to do that. They just didn’t have the phase control.
So in these meetings you stated your point of view to these other people.
Well, yes in these meetings, I described how we wanted to spend the money that we had, and generally, the politics was such that you generally weren’t critical of what the other laboratories within your own service wanted to do; but on a technical basis, you certainly participated around the table in discussions and had no limitations. So it was an attempt to organize, in a very small and indirect way, the plans and programs of these different DOD funding agencies and laboratories. It was only effective, I think, for the people who were there and participated, and to the degree that they could go back to their home organizations and influence what was done, I think that’s about the only influence it had. But for those who were there, it was an important part of our experience.
Of course as you say it was a hot period in the development of lasers. Do you recall any particular technological opportunities that opened up in this period that in any way galvanized this committee? For example, did the use of neodymium: YAG as laser material strike them as a breakthrough, or was it just one of many developments?
No, it was one of many developments. Joe Geusick’s work at Bell was, I guess, the first to show it. It was just one of many things that were being pursued in those days: all sorts of materials, devices, coherence, studies of the coherence, lots of thought of liquid lasers. In those days liquids were pursued, in fact, a lot by ONR, and that turned out to be a real loser in the long run, certainly not a winner. But the committee tried, on an annual basis, to try to define the state of the art at the time, what the problems were, what directions the technology thrust and off shoots should go. For example, higher power operation of the YAG systems was always something that was sought in those days, multi-watt, up to 100 watts. But there was no understanding. The whole evolution of nonlinear materials for doubling was coming about. The problems of inducing undesired refractive index changes in those materials, and basically screwing up the doubling process, was something that people were coping with, but didn’t know how. So that was a large part of it. But there were a myriad of things that were driving what was going on. I wouldn’t say that there was anything, any particular focus to it. Basically, SGOM did not have the power to force the development of a coherent, DOD 6.1 and 6.2 program.
Nothing that stands out, at least from this point in time. You worked with Lipke at NASA, and T.J. Healey at STL,  on mode and polarization phenomena of ruby lasers. I’m interested in how that particular connection came about. I gather that Healey provided the streak camera that you used.
Well, Lipke was at AFCRL at the time the work was done. He later moved to NASA, Healey had a camera and we used it for work looking at time-dependent polarization phenomena.
And also some beat frequency detection as well?
I guess the streak camera is rather unusual. This is a facility which was not common.
The beat frequency business, though, was quite common?
Well, it wasn’t in the frequency range we were looking at. We were the first ones to really find beats which would occur in the 30 megahertz range, and in fact that constituted much of the thesis work that I did, the understanding of that.  So that was very uncommon, and in fact the camera was one way of recording that, and in fact I guess it was one way of seeing that, because you could see typically, 10 to 50 megahertz spatial oscillation of intensity across the face of the beam, and we later set up photomultipliers with filters for frequencies of 10 to 50 megahertz to look for that. So the early work I did was really to understand what they were, and it turns out that they were in fact different frequencies between transverse modes having the same longitudinal mode number, and that observation was the basis of my thesis work.
In your work on transverse mode beats in ruby, you report that Sturge and McCumber had explained the phonon processes which caused homogenous broadening of the R-lines in ruby, and this led you to explain these transverse and axial mode beats as beats between the transverse modes, as I guess you had indicated. In your thesis then you went back in 3-D resonator theory, and used the experiments you were making with the ruby rods of varying qualities to show that this could be predicted from the resonator theory, hut the beat frequency spectra from poor quality rods could not be described in that manner. Would you tell me a little about that?
Yes. Because of our source of ruby, we were very fortunate to get some excellent optical quality Czochralski-grown ruby, and that formed the basis for most of the observations which led us to learn something. Poor quality ruby, in an optical sense, had such optical distortions which would not allow coherent modes as we knew them to develop. And in fact, if you looked at the spatial emission pattern of a poor optical quality ruby, it consisted of fairly uncorrelated emissions over the surface, with various time dependencies, whereas an excellent quality optical ruby would behave like most lasers that are known today. That is, there’s a spatial coherence across their face. One has an optical media which is good enough, which can support a single spatial mode. Poor ones didn’t. And so, when they didn’t, there was no simple way to describe what their mode structure would be. And occasionally, one could see a very high order Hermite-Gaussian mode from some part of a ruby rod, but that would appear, and then, other emissions would occur from other parts of the ruby, and they wouldn’t be particularly correlated. It was just a bunch of garbage coming out, by and large. So we learned this from measuring the modal performance of good optical quality ruby; we could measure the modal separations in these beams. We traced them back and determined that they were characteristic of a resonator with a certain curvature, and found out that that curvature was more than you’d expect from just looking at the ruby passively in an interferometer. I later chased that down to determine that it occurred during the course of the laser being pumped, that there was a thermal distortion which was induced in this rod, and then that led to other things. 
Yes, I think of course that’s the work that Townsend and you did — the thermal distortion work?
And this is flowing, as you say, out of these studies of materials, and the electromagnetic properties of the rubies you were working within the laser system, not flowing out of any particular military mission at this point?
Now, while you were doing that work, you also had a contract with Milne and Hercher. What was the relation between their work and yours?
Yes, Mike Hercher was an outstanding fellow under Gordon Milne and Caroll Alley. Caroll Alley is now at the University of Maryland. And Mike did a magnificent PhD thesis there in the early sixties, about all sorts of aspects of the ruby laser, and my office, through the project funds we had, supported the work that was on there by him. He looked at a great number of the dynamics of the ruby laser. He characterized the relations between the spiking characteristics of ruby and damping rates as he could predict them, things of that sort. And so we supported his work. Our own work went beyond that and we looked basically at the transverse mode structure.
You went beyond diagnosing these problems into trying to compensate for them, and you do this by working out a means of compensating for the pump light non-uniformity and the thermal effects, by using a sort of external mirror.  Now of course when I read this it immediately suggests an early form of adoptive optics — I’m sure that word wasn’t being used at that time — and I guess this comes out of the fact that we’re looking at the Seigman studies on resonator theory and can you tell me how you developed this technique and was it unique, was it unusual?
Well, other people were looking at the thermal distortion of ruby rods. There was a German fellow who was in Port Monmouth who was doing some similar work. But we traced down what this curvature was, and it just seemed like a natural thing, knowing what the focal length, if you like, of that rod was, to, in fact, design a cavity (by that I mean a mirror) which would compensate for that. Thus the idea was just kind of obvious, that it was something that would be very important to do, if you could balance out the effect of these thermal distortions. So I measured what this focal length was, and then had a mirror made, which I thought would on average compensate for this, and put the mirror in, and, low and behold, this all worked very nicely.
Did it work for a long time?
Yeah, it worked. In fact it was unusual. It worked over the whole time of oscillation of the laser, which was hundreds of microseconds. It seemed it had an effect over that whole period of time. And basically the theory that we used at the time was really the Jim Gordon’s theory and Kogelnick and Gordon, I guess, but Tony Seigman’s work was a bit beyond that. He was looking at unstable resonators, and while the thought was, the diffraction losses of those might be too large, what I was really trying to achieve was pretty much just on the border of getting into unstable resonators, where you had a flat-flat equivalent system. So it worked, but of course it really only made sense in good quality ruby. Doing that for lesser quality ruby didn’t make much sense for the reasons I’ve given earlier. If you had a very poor medium it didn’t matter what the mirrors were outside. It wasn’t going to change things very much.
What sort of community did you see yourself as working in? I’m thinking not of APCRL but, who were the people with whom you were regularly corresponding, at Hughes, at NRL?
Basically the Hughes guys; Victor Evtuhov was one. There were people at Pt. Monmouth whose names I’ve forgotten. Bob Collins who at the time I guess — no, he basically — I guess I didn’t meet him then. In those early days, the discussions were mostly with Hughes group, and comparing notes as well with people in the Army; also with Mike Hercher at the University of Rochester.
Not Bell Labs?
No. Not Bell Labs. They did little in ruby lasers. Collins had published their work on these quickly and they left there. He was at IDA at the time, around ‘62 to ‘63. A lot of the later work, we discussed with colleagues including Collins, who went to Minnesota, and set up a group, and that kind of grew out of our associations and connections with the Special Group on Optical Masers.
So basically it is a military lab contractor community that you’re talking with.
And you’re publishing of course in open literature?
Yes. It was a research laboratory. In those days, we just saw the ultimate utility for any application, be it range finders or whatever, depending on the basic processes in these lasers, so it was a great puzzle. We got into other work later on which stemmed from chasing observations that nobody understood, so that was the basis for a lot of it. At AFCRL, I can remember defending what we were doing relative to applications and we successfully did that, but we had to explain that there were aspects of the operations of these which could be dominant in how you used them, and some work needed to be done on unraveling some of the peculiar things that these lasers did. I think we did fairly well at that.
Did any of this work seem to be ultimately applicable to high energy laser development?
Well, how are you meaning high energy laser development?
Well, for example, one of the common problems is getting a diffraction limited bead with a ruby or glass laser, and some of your work on optical oscillators is related to work that was done using Raman scattering to more or less clean up your beam quality. You pump a Raman cell with ruby a laser and you get a neater beam out of it.
You get higher efficiency; you may get high enough power to be interesting. In other words, if you can get a single mode out of a ruby laser itself, obviously this is of great interest for beam quality if not or power.
We did it just strictly because we knew that that would be important. At the time we didn’t know all the intricacies of how you make Raman cell better. That came much later. It just seemed like in any effort to focus the beam, you just simply wanted as clean a beam with as little of this funny structure in it as possible, I was motivated by strictly the knowledge or the bet that that was going to be important.
So it’s what you might call a variety of fundamental research.
Only it’s justified in terms of possible applications.
But the applications are nothing that are terribly clearly defined.
In other words, we can apply lasers if we understand lasers.
That’s right. It was that sort of argument, and its application to high energy lasers, you know, the first that came along that seemed to make any sense was the CO2 laser at AVCO, and that seemed to be a different kind of thing entirely. That was in ‘66 or ‘67. And the work you and I have been talking about was done some years before that.
Certainly later on when Schlossberg came to AFCRL, there was still this atmosphere of fundamental research, in other words, with some applications loosely in mind, which was prominent.
But you’re familiar with what’s going on at NRL, the Air Force Weapons Laboratory, and Wright Patterson. But it seems to me that those activities are more closely tied to applications.
These people do have a specific application in mind. What sort of feeling did you or do you have about that kind of thing? Did you feel that AFCRL was a better place to work, a more interesting place to work? Was there any kind of definable difference between that and the other labs?
I guess at the time we felt that our work would be more generally useful and would be a better investment, because we were, we felt, supporting the kind of technology which would have the potential for a number of applications. We weren’t sure at the time that the applications that some people were pursuing were necessarily the best ones, or even worth doing, so, we didn’t especially at the time care all that much. Let me back up to say, however, I’d been working with Art Guenther and Pete Avizouis through all the early sixties, and their problems early on became ones that we focused on. Being a research component of the Air Force we wanted to work on things that they were trying to use in some important way. They were limited by the performance of these systems, and so, I can remember getting very early into the laser-induced damage of materials, driven from that point of view, and so while Wright Field and Air Force Weapons Lab pursued the applications, we pursued the fundamental limitations and worked on the problems that they saw which came up, and this whole business of laser-induced damage to materials — the first work I remember — that gets into another subject.
That’s something we will talk about later on, but one thing I do want to talk about in this connection is the institutionalization of the laser physics program, in the creation of the branch which you headed. At that point you made your transition from being military to civilian, or somewhere along there.
Yes, in 1962.
And the Laser Physics Branch was created and you were the head of it. Now in theory when something like this is done, there is a sort of justification made for it. For example, if one looks at the Naval Research Laboratory, there is no laser physics branch at the Naval Research Laboratory. There’s a bunch of scattered activity in an old fashioned Optical Sciences Branch and solid state work.
You mean that’s your description of it 20 years ago?
In the time period that we’re talking about, the early sixties. You created what you called a laser physics branch. How do you do that? How do you justify it? Why did the Air Force buy doing this? Was it easy to do this kind of thing?
In the early sixties, yes, it was easy to do that sort of thing. But I was young enough at the time that I wasn’t necessarily the one who fought whatever bureaucratic battles were fought. The first chief of that was not me, it was a fellow named Peter Schweitzer. And I took over that from him in about 1965 or so. But that branch had been formulated when, at AFCRL, when it was in communications sciences. It was formulated and called Laser Physics because AFCRL was a research organization, and we felt that was what the real issues were which had to be answered first. So the justification, while as I say, I didn’t struggle with that, it seemed that nobody questioned it. The competence of the people we had seemed to be good. They were productive. The Air Force seemed to be pleased with what we were doing and the whole tenor of the times and attitudes were that it really wasn’t a problem. Lasers were exciting new things, and it was important to them to have a group doing something important in the area.
You may know that at that period of time, there were a number of attempts at what we would now call the Systems Command level to reform the in-house laboratories, not only in the Air Force but in other DOD branches. Now, I don’t know to what extent at that time you were aware of that, but it has occurred to me that probably this is why that period is usually singled out by people like yourself or Harold Bennett or Avizouis as a period when things were particularly flexible and when research was encouraged, the implication being that things have changed and not for the better in the interim period. I gather you would agree with that. I just wondered if you had any perspective at that time on these upper level, higher level interests in building strong in-house research capabilities?
No, I certainly agree with what you’ve said. I mean, it was the post-Sputnik era. In government laboratories, it was before the dominance of accounting procedures came about. The fact that we could build the laser in two months would be unheard of these days, given a typical DOD laboratory, even an Air Force laboratory, and wanting to get into something totally new, and accomplish something in two months. There just isn’t the flexibility in the procurement policies, and that sort of management insight I think just doesn’t exist anymore. In terms of what was going on at senior levels, much higher levels in the research structure of the Air Force, I can recall various organizational shifts, name changes at the AFSC level of what the research component of the Air Force was called, but it had little effect upon the flexibility that we had at the time to do what we all thought was important.
Was that true in general throughout the period you were at Cambridge?
Yes. This continued throughout that period, I left in 1971, and through and into the late sixties, leading up to that time, it was still a very good atmosphere and easy to make changes and to do new things although, I’m trying to recall when things started tightening up. I guess it was kind of a gradual process.
Bureaucracy works in that way, I think.
OK, to get back to the scientific work you did this fairly ambitious study of color centers I guess about 1965.
It was fairly systematic presentation of the research which examined eight possible causes of the degradation of the energy output of the laser, eliminating all that bulk and surface absorption by impurities, which is of course as we know from the laser damage field a fairly important sort of observation, I don’t know how unique, but certainly a key.
But they were different. They were much different.
Well, the color center effect that we saw was a pump light attenuation process, which simply reduced the pump intensity and caused the laser energy to fall off, and pump intensity converted electrons from one level to another and caused impurities, such as titanium which was in these crystals, to move to a valence state where they could absorb pump light, and so, while impurities have different effects, this effect of degradation in the performance of ruby, was of a different sort than that which led to breakdown of materials.
I mean the importance of impurities — as opposed to the competing mechanisms which were suggested, things like electron trapping in metastable states. The work that you allude to does not consider impurities to be a very serious problem. The state of the theory at that point was trying to explain it in terms of intrinsic characteristics of ruby.
Now, can you tell me what suggested to you to look at impurities? Was it because of the material science work that was there?
Well, yes, it certainly had bearing on that, and also, we could just see with your eyeball that the coloration of ruby became different, and we then, with spectroscopic techniques, tried to determine what this was we could see with our eyes that these crystals became more of an orange. We then chased that spectroscopically, and we used the materials science capability or materials characterization capability of AFCRL at the time to help us do that. When we realized that it was something in the material in that way - - you couldn’t very easily put a ruby rod in a spectrometer and make these kinds of measurements — we had to go to some configurations of cuts which we could in fact expose and measure in a spectrophotometer. But it turned out that the most successful way of seeing this seemed to be just with the rods themselves. We were concerned that handling procedures might in fact, influence it. We were very careful to keep them clean and in fact, you could cause this by getting the wrong surface impurities just from your own handling process. But we clearly found that some rods did this more than others, and this just suggested impurity effects within the material, rather than something intrinsic to it.
I wondered whether your experience with semiconductor materials, which had to be manufactured in a highly pure state, suggested impurities as a possible cause.
Well, the other thing that suggested it was the materials characterization capability which existed at AFCRL. They could basically take a sample of the ruby crystal and characterize it in various ways, and break it down into the constituents that were there, and we were always amazed at all the junk that was in a piece of ruby which would lase and always wondered, what in the world does it do, what are the effects? And basically, you could find a great amount of that kind of extraneous material in ruby. It just seemed like this was one of the ways that it might in fact be causing a problem. Of course you could later track it to potential damage sites, if you had occlusions, large clumping of foreign matter in these crystals. One could get damage there. But that’s just another mode of how impurities in these crystals got there.
So everybody knew the impurities were there, it was just a matter that nobody particularly worried about them before?
Well, you know, it was in the days of trying to figure out what was important. You could grow ruby, Linde grew ruby of various sorts. ONR supported this excellent program to grow it by the Czochralski technique rather than Vernueil technique. That gave another insight into what was important in ruby. But again, from a materials point of view, we knew that these impurities were there, and had no idea what they led to or what they caused. And it was just one of the things that’s always in the back of a research person’s mind — you look for correlations, and this is one of correlations that we found.
One of the things that you do in this paper to support your hypothesis is a numerical analysis of the absorbed pump light from the flash lamp, as a function of the radius and the doping and the concentration and the diameter.
It was numerical analysis. We probably felt that it justified no more than just the best rather simple estimates that we could make, as to whether or not this was a sufficient reason.
So there wasn’t any sophisticated computer analysis.
No. There wasn’t.
In this work you use a lot of Linde rods and you used one AFCRL rod, at least in the published work, that’s how it comes across, so in a sense it suggests that you tried a quality control project there. Is that true?
No, it was again attempting to learn by looking at what we thought to be greatly different varieties of materials, and a comparison of their performance, to see what clues there might be as to how they behaved differently.
But they were all Linde rods.
But they were all in many cases different Linde rods, you know. We were in no position to exert quality control efforts on Linde, but we all knew that one piece of ruby was not the same as the other, just judging by its optical characteristics if none other and its impurity content.
I wondered why Linde rods and not AFCRL rods, since you had the capability to produce them there -–
But it was far easier even then to turn money into buying things from a supplier, than it was to reorganize somebody else’s priorities within your laboratory, when you couldn’t pay them to do that, to produce what you wanted. So it was I think it was more a manifestation of that.
So Linde was the best maker of ruby at the time.
Yes, and besides our group was not a part of the Materials Group at AFCRL. We were in a different part of the laboratory, different part of the structure. We were an Optical Physics laboratory which was different. So, we tried to work across the political boundaries at AFCRL on this, and that worked pretty well, but they weren’t really tooled up for producing ten different crystals, Vernueil grown ruby rods, for us. I mean, it was just not what they were set up to do.
Every once in a while you wrote up an R & D summary when you describe this particular project, you had two objectives. One was remedying the unpredictable operation of airborne range finders and target designators, by devising proper passive techniques to evaluate laser rods, thereby eliminating active testing of the laser system. Now, I’m aware that when one writes a work unit information summary one does not always report one’s true motives, but to what extent was this objective something that you were pursuing at the time?
They weren’t reading this work and saying, “Gee, we ought to get this kind of Linde rod rather than another?”
That’s right except I’m sure they were experiencing the effects or lack of, you could say, quality control, or lack of even Linde knowing what was important, in its growth and characterization of the rods.
But in this sense you were hoping more to influence Linde to grow better rods, rather than working for the Air Force to select or evaluate rods.
— yes, yes —
In other words, you’re not developing quality control as this might suggest.
No. I think Linde was very interested in what we were doing because it was indirectly going to help them or even directly help them understand better what was important about rubies, so they could grow better material.
Now, in addition to this, you also say that increasingly subtle instrumentation was developed to measure such things as small angle scattering indexing homogeneities, and to correlate them with output power. The instruments used in the color center study were largely off the shelf, although you developed, what you called a, I guess a magnesium oxide packed powder reflector for that work. Is this writing about instrumentation of the same character, in other words, incidental to the research rather than being the purpose of the research?
Well, it was incidental. It was the kind of thing we had to have to try to understand what was going on. So we would develop, you know, special diagnostics to try to understand what these materials were doing.
OK, we talked a little bit about the Solid State Sciences Laboratory, the reasons why you weren’t able to necessarily get all the ruby rods out of that you could. But one of the things that they developed, there are a number of things that they developed for growing ruby crystals in this period. There was the flame fusion Vernueil technique, but apparently they were important in getting, in trying to improve the Czochralski techniques of growing crystals. They developed a trombone technique for growing ruby sapphire crystals, supposed to provide for greater laser efficiency. Were you involved in any of this work? Was it important to you?
I guess. We were aware of it, but it was not important to us. The Solid State Sciences Laboratory at AFCRL was looking at and embraced techniques which would be generally useful in growing high temperature oxide materials.
You were talking about the Solid State Sciences work.
Yes, the community that they dealt with was the crystal growth community, and their techniques were ones which were useful in a broad way for growing high temperature oxides. Again, we were more or less evaluators of some of these materials, and we would make rods from the boules which they grew. And so we were a component, if you like, of their ways of assessing the different qualities of the crystals which were grown.
Were they particularly aiming at making good ruby crystals? Was that one of their goals?
Well, sure. That was one of their goals. But they often had a grand scheme for doing it which they, in a management way, never seemed to pull off very well. I don’t think it was a tightly enough run laboratory at that time to make much headway there. It was a difficult problem. Let me say that understanding the pluses and minuses of ruby and what made a good one was a very large problem, and while I think they contributed and worked on that problem, understanding it required lots of work in the early sixties by people far beyond their laboratory and ours. The trombone shape was developed for ease of CW laser pumping by Don Nelson and his group, but I don’t recall AFCRL doing much like that.
Well, I gather that the problem there was for mounting ruby rods in certain kinds of lasers, you need sapphire mounts.
Yes, you want to avoid the pump light absorption.
Right: so it’s a way of growing two crystals together, in such a way that the interface is not problematic.
But beyond that I really don’t know. I have not run into the parts of their own discussions in their own AFCRL historical reports.
Yes, you’re right. Your comment reminded me of it. I think they did do that. But it was such a tour-de-force to make such a thing work that it wasn’t a technique which was used especially.
Did anything come out of their work that was ultimately of great value to the services — in terms of crystal growth techniques? Or is this again a kind of a 6.1 program that’s effects are diffuse and hard to follow?
I’d say it was a 6.1 program which, whose results were probably harder to track than most. It fed into the crystal growth community, which in those days was growing with really a strong interest in laser materials, and it was part of what we would call a technology base.
There’s no process we could stick on them and say, without AFCRL we would have been retarded in developing “X” flame fusion techniques?
I don’t think so.
Getting back to laser physics branch, you had a number of research programs of course besides you own. What was Picard and Schweitzer’s work in mode locked lasers?
I think it began with some of the earliest observations at United Aircraft with glass lasers.
This was work you were sponsoring.
This was work that we were probably a co-sponsor of, I’m sure ONR was putting money into it and we were also. This was too in the early sixties, like ‘64. I can remember DeMaria doing his thesis work, and he and I were doing our PhD thesis work at about the same time. I remember visiting and talking about it. Peter’s and Dick’s interests were really very fundamental, the very basic quantum mechanics of it. We supported work of Leonard Mandel and others in the quantum optics community as well as Emil Wolf, for example, at Rochester. And their efforts were more, again, directed at, what’s the basis that this happens? How does it work coherently within these materials and lasers in general? We pursued a very fundamental physics approach to trying to understand what a laser was. It was, you know, Mandel and Wolf who had done some early work about coherence theory, and obviously the laser was a boon to that community, because it gave them a bright source of coherent radiation. Peter and Dick interfaced a lot in discussions with people at Brandeis University, which was also a major 6.1 contractor of ours.
Who was then at Brandeis?
Their names don’t come to mind at the moment. But they were a local group. I think they have gradually moved to Worcester Polytechnic Institute. But I don’t remember their names.
Well, we can add it. [Ed. Note: F. Lipworth]
I would guess Peter’s and Dick’s contributions were more in providing an interface and motivation, and they worked broadly in a discussion mode with Rochester people, Brandeis people, all about some of the most fundamental issues within the laser community. Fred Hopf, for example came to AFCRL from Yale University, also, Marlan Scully, Willis Lamb’s student from Yale, was at MIT for a period of time. They were all part of this group trying to understand lasers from a very fundamental viewpoint. Fred Hopf joined us, looking at short pulse phenomena in addition to coherence theory at Brandeis and Rochester. It was a small community, and in many ways we were at the center of that, supporting research here and there in these areas and in an applied way, with De Maria. You know, we puzzled about the meaning of having a reflection from a surface where you can infer that the surface roughness is in the angstrom range. We just tossed that out as an example of something that no one seemed to understand, yet it seemed to be manifest in the way these lasers were working. So it was an effort to unravel some of the most basic stuff.
How did this stimulate you to interact, how did its members interact? You made personal visits to the labs?
Oh, telephones, meetings, seminars. There were of course quantum electronics meetings, special meetings of various sorts. It was nothing especially organized.
So it was part of the regular scientific community.
Yes, the standard mode of interaction within the scientific community.
So your funding did not imply anything beyond their sending you an occasional quarterly report as far as getting consulting out of them?
That’s right. In those days, let’s say you could only distinguish our source of funding in that we probably knew more about the details of what they had done and were trying to do than somebody at ONR or AFOSR who probably had more responsibilities over a broader spectrum of things to support, and therefore perforce probably knew less about the specifics.
How large funding was this?
Oh, those were the days when a man-year cost 30K. So it was probably no more than a few hundred, or $150,000 a year.
You had about seven, ten projects a year?
No more, that’s larger that it really was. It was a 6.1 project with probably on the order of maybe $150,000 a year. So it supported some professors’ time and graduate students’ time, people for the summer, things of that sort.
Can you specify anything that critically came out of this that you would take pride in having funded, accomplishments? Or did all these people have research programs going before you got in on the thing? Most of them must have had.
Honestly I guess I can’t say that anything strikes me of being of great importance. I think the fact that we supported the ultra short pulse work at United Aircraft and later work at Stanford. These programs were the most visible and have had the longest impact. We pursued the very early beginnings of understanding what’s important in making those kinds of lasers work, and important in a sense of, if you redesign the resonator, what effect does that have? We were chasing things of that sort. Under Tony was a fellow named Bill Glenn. Bill Glenn and a few other guys were in many systematic ways seeing what influence re-designing the Q switch had which was used in those days. The mirror was made an integral part of the dye cell, thus the absorbing dye was right up against the mirror surface; we were trying things of that sort to determine what influence such designs changes had. We were trying to get at what the fundamental things were which would explain some of the peculiar ways these lasers behaved. That style of support probably was more important at United Aircraft for the results it produced that any other thing that we supported.
Now, to what extent did you interact with Fred Quelle and the ONR people? They were supporting research and Fred Quelle was very active, particularly in glass and solid state laser work.
Yes. I saw Fred at the Special Group on Optical Maser meetings. They were supporting a lot of work at American Optical on glass technology. I kept abreast of it in a general way, but there wasn’t much of a direct connection with what we were doing.
You didn’t have regular meetings with them or anything?
What about with MICOM? MICOM was also giving DeMaria some support in this period, and they have some claim to have taught him something about glass laser systems, because they were developing some pretty good glass laser systems there. Did you have any contact with the work at MICOM at this point?
No, we didn’t really. I would say almost nothing beyond that. I think, except for the range finder work, I’d be skeptical that they taught anybody very much about what was important in large glass systems.
Well, they did build, of course, big glass lasers.
They did, I mean, everybody was building glass lasers. Take Sandia; I visited Sandia in those early days, and I couldn’t get over the fact that there was a cardboard box two feet square, two feet high, full of damaged mirrors. There must have been a fortune in damaged mirrors. And these people had a large glass laser system there, and they seemed to be expert in going through mirrors.
Other people specialized in distorting rods, I guess.
Yes, rods and mirrors.
I suppose that was one of the things you could say about AFCRL’s work, in comparison to some of these other projects, is that the element of “cut-and-try” may have been smaller. On the other hand, it might have been argued that you did have access to lots of materials that you wouldn’t have had if you were a university lab.
Yes, that’s true. Yes, I think the dimension we operated under then was one of trying to understand, again, the fundamental factors going on which seemed to dominate the laser’s operation, and the ultra short pulse phenomenon that was found, was yet another manifestation of our attempts to get at what were the dominant factors.
Did you, if you were to identify yourself in this period, you’re an administrator, you’re by training an engineer, you’re doing some fairly fundamental physics here, you’re interacting with industrial research laboratories, with academic research laboratories. Where did you feel your affiliations were? Did you feel if you had a shot at it, you’d like to go to a university situation? Did you feel industrial situations were attractive? Did you feel that AFCRL was the best of all possible worlds?
Well, at the time, I thought, I so much enjoyed what we were doing and it was so stimulating that I wasn’t beginning to think of moving out of there. I was personally very motivated and enthused about all that was going on there. The work itself was so challenging and so rewarding and so intellectually stimulating that it was just a great time.
How much time did you spend at the lab? How much time did you spend with administration?
Well, I was probably spending 60 to 70 percent of my time doing technical things.
In the Lab?
Yes. Basically orchestrating the work of other people, directing the work of other people, hiring people, setting up groups, experiments, looking over what contractors were doing. But my recollection was that I spent a lot of time supervising people, but it wasn’t personnel problems I was dealing with, it was what specifically is going on in experiments, how do you explain it, what else should we be doing with the experimental group that I had. So I would say the bulk 50 to 60 percent of my time was able to be spent that way. The responsibilities I had for contract work occasionally would take chunks of time. I’d go to meetings; I’d occasionally write up things and I also had personnel problems. We weren’t able to compete very well in those days in hiring people, so just acquiring people was difficult. But we were able to do that.
How many groups did you have working for you?
Well, the size wasn’t all that large. It was probably about a dozen people. But doing a number of kinds of experiments, and of this dozen, maybe three or four were theorists, a few technicians, and then the rest were experimental scientists.
Most of the research collaborative, two people working on an experiment, that sort of thing?
Yes. And then we also worked for the Solid State Science Laboratory, in a kind of coordinated sense, trying to understand some of the larger problems of ruby laser systems.
So it would be more like an academic style research than an industrial style, would you say?
Yes. Of course, regarding an industrial style in those days, you’d have to go back and say, what was industry like in ‘63? And I’m sure Hughes research laboratories, while they had a more structured way of getting funds, basically, the nature and style and our communications probably was no different from that kind of a research laboratory.
In an accelerator research laboratory we have groups of 30, 40 people.
Oh yes. No, our experiments were nowhere near that large. We’re talking about efforts taking — we had a good access to co-op students at MIT. That was also very important, for they were a good stimulus and they would often come with no commitments but a willingness to work. Townsend went on to get his PhD from Stanford. It was delightful working with those people.
OK, well, out of this basic research, you wind up writing a paper on applications of lasers which, in several forms around 1966.
Tying together what you’d been doing, the impact lasers have had on the study of materials, including the development of new kinds of crystals and materials, knowledge of transition probabilities, metastable states, lifetimes, general spectroscopic structures of gases etc. I wonder if, looking at it from this perspective, if there have been really important spinoffs from this laser materials research, outside of the laser field, that you would cite today, for example? Given that laser materials are good for making lasers, and presumably you’d cite things like large optical components for other kinds of systems, like Space Telescopes — has this been as productive as say semiconductor materials research has been, would you say or has it been too specialized?
While I think it was quite specialized, I believe it is finally beginning to pay off. I think the semiconductor business is dominated by silicon, but the optics business is much more of a batch process approach. I think it’s hard to argue that a lot of the materials work that was done then had broad universal applications but I think optics is only now being accepted commercially. Having to understand what high powers did to optics probably did a lot in a broad way to influence what was done in materials. We had to clean up materials and that if anything was the more dominant thing that came out of the early work. This probably spread then to non-linear optical materials, to mirrors and other components, with the insistence that you couldn’t be sloppy in their preparation any more, as you were in the earliest days. For example, we used to use silver mirrors on very crude substrates. Well, you don’t do that anymore, for all kinds of reasons. But some of the early work on damage to them really pointed out some of the problems.
We’ll go more into that, probably, but in this other article for a moment you had a very short section on defense applications of lasers.
I’m even trying to think of what article it was. I think this was published as a chapter in a book, too.
Yes, that was the one I saw that came out a couple of years later. Well, when you talk about defense applications you say, “It takes a true believer to accept that it will eventually be possible to direct and focus sufficient energy from the ground at a target in the upper atmosphere in such a manner as to destroy it or even alter its course.” Presumably Charles Townes, Arthur Kantvowitz and William Culver are among the true believers in 1964 when you first put that together. Would I infer correctly from this comment that you did not have a lot of faith in ASAT applications of high energy lasers at this point?
Sure, Yes. I think that’s right.
Did you think that this was a wild goose chase that the DOD was engaged in?
It reflected efforts, I guess in those days, to build large glass laser systems, even starting with ruby at Livermore, but the effort to build large glass systems to do that. And the comment was written really with respect to the possible success of glass laser technology for that application and it seemed like the problems of doing that with respect to those kinds of lasers — because they were the only ones at the time that were being pursued — were enormous. The gas systems when I put that article together probably hadn’t even been thought of.
This was ‘64. Gas systems had been thought of, but none had been reduced to practice, let’s say.
Yes, well, they had gas lasers, but the idea of flowing a gas to take the heat off was not a concept which had been thought of at the time. So my comment was really towards ruby and glass.
So by that time, it was apparent to you and most people in the community that ruby and glass work was not going to lead anywhere. This is about the time that the HELSA study gets going at Hughes which more or less concurred with that point of view, in terms of ABM applications.
Yes, I just saw so many fundamental problems. My comment did not reflect any careful analysis of laser coupling irradiation into aluminum and things of this sort. It was just the immensity of getting such a device to work, from our perspective of knowing what the problems would be, and doing that — that led me to make that kind of statement.
Well, let’s say you were going to SGOM and you had contact with Culver and people like this who were advising on this effort. Did you ever, do you recall ever saying, “This is really a silly thing to be doing” to them? Did you feel that the Air Force was going to spend money on it anyway, and therefore —
Oh yes, it was far above my pay grade at the time to challenge it. It was just part of the general technological development, and people had to argue for some application for large glass laser technology. I was never privy to what arguments they used to give — we can build something which might be an ASAT weapon, or can affect aircraft or whatever. I was never privy to that, but I certainly knew the problems of making a big system function properly, and just on that basis, I was very very skeptical.
Did you have any reactions to the statement, do you recall?
No, I don’t think I did. I don’t think anybody ever said, “Hey, what are you saying that for? Isn’t that counter to what you should be saying?”
It was reviewed, but not so much for technical judgments, or statements. Yes, there were certainly quality control activities on what was published there, but in a technical sense, no.
So nobody in security — you wouldn’t send it around to AFWL?
Well, nevertheless, the fact that people kept building these big glass lasers was going to have an effect on your life. One of the first was the initiation of laser damage studies, which about ‘66, ‘67, I guess, was when you really established a formal program in this area.
At Cambridge Research Lab. And before that time, most of the activity in this area had been going on within the contractors, within the industrial laboratories. Why at this point did you decide it was important to have an Air Force in-house program?
Because of our discussions with Pete Avizonis and Art Guenther at the Weapons Laboratory, and their problems in damage to ruby, and then the generally perceived problems in damage to mirrors. But it was more the fact that ruby at the time was damaging, and again, the fact that we had an interest in the fundamental things which were important in limiting laser operations. Also, because we had the Solid State Sciences Laboratory there, and to the extent that they could grow special materials which might be used as controls or devices, materials to irradiate, that was another factor.
OK, so you had the technology base and they had the need.
But it’s their need which is more or less starting the formal program.
Did you know about or had you participated in or did you draw upon any of the Seaside studies that had been made in laser damage, prior to this time?
No, absolutely not. The thing I remember that first caught my attention was work that Perkin-Elmer had done, I think under contract with Fort Monmouth, and that was just in the open report literature. Then it was, dealing with the Weapons Laboratory, and what they were observing as being problems with large lasers, with higher power laser systems. But Seaside and those documents never filtered down to the level of our laboratory.
Well, it seems to me, about this time, just looking at it from the DOD perspective that the ONR program, the early initiative to see if ruby or glass lasers could be credible ABM systems is sort of dying out. Now people are pretty much convinced they can’t really serve in this role in the present state of the art, and efforts continue at big labs like MICOM to develop such systems, into the late sixties, the faggot lasers, disk lasers and the CGE lasers, etc. In general this all seems to be from the inertia the program has generated from its start. Yet here you are, somewhat of an expert in ruby at least, and you are now committing your laboratory to laser damage study. Are you just saying, “OK, Art Guenther, I’ll do what you want?” Are you looking to other applications of glass lasers using these power levels? Are you looking at fusion already?
Oh no. No. We just knew that obviously Q-switching was important, and you could damage the components if you weren’t very careful in limiting the power density. So I felt this was a problem in the more general sense, on larger Q-switched higher energy per pulse systems. You were very much limited in the efficiency of laser oscillator amplifier systems by the damage phenomenon. You really had to hold down on what you would extract in the way of energy in a pulse, and it was the growing view that, Lord, that’s going to affect the capability of Q-switched systems, and their efficiency. And so we were not driven at all by fusion or the specifics of anything Avizonis was trying to do in application, but of the general observation that these materials are going to be useful in range finders, in designators, and in other smaller systems where the power densities are limited by the same things as they are in large systems.
So the Vietnam situation also has some sort of indirect role here, the fact that these systems are being developed for field use, the increasing emphasis on what are called quick response kinds of uses. Were you involved in any of these applications?
No, No, we were not involved in any of those at all. The Vietnam applications, I had no knowledge of them. We only observed it you know from our discussions and connections with the laser industry, and what the problems were; we just saw it as a fundamental problem in these kinds of systems which limited their capabilities and limited their efficiency. And of course, it was an Air Force problem — and the Weapons Laboratory had these problems. But it was a way we could be useful and establish a way in which a research laboratory could work for a more applied laboratory and help them in some of the things they needed help on.
When they talked to you about setting up a program in laser damage, did they also talk to you about your program; did they also say “We’d like to get these conferences together”?
So this is a later response to the same need.
Yes. The damage conferences just represented a swelling of the activity in that area, and a realization that, hey, why don’t we get together to share mutual observations about it? They also grew out of early work that Art Guenther and Haynes Lee and myself and others were trying to do through the auspices of the ASTM, the American Society of Testing and Materials. We got into the efforts of, how do you characterize these laser materials? How do you measure them? How do you measure them in a way which is meaningful so that persons selling lasers knows how to do it and a buyer can be smart also? So we had meetings of that sort, and I think the Boulder Conference tended to grow out of some of those early associations. But that wasn’t part of our getting into it at the very beginning.
So this is even another separate move from the work at AFWL?
There were some contractual efforts you were monitoring. One was by E.G. Brock and F. Unterleitner at General Dynamics, Rochester, to investigate radiation transfer processes and optical interactions, particularly studies of the effects of photons generated in ruby lasers. Or your particular interest in it?
I think it had to do with excited state absorption processes in ruby which could lead to excess heating and to limiting the efficiency of ruby lasers.
It wasn’t connected with Wolf’s work, then.
No. No. I think they had a few good people with some good instrumentation. But they were concentrating on excited state lasers absorption processes. Ernie is now at Los Alamos.
With the laser isotope separation group?
He was with the laser fusion group at one time, and I don’t know, I think he’s still there. He’s probably more into the intelligence world, intelligence activities.
There was a man named Barone at TRG.
He did theory of laser oscillations, and this was presumably closely allied to the kind of work you were doing.
Yes. Steve was and in fact the whole TRG group did. We were highly knowledgeable of and supported the work of Maurice Newskin and Steve Barone there, and Steve was a bright, quiet kind of a fellow who was associated also with Brooklyn Polytechnics. In terms of resonator theory, I think he probably did some of the best and least appreciated work in the early stages of incorporating the properties of a laser medium and its influence on modes.
Particularly in a gaseous medium?
And the disturbances and homogeneities?
Yes and the effect of mirror tilt. He was evaluating mirror tilt influences on them, and in our view, it was important, but he wasn’t enough of a dynamic guy to make much of a show out of it. But it was very good work.
Was Gould still at TRG at this time?
I think that he may have been, but I don’t recall where he went after he left there. He was I’m sure there in the earliest days, because we were supporting work at TRG in ‘62, I think, and I’m sure he was there then.
So you knew Gould and Goldmuntz?
No, I didn’t know Goldmuntz. Oh, Dick Daly, yes, we knew Dick Daly very well, but Goldmuntz, I didn’t have much association with. You know, we were spending monies with them which would support a low level of very fundamental studies by some of their research staff. We didn’t represent a potential source of money to them which, in a corporate strategy sense, was important.
In general did these contractors look at you as a route to weapons systems development contracts?
They just looked at you as a little bit of source of extra money? I gather that what is happening actually is that researchers in the labs are looking to you.
And the company is tolerating what you’re doing in their laboratories.
Yes. Well, I think, Goldmuntz I’m sure didn’t; he probably was pleased, but it wasn’t anything in a business strategy sense that would deflect him from his much more demanding job, which was just supporting TRG in that kind of environment, a million dollar class, a year.
In the whole DOD game, there is good money that’s going to lead to systems, and there’s still other money that you get, and you were the other money —
— part of the little other money which was going for understanding as opposed to building lasers. We were probably a brighter part of the basic research community because we had a capable group of people inside as well had good judgment as to what basic issues ought to be studied. I think the associations they had with us they probably viewed as important for those discussions, as well as for the money.
We talked about Mandel’s work that you supported. There was work by a man named Toraldo Di Francia in Florence on a stable laser resonator. I’d never heard of his work.
Di Francia? Very famous optician in the world, in the theory of optics.
Yes, mostly classical. He of course developed capabilities in the laser area.
So you were building on his classical optics?
Yes, so we were supporting some of the things that his group wanted to do and did. There were two components to that. I think he was doing some theory which probably Peter Schweitzer was interested in, but there was a guy named Orazio Svelto and Carlo Sacci whom I still see to this day at laser meetings, and they were doing some interesting spectral analysis, rather fundamental work on ruby systems at the time, single frequency generations and things of that support, so we were supporting them through the AFOSR.
Another person was R.K. Chang who studied temperature dependence of Raman light, stimulated Raman effect in crystals, can you tell me about that?
Yes, he was at Yale University, and he was doing exactly those kinds of studies, which we again thought, from the point of view of Raman scattering, would be important. But it seems to me he left there. That work terminated after a year or two or something of this sort, and he left the field and nothing came of it.
Then there’s a man at Cornell, Wolga, who was doing stimulated Brillouin scattering and coherence and a Q-switch to ruby laser emission and laser damage. Now, that name recurs, —
Yes, as prominent in Cornell work. Is there anything in particular about this project that stands out in your mind?
It was a stimulated Brillouin scattering that they were doing and we were interested in, again from a fundamental point of view, what’s the coherence of that stuff? If you used that as a frequency shifter, is it going to be coherent, and I think they measured that and confirmed that it was. In many ways it wasn’t a surprise, but it just added to the information base about what the coherence of that radiation was.
It’s a way again of cleaning up a ruby laser beam through scattering?
No, we were looking for ways of shifting the beam, in terms of looking for frequency tunability. And the question of, what’s the coherence of this scattered radiation, was sort of always one, that needed to be addressed. So with that they just set up a classic experiment to investigate spatial and temporal coherence, and determined that it was just as good as the driving laser.
Would you consider this as support for your own work in optical parametric oscillators?
No, but it was probably part of our broader view and the evolution of work we supported on ways of making laser systems tunable.
Does this become important at AFCRL for any reason? I know that in 1964-65, Avizona and Bloembergen and Garmire and Culver and many many people get involved in stimulating scattering, anyway, and some of these other scattering processes, they are interesting from the scientific point of view, and from the tunability point of view in terms of the technology of the laser, but was there anything peculiar, particular, specific about your interest at AFCRL that would depart from the general scientific interest in the subject?
I think the only thing that did stemmed from the fact that we were members of a laboratory which was Optical Physics, headed by John Garing. OK John Howard was his predecessor. And the idea of being able to move a beam into frequency regions where you avoid atmospheric absorption, and minimizing scatter, as well as to do time-resolved spectroscopy, I saw real potential for that. I was head of a branch in the Optical Physics Lab that had three other branches, and could see that those guys were using techniques which were going to get absolutely outmoded by tunable lasers for spectroscopy. I foresaw if we could develop ways of tuning them, we could get an intense source in time and be able to, with the use of that source, map the temporal dynamics of our temporal energy transfer processes in molecules. Those guys were using non-laser techniques for doing that, and I could see the power of a tunable source in spectroscopy. While maybe the work on Brillouin scattering with George Wolga was one of trying to get a satisfactory answer ourselves about coherence, we became more sold on the power and the utility of a real tunable laser, and that association was driven home by seeing how important and how efficient a device it could be in doing that, because I saw the struggle and the inefficient techniques that other people were using to do spectroscopy, and here we could have a very bright source and be able to tickle molecules and do some other rather remarkable things with it.
Avizonis’s interest in this was very directly related to the cleaning up of the ruby laser beam and getting more efficient propagation, a better quality beam, but your interest in this was more from the scientific basic research point of view. Did the Air Force to your knowledge have a definable interest in SRS that you were responding to in any way?
No. No, they didn’t. We saw it as a way of smoothing the beam a bit. I mean, hydrogen scattering and so forth, I remember that kind of work, and maybe in some ways being a better amplifier, from a device point of view. We look at tunable lasers more as a very important tool which could be used for making other measurements much easier to do with that kind of radiation. Ours was a more broader scientific-driven interest.
Was there any coupling between your work and Avizonis’s?
Not in that area. The area where there was coupling was the discussions with Avizonis and Guenther in laser damage. That was where we were very much coupled together.
I gathered that insofar as this was considered for applications by people like Culver and Avizonis that the advent of the carbon dioxide lasers had put that question aside.
Yes, to some extent, but laser damage still persisted in even low power systems.
Then we have E. Lipworth at Brandeis that must be the man you were trying to think of, who was studying coherence of electromagnetic radiation of the atmosphere and nuclei induced by major excitation. Do you know what that means?
No. That was a Peter Schweitzer project. Peter was a very fertile kind of innovative fundamentally driven mind, and I had very little to do with that.
As far as you know nothing tremendous comes out of that.
Do you remember other contractors of particular significance in this period that you supported that I haven’t picked up?
I would say we supported work at MIT for years and years, and —
Javan’s group and Townes was a member of that group early on; when my group was moved into Optical Physics, we found John Garing supporting work by Townes, just generally giving him money. Then, with more applied money that came from Wright Field, I began supporting work that Javan was doing, and we supported that for a number of years, over the latter part of the sixties. And the real thing is that Javan developed what was probably the best group on the East Coast, producing graduates which would go along to help develop other U.S. laser capabilities. And of course they were doing Brillouin scattering and things of this sort, Garmire and Ray Chow. A project I got particularly enamored over was the following. Javan was a spectroscopist and he needed tools to do high frequency spectroscopy, and so he developed techniques for using point contacts for detectors, with very high band widths, and so I got enamored with that, which in the long run probably was a mistake, but anyhow, we supported work with him for quite a while. The other projects we supported were in the tunable lasers, with Steve Harris and Tony Siegman, and I think that probably, at its stage, and looking at what’s important, that probably was the most important work that we funded. I would also say the Rochester work was exceptionally good and helped to clear up what was going on in ruby systems. With Steve Harris and Tony Siegman, it was the first work on optical parametric oscillators. And the students that came out of that went on to be key staff in new companies and establish the tunable laser capabilities.
Now, in this business of supporting, of course Seigman’s work is very significant as is Javan’s, but in terms of Javan’s work, this is not unrelated to the work that was going on at this time at AVCO that was producing gas dynamic lasers and nitrogen lasers and things. Were you aware of that development?
…hard but it was pretty hush-hush nevertheless?
Not especially. I was aware — let’s see. I was aware of it but not really part of it. I can remember, I was the chairman of the 1967 laser conference, DOD Laser Conference, and that was the first time that AVCO guys were allowed to talk about some of that device work.
Was this your first awareness?
It’s hard to say. No, I don’t think so. I mean, from my Special Group on Optical Masers, I’m sure I was aware of it. But it was the first meeting of contractors where it was discussed. And I knew Javan was consulting with them. But knowing that what he was doing had any particular connection with what was going on at AVCO, I did not know that. I don’t know today if it had connection.
When we broke off we were going to talk about the Third Conference on Laser Technology and I’ve been intrigued by these Conferences on Laser Technology because it seems to me that within the classified defense work that was done by the Department of Defense there has been a felt need for these kinds of forums, which are in a way a simulacrum of the larger scientific community, in order to bring people together to talk about their work.
And I was wondering, since you were a program chairman of at least one of these meetings and participated in a number of them, if you could comment on the sorts of things that were done. For example, were the papers refereed as they would be in other scientific conferences?
Well, the organizers usually consisted of the senior laser program managers of the different services; clearly Wright-Patterson was always on it, ONR, ICOM, AFWL, and so forth. But I would say in terms of refereeing, it was only done probably in the stages of organizing the meeting. These meetings usually reflected the interests of the contract monitors in seeing their people perform in that environment, and usually those people who were contract monitors were also in some way associated with organization of the meeting, so it was usually always connections of that sort. So I’d say, refereeing really wasn’t done, but only in session with this kind of a title, and refereeing done only on the basis of shared perception of the quality of the work that was done there. I think, as to the utility of those meetings, I’ve always been sort of skeptical, but I have to say fairly that I really wasn’t a part of the classified work that went on in the DOD. I was kind of aware of it, but my own activities were not, as we’ve been discussing, at the central part of a lot of the classified work. I’m sure those meetings were good for the people who gave papers, because otherwise they really couldn’t do it, it really was a forum for those people to meet and discuss things. As in most contractor-dominated meetings, I often wonder how much discussion you know really goes on, because they don’t want to give away any information between themselves. Things are tighter these days and less of that’s done. In 1967, it might have been better, it probably was.
Were there informal ways of exchanging information that were promoted in these meetings?
At the usual scientific conference, the really important stuff doesn’t take place up on the stand; it takes place in the halls.
Well, sure. That kind of thing, of course went on. But I think it was still done in a guarded way, because you’re still talking about classified information, and there was the need to know which was the second thing you had to be concerned about.
You talk about proprietary information and classified. In this particular conference, the third one, which is when Gerry talked about gas dynamic lasers and Herzberg talked about Boeing’s project for closed-cycle GDL’s, both of these had to be published at the end in a separate little pamphlet, apart from the rest of the proceedings of the conference, because of the proprietary considerations involved. I’ve asked this question before and maybe you have a response to it, to what extent was it in the interests of the contractor and to what extent did they try to classify information when they thought it would help protect it, in a proprietary way? Do you think that was happening at all?
Oh, sure. I don’t know who they viewed as their competition, but surely that’s a ploy for wanting to do that. You know, Boeing and AVCO talking that way reflected the trade-off of them wanting the publicity versus giving it away in the public prints which would go to everybody who attended the meeting. That was a real hassle. I can remember many many hours on the telephone in my office at AFCRL wrangling with Kantrowitz and with the Air Force staff people here in the Pentagon and just trying to work out how we were going to handle that.
That particular problem.
Yes. But it was bigger than that. It was also just the presentation of it, how should it be handled, who should hear it. It was clearly the proper handling of those issues which were a real problem.
At the time did the Gerry work and the Hertzberg work seem of comparable significance? In retrospect, Gerry’s work looms large and Hertzberg’s was almost forgotten. He wrote programs and developed them at Boeing which didn’t really go anywhere. But at the time do you recall if people were equally excited about Hertzberg’s stuff?
I don’t think so. My own perception was that what AVCO was talking about was the most important because it represented direct laser work, with some kind of a working laser and it seemed to me Boeing’s, whatever Hertzberg was doing, it’s very fuzzy in my mind, didn’t have that feature about it which clearly attracted everybody.
Well, he was taking the gas dynamic laser and recycling the reactants.
Yes, but it was proposal, wasn’t it?
Yes. They later got into it, but they had not then.
I think most were excited because AVCO had a laser, and that’s the difference between having a laser and proposing some refinement, important though that might be — the attractiveness, the attractive thing was just this, the flowing of the laser working medium.
Well, you also had a night session to talk about the nitrogen carbon dioxide laser at that meeting. It was an unclassified thing. You make a point of it in your preface. I just wondered if that discussion was in any way significant.
Yes, I think the reason for having it was because they were doing it at Bell Labs on small tubes. We were interested in taking it to much larger sizes, and some of the dynamics and kinetics going on in those kinds of lasers were clearly very important to the DOD, but yet not classified. And so that was as much the motivation. So whatever that session was, it was one where people could not, or shouldn’t talk about classified stuff but should keep it unclassified, on a fundamental basis.
Now, the Raytheon sewer pipe lasers and that sort of thing, were those unclassified at that time?
I honestly am not sure. In the Army, I guess they had a 178 foot gas lasers and even longer things at Raytheon?
And AVCO had some money in that too.
OK, well, this was along your later acts when you were at the Cambridge Research Lab, and before we take you to ARPA you might want to comment on the effect of what you did there. I know that Howard Schlossberg came then when you left from AVCO.
I went to DDR and E in early 1970, and spent six months there, went back to AFCRL for just about a year, and then went to ARPA.
Well, did he more or less take over the group that you put together?
Yes, he took over as branch chief for the group that I put together. That happened about 1972, I guess. I decided I wasn’t going to come back so Howard took formal responsibility for the group. AFCRL reorganized a bit. And Howard went off to the Sloane School of Management some time or other. He had problems there, for one reason or another, with the upper management of AFCRL. And by that time I was at DARPA and didn’t have much time to worry about that.
You said earlier that you felt that the group had somewhat dispersed?
Well, the work on laser damage certainly began to. I remember convincing Erlan in Bliss to come from Pittsburgh as a young PhD, to give up spin waves in bismuth and come work in his Air Force career — he had three years to go in the Air Force — to come work in the laser damage area. David Milam, I remember recruiting from the University of New Mexico to come and work in this area. And so I built up a group which probably became the most competent one in the DOD in fundamentals of laser damage, especially looking at how to do experiments. That was a big issue, how do you get a handle on this and what was going on.
Was this a standard method of recruiting, get people when they’re serving out their ROTC commitment?
Well, that was a big plus that AFCRL had, because it was a research laboratory where people of that sort could be assigned and do research. So to me it was the best place to spend one’s several year career in the Air Force.
But how hard was it to arrange for this sort of thing? I know that AFWL at this time had serious difficulties, because if you had officers, for example, every two or three years they wanted to send them to another assignment, and at that point it didn’t make very much difference to the Air Force whether your career was technical. So did you have trouble getting the people you wanted and holding them once you got them?
Most of them were not committed to a career in the Air Force. Bliss for example was a new first lieutenant, spent three years and got out. There were three others however that were part of my group who began their careers there and went on to become bird colonels in the Air Force. And to some extent, it probably was not a good assignment in their career, because it was doing just quite fundamental work and it wasn’t connected with the mainstream of laser activity necessarily which was certainly at the Air Force Weapons Laboratory. But I guess I want to comment that the work started at Hanscom Field, if you look at what came from it, I think the early work we sponsored on the tunable lasers with the Stanford group was seminal work. I think we probably organized one of the best activities in the laser damage area. But that seemed to dissipate after I left. Bliss went to Livermore. David Milam went to Livermore and because basically the problems in laser damage, loomed enormously with fusion lasers, and so those guys left AFCRL. Howard Schlossberg took over, and I don’t know what all went on there, but anyhow I saw those two guys leave, and they represented the core of the laser damage capability at AFCRL.
Well, to what extent did this have to do with the fact that glass lasers are becoming passe, big glass lasers, in the services at this time and becoming of interest to the DOE?
I guess it’s a combination of that. Big glass lasers are becoming passe for use as weapons, but power densities are just as large in small lasers as they are in big lasers, and the damage phenomena were still prevalent even among small lasers, and so we were still prevalent even among small lasers, and so we were concerned about understanding why that was going on in glass as well as ruby and non-linear optical materials.
OK, but that particular problem, you could pursue in the DOE as well as the DOD.
It’s the same problem. There is certain sexiness to that high energy laser work, I think, that is not there when you start talking about target designators and range finders. That was really not the kind of work that if you are hot stuff, you want to spend the rest of your life perfecting the neodymium laser range finder for the Army.
Who mainly is concerned that the first lieutenants don’t drop it and break it — you know. So I just wonder, you know, the glamour really is going into other areas.
Yes, certainly, it certainly was. It was certainly going into the DOE areas. But you know, in terms of people moving, there are other things which influence their careers, and those other factors could have been present there too. The group was sort of committed to understanding things on a fundamental basis, and I think that clearly the DOE laboratories were growing in this area and represented a very attractive possibility to people who had capabilities there, so Bliss and Milam left.
Now Guenther, of course, we referred to his initiative in getting you into the laser damage field in ‘66, ‘67, — to what extent did his activities at AFWL contribute? Obviously he organized a number of activities or helped organize them, but was he doing important work at his lab? Was it a center of research on laser damage?
Art specializes in very careful measurements. I recall that his work was helpful in trying to track down some mechanisms. But it was almost out of balance, from the point of view of time and effort spent into measuring pulse energies to three significant figures. Art’s bigger contribution was just in his position at Air Force Weapons Laboratory, his importance there, his stimulation of this community, the damage meetings themselves, and his hard driving nature, to get and keep them running.
So if we are looking for an in-house capability in laser damage studies, as we have defined it, which is something that is peculiar to high power density lasers, then you would say that Cambridge Research Lab provides that first real in-house capability?
I’d say, it just provided a beginning of that, and the people. No, obviously, our goals and motivations of understanding it were somewhat different again, from a more fundamental point of view. Art characterized carefully the performance of big systems and their limits. Again, AFCRL had the materials capability, which allowed us to try to understand the effect of occlusions and things of this sort. So I guess it’s just more important in the training of people, and I really think that the whole DOE complex, if you look at it, that the whole DOE complex benefited from the DOD, not by the hardware that was built but by the people who were trained.
One could make a similar argument about NRL. If you look at the Livermore Lab laser group, many of them came from the Naval Research Laboratory. They weren’t necessarily engaged in damage studies there, although people like Glass did things, so I have been thinking that the primary resource for the DOE programs in glass lasers have been the Naval Research Laboratories.
I think that’s probably true.
What you are saying is that a secondary resource of importance was your group at AFCRL?
Yes. Certainly a lot fewer in numbers, but I think the people left my group and went to Livermore trained to do some very careful measurements in the damage area, and understanding of those. And David Milam forms the core of the Livermore capability to characterize, still to this day, through pulse and other kinds of damage phenomena in the materials.
Of course, you don’t go to Livermore. You go to DARPA. Why is that? I mean, why did you go to DARPA?
Oh, when I went to DDR and E for six months, I happened to run into some of the DARPA people who were also in the Pentagon. They were at the time being pressed by Glenn Sherwood, from the STO-Strategic Technology Office, to look at the materials problems that there were in these large glass laser systems, and the basic issues of what was going on. And so while that was dying in a national classified laser setting, it was sort of dying down in importance relative to the GDL, it still existed as a real problem in those materials, and so DARPA elected to initiate some contract programs to try to get at what was going on, in glass as well as in ruby.
So this is Sherwood’s initiative?
Well, Sherwood was twisting the arm of the Materials Science director at the time. But anyhow, when I was at DDR & E I met these people at DARPA, and I got talking with them about what I did in a personal way for my own research, and at the time, part of that was the damage phenomena in materials, and so, they had nobody at DARPA at the Materials Sciences Office who had any knowledge about that, and so one thing led to the other, and they offered me a job there, and that just sounded like something I wanted to do with my career, at that point.
I guess you came about the same time as Gerry came, to replace Sherwood.
And Dave Mann was his boss.
Could you tell me about the relationship between you and them?
Personally, and between Ed and I, it was very friendly, but Dave Mann ran a very closed, secretive type of operation, and within DARPA, there was very little connection between what one office did and the other. It was just in the interest of organizations maintaining their own program and doing their own thing, and so with Dave, there was no communication. Regarding Ed, we saw each other socially and talked about things, and the important thing I guess that did happen was Lukasik, the Director of DARPA, finally saw that there were materials problems that Dave Mann was having which he certainly wasn’t suited for coping with. At the time, I had gone to work under Sinnett. The Deputy Director of DARPA then came to us and said, “The laser guys need help in the materials area,” and basically it was windows. How do you get these CO2 laser beams out of lasers? And so the bigger effort that I began getting into then was the whole business of infra-red optical materials, and so Ed and I would talk, but basically there wasn’t much influence on what we did from those friendly discussions. There was some influence programmatically through the director’s office on what we ought to do.
So you worked really in tandem on those two programs. He was operating independently and your coordination was from the top, rather than in an informal way.
OK, this DARPA window program I relate to the study that you had at Cape Cod.
I guess it was the Materials Research Council in 1972. Apparently, at the meeting, Bloembergen got up with the Bloembergen hypothesis about the change in dielectric field strength and the presence of occlusions and pores and cracks in laser surfaces as a possible source of the damage that was being observed. In your presentation to the subsequent Boulder Laser Damage Conference, you indicated that you thought this was a significant theoretical breakthrough that might lead to real progress in what had been largely an empirical program to this time. Can you comment on that?
Yes. The flash of light which struck him there was that there’s a focusing effect of the electric field; when you have dielectric discontinuities and changes, and — well, for example, I think at that meeting we were talking about surface breakdown, and it appeared that there would be a connection between the present of inclusions and scratches and digs, through this mechanism he suggested. So it provided a link which seemed extremely reasonable between observations of damage distributions, and surface quality, and it seems to be a link that people hadn’t really thought about.
It seems rather obvious in retrospect.
Yes. All things which are probably right are to some extent obvious in hindsight. But somebody has to think of it first, and he was the first one to point that out. Now, there has been lots of discussion which followed, after years of better measurements, by Dave Milam at Livermore and Bloembergen and his students at Harvard, which would tend to indicate that different things and other things are important. But that was a seminal thought at the time, in terms of providing some theoretical guidance as to what was going on.
And you were definitely looking for that at the time, were you?
Yes, we were looking for it. We were trying to say, what’s going on in these windows and what might be some mechanisms? We were also looking at what can we do to increase the average power through these kinds of windows. So I think the meeting in ‘72 had both these kinds of things going on. We were looking at techniques for making windows, what’s dominant in them causing damage, and what’s the limit to the average power and can that be increased? There’s also Bloembergen’s observation about pulse damage.
I thought it was a very interesting session, because it was sort of a watershed in the laser damage business. Before that time, what you had was sort of increasingly sophisticated attempts at quality control, casting about for meaningful parameters, but it was really largely cut-and-try. You can measure the things better, and maybe this will help you, but basically there seems to be no real good pointer as to the direction in which you might go, and this seemed to, whether or not.
It provided a very good pointed, whether or not it really was it in the long term, or covered all bases, I’m sure that it didn’t but it provided a focus for —
Do you recall that other people in the field who were equally excited about it?
Yes, certainly in those years. And then later measurements came along which tended to say, hey, there are other things which are going on. So some disputes broke out in the field.
It seems at the time to have been an important rallying point.
It was the first substantive theoretical pointer which seemed to make some sense.
OK, now, I have a bunch of questions, I guess, that I’ll put more or less in chronological order through these DARPA programs. This is based on your own writing.
Good basis for them.
One of the earliest programs was run in December, ‘71, to fund a program at NRL to investigate preparation of alkali halides, which I gather were the most promising window materials at that point, by press forging, and also to investigate weak absorption mechanisms and development of protection coatings. Why NRL? What comes out of this program?
NRL was funded early, I can guess, for several reasons. First of all, they were local, and therefore had always been close to DARPA, in the sense of approaching DARPA for dollar support for their research, and I can remember going there to give a talk to the NRL group on plans and programs that I saw coming in the material sciences. Secondly of course they were a government laboratory, and I saw them as having a different role than the industrial organizations, and I didn’t see them as competing in that sense. Most important, I think they had a very strong capability in alkali halide crystal growth. They’d worked for a number of years in color center work, and they knew aspects of processing and growth of alkali halides which I thought were important. That’s the work of Phil Klein. They also had Marvin Haas there, a good applied theorist who would be, it turned out, an important contributor in understanding fundamental absorption mechanisms in alkali halides. So I think the most important reason we funded them was that they were not part of an industrial operation, and I didn’t see them in competition with others, and we could fund them just directly.
Subsequent to this then you organized this ‘72 summer meeting, in which you bring in a number of industrial and governmental laboratories to talk about the materials program in DARPA. Can you tell me something about how this was put together?
I’m sure I worked hard to put that meeting together. MRC meetings, typically might number six or eight during the month, and I know that some of those meetings reflected other desires for them. That particular meeting was one I was very high on myself, and worked with Bloembergen to put it together. So it came about through discussions between myself and Bloembergen, as well as other Defense Department people like NRL and AFCRL, who recommended that specific organizations be contacted, organizations having good capabilities, in the view of these other government people. I’m sure I had at those meetings people from the government laboratories like AFCRL and NRL as well as potential industrial contractors. And I’m sure not everybody who later submitted proposals or was funded was at the meeting, because these meetings were typically held say a year before any contractual action might get under way.
Did you say there were six or eight a month?
Oh, yes, the MRC meetings run for a month, and there might be six or eight sub-meetings which go on during that month.
Oh, I see. So it was one month out of the year.
Like the IDA summer study.
Like the Jason Activity, only its basic physics and chemistry and so forth of materials.
How long have they been running?
The first one, I think, was 1968.
Oh, so they’d just been established; as a result of this laser material problem?
Or this is across the board?
This is across the board in materials technology.
Now, I would have assumed, however, that DARPA would have been interested in materials technology from its origins in ‘58.
Why was the Council only set up in ‘68?
I think the Materials Sciences Directors, were looking for better ways to couple the university community into Defense Department problems. So one of the real goals of the MRC was to do that, and to get some of the best research people from the major universities and bring them in, to see if they could help on problems which the DOD had, and at the same time, by exposing them to these problems, they could perhaps go and start research programs in areas of importance to the DOD.
Apart from Bloembergen, who else from the university community was on this?
Let’s see — Rob Thompson was the Director for Materials Sciences and started the MRC. Rob Thompson was the Director, three people before me. But he came from Illinois. There were people from Cornell, Harvard, Stanford, MIT, Penn State, and these were people who had backgrounds in fracture mechanics, chemistry, metallurgy, and the core components of materials sciences. Optics and electronics was not at all well represented in that early group of MRC members. Bloembergen was probably the outstanding and key person with a background in lasers and optics. I built up the MRC to basically have more members in the optics and electronics area. But Bloembergen was a key then.
I guess one might almost say that materials science conceived of as an independent enterprise, interdisciplinary enterprise, was a little bit older than lasers.
And the late fifties, is when I know DOE took a real interest in establishing centers. I know particularly about the LBL materials science division, IMRD at that time, now MMRD, and there was a center I guess at University of Illinois.
Well, DARPA of course has established the inter-disciplinary laboratories, as they were called, at 12 major universities in the country, and funded them, from about 1960 or ‘61 until they were transferred to NSF in 1972. The transfer was initiated by Sinnott and I continued to work that transfer during my —
— is this Project Themis?
No, entirely different from Project Themis.
I thought that Themis was something different, but I was trying to remember when they were talking about Themis. That was sort of a direct funding project for smaller universities?
Yes, it was a brainchild of Don McArthur who was at the time the Deputy Director of DDRIE for Research and Advanced Technology. He and his staff there came up with Project Themis whose objective was to give support to the other universities outside of the big dozen or so, for innovative ideas.
Sort of an articulation of Lyndon Johnson’s spreading to wealth?
Yes, but it seemed to come at the wrong time. It came a little too late, and the Mansfield Amendment descended upon the Defense Department, and lot of the project Themis work was brought into question; money got tighter, and it just seemed that there were a lot of things wrong with the time phasing of the Project Themis work. Regarding the IDLs, on the other hand, were the basic stimulation for their transfer from DARPA to NSF was the Mansfield Amendment, that is the relevance argument, and also the fact that they had been funded by DARPA for 10 years and DARPA was seated to start new things and then transfer them to others. There was the recognition that the IDL’s had become very important institutions, and NSF then created a materials office, to fund these laboratories that DARPA had started as the core of the Materials Sciences Office.
Well, it’s important to talk about the contribution of from this earlier attempt at material science, which I gather, comes out of a different area, particularly the DOE interest, ABC interest in reactor techniques and also the military interest in exotic materials for various aerospace applications. It’s now being brought in some systematic way to bear on the problems that you had in laser materials, so you’re taking the existing apparatus, and refocusing part of its work on this particular problem of which you’re aware. We’ll be talking about laser materials, but whoever listens to this should be aware that the material science program at DARPA is much broader.
Oh yes. Yes.
Within that context, then, after the ‘72 meeting, out of 17 proposals that you received, you chose eight. In your document that you have before you, which your memo to the Director, Program Management, you talk about some of them. One of them was with another in-house Navy laboratory, the Naval Weapons Center, with Donovan and Bennett to study covalent elements and Chalcogenide glasses. Can you tell me about that particular group and why you were interested in them?
A year and a half earlier, soon after I came to DARPA, I had received a letter from Harold Bennett outlining their capabilities and interest in a fundamental characterization program of optical materials and optical surfaces, especially surfaces, and so prior to this January ‘73 memo, I had involved Harold Bennett and others on his staff in organizing meetings with me, to get this program going. The specific proposal funded by Terry Donovan represented an extension of work which was currently going on. You can see it already had an ARPA order number. And I’m sure we were already funding work at the Naval Weapons Center under Harold Bennett on aspects of bulk materials and scattering in them. And this represented an addition to their effort to look at the specific aspects that you read in that memo. They had by far, hands down, the best surface scattering and basic scattering characterization capability of anybody in the United States, and they were anxious for more work and recognition, and I was willing to give it to them because they seemed to have the technical capability to follow up on that.
I wonder, in the spirit of the Mansfield Amendment, if they weren’t also interested in finding some applications for their expertise?
Oh, absolutely, absolutely. I’m sure. They had approached optics and scattering, from Bennett’s education at Penn State, and I’m sure they were driven by the Mansfield Amendment as a motivating force as well as a funding source.
Yes, I know that when I spoke to Bennett, that in the sixties they had a largely fundamental research program in optics which he got money for, and no one thought they’d have applications, and it’s about this period when I think he began to realize that to survive in the world of military R and D, he had to find reasonable applications for what he was doing. Another government lab was Lawrence Livermore Laboratory which, in which a man named Kahn was commissioned, I guess his name was John Kahn as I recall, to do a study of vacuum surface cleaning and coating methods. Now, I guess he sort of faded from the scene in the interim period. I haven’t been able to follow him very far from there. But you mention earlier that Lawrence Livermore had earlier experience in this game, so was that the reason they were picked?
No. Kahn came out of the chemistry division at Livermore. And he was an impressive fellow in his knowledge of surfaces. In fact, I think the big plus that I saw for him was that he seemed an honest-to-God surface physicist who claimed an interest in optics and the problems that we were looking at with optical surfaces. He had significant plans for building an apparatus within the chemistry division at Livermore for working on our problems, and it was a program which sounded great but never went anywhere, because Kahn, because of his personal work style, just never got down to producing answers. He was perhaps more of a builder of equipment than an answer producer.
No, the third in-house lab was AFCRL. Maybe I shouldn’t ask you why you picked that one; you had confidence in your own people. Posen, I gather, was one of the people who worked with you there.
Yes, Posen was a good fellow who knew the community well, who knew characterization techniques, and who had a group under him; they were agents for a large part of my contract work, and it was important, when they were agents, to fund them to do some of the work themselves. I of course knew them from my years at AFCRL, and when I got to DARPA, I realized even more how unique they were. I realized the uniqueness of NRL and AFCRL as being two of the best government laboratories in this particular area.
OK, the fourth sort of ringer that is in a sense non-player in the contract game is Penn State which, under Knox, you brought in to study coating techniques and characterization of surfaces and coatings. What was the background of that choice?
Rusty Roy, who was at the time the head of that laboratory, was politically quite active, an extremely competent guy, and had been forever bitching at ARPA about lack of supporting Penn State as being one of the interdisciplinary laboratories. So there was a political door open for him, for that reason, but, in my discussions with him, he made me aware of Knox’s capability, and that was substantiated by AFCRL who knew the Penn State group from the crystal growth work. Thus that work was supported at Penn State. To my knowledge, I don’t really think it amounted to much.
OK, now, the other players are all established in one way or the other in lasers — Raytheon, North American Rockwell, Honeywell, Hughes, are not names that we would be necessarily surprised to see on this list. Perhaps we ought to ask who was not on the list. Who did you reject, if you remember at all?
I think one of the ones we probably rejected was Battelle. They had a hot isostatic processing at Battelle which they always were after me to support, and I guess, given the necessity for very low amounts of impurities in these materials, I never supported it. Anyway, beyond Battelle, no particular organizations come to mind. I’m sure there were other universities in there.
Did you make these decisions on your own? Did you have a review board, a materials research council?
No. I probably used the agents. I think I certainly used AFCRL, the Judgment of Harold Posen and company at AFCRL, but I was the one who basically signed the selection justification memo. And I basically selected them based on the budget size, their fit, their total consistency with each other, and the quality of the groups which were going to participate.
Now, was it your intention to coordinate all this work in a strong fashion?
It was my intention to use the agents, for the industrial organizations, to help in the coordination of it. Again, AFCRL would be a principal one. For Honeywell, the contract was an add-on to one I funded directly to them through DSSW in the Pentagon, which has no technical competence. The others funded were government laboratories in which the money went directly into those laboratories so most of the coordination was achieved with AFCRL.
So this is, in a sense, just as AFWL becomes a lead lab in certain aspects of high energy laser business, particularly for the Air Force, and ONR before it becomes an agent for ARPA - -
— sure, it’s the same kind of relationship.
To go into more ethereal realms, one of the early programs you started in conjunction with this was the program with Marshall/Sparks at Xonics, Inc…
— yes —
— to provide a field a theoretical capability, a way of analyzing what was going on I guess at a level where you could get some insights into the basic processes. I’ve read your justification of it, but I’d like you to comment for the tape on why you selected him as opposed to someone else.
Marshall was an outstanding theoretical physicist whom I found to be extremely responsive and very interested in tackling the kinds of practical problems that we were trying to get answers to, the practical problems that the program faced his capability, and his efficiency. He was extremely productive, had excellent insights and I just found his general capability was far and above others that I knew of at the time. He has developed, basically, a superb track record in that community, and was one of the real contributors to an understanding of, let’s say trying to elucidate the fundamental mechanisms which went on in breakdown of these materials.
He’d been studying this at RAND before he set up Xonics?
Yes, he had been at — RAD had sic’d him on this problem, because RAND, through its top level connections with the Air Force, became aware of the materials problems, and Marshall had become aware of them, and was assigned by Rand to work on them. At some point, Marshall left Rand and went to Xonics, and I guess that was perhaps about the time that I started supporting him to do this work. His reports are in a bookshelf over here. He was prolific to a point where it’s hard to digest all the information that he could produce. Excellent man.
I’m interested in the way his program seemed to follow the interests of the laser program of DARPA. In other words, he starts out in the IR, and as DARPA begins to move into the visible and UV and X-ray laser interests, his program seems to follow that. Was that intentional?
Oh yes. I got him going early on areas which I thought were going to need attention, and he would help me to sort of scope them out a bit or understand what the issues were in those areas. So he was studying things in visible materials well before there were any programs in there. DARPA never has done a whole lot in the visible spectral region, but I got him specifically out in front of everybody else, so that when I developed programs later in those areas, I’d have somebody with some basis of knowledge.
But were you aware that DARPA wished to move into these areas?
I could just see it coming. I mean I could see from the way laser technology was going that as new lasers, as the KrF lasers came along, the excimer systems, they were burning mirrors up left and right, and it was a different class of materials which would be used for those, and so I got Marshall looking into those fairly early on. So I could see that that would be the way or the direction for DARPA materials programs to evolve.
Could you characterize the sort of results he got. The kind of theoretical characterization he was able to make in these areas?
Well, his contributions in the infra-red area were to parameterize the whole process, in terms of absorption coefficients of the laser radiation, strength of the materials, lensing which is induced in the materials, non-linear thermal expansion of materials and their cracking, and the degree to which this non-linear expansion exceeds the real strength of materials. He was the one who just sort of was able to get his arms around all of that, and articulate that, to the people in the community. He was able to develop “performance specs” based on optics deterioration if these specs weren’t met.
But he is basically using experimental results as the basis of his analysis?
No, he was using very very basic fundamental physics calculations and he was predicting what these specs should be, and then he’s looking at measurement results and trying to connect those with his theory. He could model things, but whether or not those materials were ever made to correspond with his model was always doubtful. Secondly, there is always a problem of smooth Gaussian laser beams in the use of such experiments. So his model again served as a guide. It served as a way to trade off different things. You trade off absorption versus yield strength, to try to look at new materials candidates for these applications, and see how they might fit, see what kind of candidates they might be, if you could make them that way, trading off yield strength and absorption and other characteristics of the materials.
Well, take a typical example: what do you usually start with? What parameters are usually available to you? You’ve got a piece of material here that some company puts out. Some company comes up with a new kind of laser glass, for example and you say to Marshall Sparks, “Well, what about using this compound?”
He would look at it. We’d look at what the thermal coefficient of expansion would be, and with a little bit of maneuvering these parameters, you could convert percent absorption into B focusing, and that was the strongest, highest figure of merit that you dealt with, and so, knowing the thermal distortion parameters, and connecting them with the absorption, was the most immediate way. There were some glasses and some host materials which are horribly sensitive to thermal changes, and you just knew you would never want to develop those as materials. There are other combinations of alkali halides which have very low thermal distortion, per unit degree C temperature rise, and they became the ones to focus on. You could also say, two photon absorption processes were something that forced you to want a band gap for the materials to be sufficiently large relative to the laser wave length, so you didn’t get into problems of that sort. You wanted to identify impurity sited in the materials, so you didn’t want them near the laser transition. So there were a great number of ways of looking at materials to say, hey, that’s going to fail for this reason or the other: moisture susceptibility, hardness, surface hardness, there’s a bunch of practical things of that sort which you would also collect and weed out. So it was analyses of that sort, a collection of that kind of data, which was very useful to the community, and also just looking at the periodic table. You could look at the periodic table of chemical elements and see how you might put materials together; you could correlate the properties on the table and see what was the direction to go in the area of very very light materials, base materials — you could also do that and that was useful too.
How did you use that information? You say it was useful. Did you yourself use it? Did AFCRL use it?
Oh, we all used it —
— in the selection of projects?
It wasn’t that direct. Everybody became aware, anybody who attended these meetings, the damage meetings, the meetings I held. It was just open information. I just helped educate everybody in the community, as to what’s important in these kinds of processes and materials.
So you were really interested in the research that came out of this, rather than it serving as a guide to monitor contracts?
Oh yes, he was not a guide or monitor of contracts. Sparks was a guy who produced efficiently and quickly, some of the important insights as to directions to go in materials development, and what to stay away from.
There were three other schools that got some money from you, early on, for IR laser windows. One was USC, the others were the Oklahoma State, and MIT. I guess USC and MIT are easy to understand, perhaps Oklahoma State not so?
As I sit here thinking about it, MIT is not as easy to understand as the other two.
USC represented a sort of a unique opportunity, with a presence there of people who knew the laser business, John Marburger, Bob Hellwarth, and guys of this sort, along with people in the materials science community who had laser and optical backgrounds. And the USC activity, then, represented the coordinated funding of a number of efforts on crystal growth, on preparation of materials, surface preparation, a whole host of subjects involving at least a half a dozen or more professors at USC, and all coordinated by Jack Marburger. The quality of it was as much Marburger’s capability to pull these diverse people together, and his own competence, so it was a fairly unique group available to the DOD. They educated people in materials science who had also been hired by AFCRL for example in their Solid State Science Laboratory so there were good links between AFCRL and USC, and it made a very sensible thing to do. At Oklahoma State, Bill Sibley had had many years of experience at Oak Ridge before he went to Oklahoma State. He went there to set up a crystal growth group to develop new techniques there for crystal growth to eliminate color centers. We look upon him as a source of raw materials, and crystal growth techniques which would probably be as clean as you could ever get, from the point of view of not having the impurities in them which would lead to color centers. I’m not sure what in the world went on at MIT. I think it may have been efforts in cadmium telluride, as a 10-micron material.
I think that’s a little later.
Is that a little later? So, it escapes me as to what MIT did. It may have been a characterization capability, but it doesn’t occur to me as what it was.
This had to do with alkali halides.
I’m at a loss for knowing just what they were there for except as I said, as a characterization capability to back up the capability which Harold Poseu had at AFCRL.
It occurred to me that there might have been a connection between these academic efforts and industrial efforts at Hughes, for USC, and Raytheon for MIT.
Yes, USC certainly fed Hughes personnel and they did interchange ideas through consultants, these limits were important. MIT also fed AFCRL. There were linkages in the characterization activities; Hal Posen and his group supported work at MIT in materials characterization. So I think that was probably the reason.
OK, well, this of course was the early windows program. Salt windows were used for the high energy lasers or tried at this time. As we look back from this point in time, what happened with high powered laser windows? The answer might be, nothing happened with high powered laser windows. That is to say that the Airborne Laser Laboratory flew the aerodynamics window, and to my knowledge, there is no high power laser window at this point. What did this program do? Did it fall in the sense of the implied application envisaged?
I think that the ultimate transition of a window to the Airborne Laser Laboratory basically had difficulties from the point of view of handling a large piece of optical material like that in that kind of an environment. It probably ultimately was a better engineering decision to use reflective optics where it could be done, and hole couple through a gas medium than to fuss with, let me use that phrase, fuss with an optical window. And that was a sort of an engineering judgment made by those people. It turned out that the program was far more successful in our view than we ever thought it would be at the outset. Dave Mann’s people came to us saying, “Hey, we need help here. We don’t really think you can help in the long run, but the director of DARPA says these materials guys ought to be helping you in some way on this.” The thought that we could get materials with 10-5 absorption coefficient was amazing to us, and to the community. And ultimately these materials have found their way into the whole laser fusion program, as well as other areas. The capability today of infrared optics stems from work that DARPA supported in fluorides. The fluoride materials today are among one of several candidates for excellent quality infrared optical materials. Others are zinc sulfide and zinc selenide which are made by Raytheon. Without these programs that the Air Force Materials Laboratory supported and DARPA supported, we’d have more problems today in just windows to use with 10 kilowatt lasers, which is where they typically are used, or in entrance optics for experiments. The other big application, too, was the laser fusion program at Los Alamos, where they would have had no optics at all of it hadn’t been for the DARPA program. The other thing which came from this was the ability to forge infrared transparent materials, and it’s my understanding that they have found their way into FLIRS, as a cheap way to make focusing optics for FLIRS, and Honeywell —
— this is Forward Looking Infra-Red Sensors?
Forward Looking Infra-Red Devices, yes, FLIRS. And the capability that we developed in this at Honeywell to forge optical materials found its way into the FLIR business at the Army Night Vision Laboratory.
So it was really the Honeywell effort that produced them?
Yes, KBR, materials like that.
So even though the original application was high power laser windows for the programs that were being started in the early seventies by the Air Force and the Army and Navy?
Well, the AF Weapons Lab was to be the user of that. They were the principal agent to Dave Mann’s group in laser technology, and if a solid window had been used, it would have been used by the Air Force Weapons Laboratory.
Since you bring Dave Mann up again, it seems to me that they did not associate themselves very happily with his programs, after 1968, the Air Force Weapons Laboratory.
Maybe so, but I’m not very knowledgeable about those politics.
Well, you’re probably aware that Dave Mann was not the most popular —
— oh yes —
— STO director they ever had.
In fact, I could have joined that group. I was asked if I wanted to. And I said, I looked at who I’d be working for, and I said, no, I didn’t want to do that.
Well, some other things that came out of studies that were made under this program, Hughes did a study of what was called reaction atmosphere processing of alkali and alkaline earth halides. Did anything come out of that?
Oh yes. That was Rick Pastor’s work. Some early work on processing these alkali halides in a reaction atmosphere was done by Bill Frederick at the University of Washington, I think, some years before. Rick was a chemist and picked it up and proposed it to DARPA. The technique of crystal growth of alkali halides in a reactive atmosphere became a very important contribution, because it tended to leach out impurities which otherwise would get into those materials, and, for example, current efforts to develop infrared fibers of those materials utilizes RAP processed materials. Efforts are going on currently to produce photorefractive materials for use in non-linear optical applications that DARPA is funding and the community’s interested in was a process in a reactive atmosphere. So as a processing technique that was a very important one which Hughes and Rick Pastor had the sense to jump on, and get DARPA to support it. It was a very important program.
So this is a process innovation.
Oh yes. Yes.
You mentioned Battelle earlier. In 1975, you had Battelle, Pacific Labs I guess and NWC studying high power mirrors, to determine ways of measuring the scattering and absorption on the surfaces and improve their reflectance. I guess we said something about why Bennett would be selected for that purpose, because of his expertise in surface optics. Why was Battelle brought in?
They had developed and were operating a large laser up in Richland, Washington, and had developed various techniques for polishing surfaces which just looked like they had good performance. And the question was, why, what was going on?
These were ion-polishing techniques?
They may have been. That eludes me at the moment. But the idea of supporting them and NWC together was that NWC would do the characterization. I don’t think it was ion polishing, no, it wasn’t that. It was some other materials preparation, some form of pitch and other things which seemed to have some excellent performance, and anyhow, that’s what that was about and NWC was to do the characterization.
Was this, would you say, another piece of work you would single out as being particularly productive?
No, it was a medium kind of thing.
It didn’t produce any real innovations?
Not of remarkable, lasting import.
Another DARPA-MATS window program was one developed with Chemical Laser, and this was under J.A. Harrington at the University of Alabama in Huntsville, obviously associated with MIKOM. And it was apparently set up there so as to use the chemical laser that Tony Duncan and his MICOM people had developed at the propulsion lab. Did you start that up or was this a MICOM idea?
No, first of all Jim Harrington was at NRL. He was a member of that early group that was funded at NRL. He then left NRL and joined the staff at the University of Alabama, and set up working relationships using that kind of a laser at Huntsville. My interest in funding him was for any number of reasons. First, he was a very very sharp guy. He was aggressive and got work done. Secondly, the program had no good access to lasers at that wavelength, and calorimetry, which he was a proponent of, was a technique which we were developing in those days. Since he had access to that laser, we could actually evaluate some materials in the HF/DF regime, using calorimeters that he would build and take to the tests; so that was the reason for funding him.
Yes, I gather the minute he moved away, that funding dropped.
Under your successor, Captain?
Oh, Harry Winsor?
Winsor. UAH said, “He’s left but we have this real sharp guy who’s his assistant, give us some more money,” and they transferred it immediately out to Bennett at NWC, the same day they got the letter, they sent the money out west. You have a measurement program with the National Bureau of Standards to measure various properties of laser materials, and obviously in the standard scheme of things NBS does materials work and characterization work and that’s their job for the government. Perhaps the reason that they didn’t do all the work is at one point in ‘74 you reported, “Contrary to many basis NBS efforts, this program is off to a flying start. The progress, since the inception of the work in January, ‘74, has been excellent. At the recent IR Window Program committee meeting, every one of the six members was impressed with the quality of measurements NBS has produced.” So I gather that NBS was not a very impressive proposer but that they surprised you with what they could do, at least at first.
Right. At first I think the DOD had sponsored work on optical materials characterization with a few different people at NBS for a number of years, and it always seemed to kind of flounder and move slowly.
Was that because of the organization of the work there? Or that they didn’t have good people?
It’s mostly a combination of the organization, and the kind of people who work at NBS. Basically, they’re people who are dedicated to developing basically good measurement techniques, and those people, in this particular business, just were not aggressive. There certainly are excellent people at NBS who are more so, but the guys who were in the optical business at NBS were generally slow. I think what’s going on in this case was a slightly different group was used to measure some refractive indices of materials, and their temperature dependence, and that was judged to be critical. Those guys had the apparatus there and it seems to me they made some very nice measurements, in little over a six month period. And so they represented a different group. But the usual group at NBS is always just kind of slow about doing anything, never makes much progress very fast.
Now, here’s a project you mentioned earlier, where Raytheon and MIT got together to look at cadmium telluride, as an alternative material for IR windows. Did anything come particularly out of that?
We just learned the frustrating difficulty of making high transmission cadmium telluride. The Raytheon approach didn’t work particularly well. MIT set up to do CVD also of cadmium telluride and while it might have been somewhat better, it soon became clear that there were many other problems in cadmium telluride which were looming there, and there just wasn’t the money in the budget to take on yet another whole category of II-VI compounds of materials for this application, especially since the early results didn’t look good. So it kind of drew to a close very quickly.
Now, it’s interesting that it was one of the programs which Heilmeier, who became director of DARPA toward the end of your tenure - - it’s very fascinating because he’s the one who writes notes on these ARPA action plans, and one of the notes he wrote, June,’75, “Where are we headed in this laser window program? What are our goals? Where are we now? How much will it take to get there?” So naturally I go through the file to see, what is the answer to this? And I find a memo that answers specifically with regard to this, and promises another memo to answer on the big picture. Do you remember at all how you respond to this challenge to the program? I mean, I gather Heilmeier’s general strategy was to move things along at DARPA, and if he thought a program should go, it would go, so this many have represented — well, it’s the boss saying, justify what you’re doing.
Yes. I can vaguely remember that, and I suspect I wrote something else or if other opportunities came up to discuss it with him and lay out what the state of the art was and where we were going. The program continued; you know, after I left they got Captain Harry Wilson to come there and take over that activity, and activities continued in it. George didn’t kill it by any means, and it eventually died out only about two or three years ago.
It seems to begin to taper down in ‘77.
Yes. And taper down to one or several projects which continued for quite a while thereafter. It moved into the directions of techniques for making fibers which are highly transparent, I think. Harry started something like that. But the program, by the time George was writing that, was probably at that time three years old, and there were lots of things to be done, and I’m sure I defended it to him because the program continued for some years after that. Then DARPA began to move away from it.
Well you said at the first you were pessimistic. Were you more optimistic by ‘75 about getting the high power laser window? Did you think it could be done? I know there were certainly some fairly large programs going in that area by that time.
Yes. Well, we were highly pleased with the ability to get on top of and understand and beat back the limits to optical distortion in those materials. Whether or not they would ever be plugged into an airborne laser seemed to be beyond our capability to affect that, but from a point of view of materials development and producing materials for the laser community to use as optics in the infra-red, I think we were highly pleased with what had come of it. But you know whether or not it was going to fit into the engineering scenarios of a window for a large laser was problematic.
No, in addition to these individual programs, you had the coordinating IR laser window conferences, I guess, that you set up. wondered when I saw these, and I’ve only seen I think one of them, I’ve read some of them, and the same cast of characters who had contracts by and large are reporting.
Yes, that’s right.
I wondered though why it was deemed necessary to have these in addition to the Boulder Laser Damage Conferences, and I understand that the Boulder Laser Damage Conferences that I know have two components, one classified and one unclassified. There’s a whole series of classified reports come out of those too. So perhaps naively, then I look at what’s being done in laser damage, I see that there is a tremendous amount of literature being generated here; a lot of it is company reports on their latest laser glass or whatever. A lot of it is academic. A lot of it is military. And now you create yet another conference for people to go to and talk about these problems. Why did you feel that was necessary?
It was set up as a contractor program coordination vehicle primarily. It was a formal meeting held to get away from it all and have a small group of eight contractors or whatever, along with government laboratory people, get together two and a half days for information exchange. As the infra-red window program grew, and became what it became, it seemed rather nature to then blend it into the damage conference, and so that was done; in mid-seventies or whatever, the topics addressed in the infra-red window program moved over. They were somewhat different. The laser damage conferences always at the outset, looking at pulsed laser effects, and the IR laser window in the beginning was always CW effects, and it was a programmatic kind of a vehicle.
Now, laser damage conferences themselves tended to move from glass and ruby wavelengths, to carbon dioxide wavelengths, and to chemical wavelengths — as years went on you can see shifts, gradually from one to the other. Was the same thing happening in your program? You began to move with laser technology into these new wavelengths? Was there a real trend in this direction in the programs?
Yes, there was clearly a conscious trend moving in those directions. As laser technology spread, and the ability to generate high peak powers or even high average powers in the visible and the UV, we saw that the capability that was put together in this infra-red laser window program could be moved and slid sideways into these other spectral regions, and so it became a sort of an obvious evolution of the program.
To what extent did these efforts discrete? I mean, to what extent did you concentrate on one wavelength at a time, rather than a wide spectrum?
There were efforts to have it broad in the beginning, because if you used different lasers or different wavelength regions to characterize the transmission of the material, you had to learn more about it. Its performance, for example, at 3.8 microns versus 10.6 gave you insight into what was limiting their capabilities, and so there was always an interest in broad spectral characterizations of the materials, but it became obviously more important to do that as we saw the emphasis in laser technology moving to shorter wavelengths.
Steve Seitel at NWC caused a little bit of a stir a few years ago when he published a paper in which he said, “A lot of our large optics for laser applications are being regarded with one wavelength in mind, and we should really look, from a counter measures point of view, at what happens when they’re attacked by radiation on another wavelength.” And it seems obvious, but it appears that, at least he told me, that generated a lot of interest, that people from the counter-measures point of view found it novel, they hadn’t really thought much about it. That’s why I ask the question, how much this was built into the program from the start.
Well, I guess only in the way that I just gave it to you that is, as a characterization tool. It wasn’t much from the counter-measures point of view. It just, simply, you’d get a better handle on what causes —
But, ordinarily in these optical programs you would study a wide range of spectral responses.
Yes. That’s right.
The 1975 laser window conference led to a program that you launched to investigate the problems regarding the fabrication of durable reflective coatings and dielectric coatings for reflection-enhancement coatings of mirrors by Xonics. Was there any particular reason why?
That was a continuation of Marshal Spark’s work on looking at the limitations in those reflection enhancement coatings on metals, as well as on alkali halides, as well, and I guess, on visible wavelength materials.
So there’s no discontinuity here.
That’s right. It’s a continuation of Marshall Spark’s work. And the title reflected maybe a change in emphasis, of things to look at.
We did discuss the one process at Honeywell for making windows. Was there another? You cite two in your vita and I don’t know what that might have been. Maybe both processes were developed by Honeywell?
Well, I guess there was one. Harschaw has always had one, but they were a supplier of materials, and I’m not sure precisely what technique they used. The other one would have been at Raytheon, and it wasn’t a forging technique, it was in fact a casting technique, and was a process of being able to cast the materials, which looked attractive.
This was also the result of DARPA funding?
Who were the actors at Raytheon?
Rick Gentleman, Perry Miles, and people of that sort.
I’m sure these people published at the laser damage conferences.
Were there other things that came out of this program that we should talk about? These are the things I’ve been able to identify, but I’m sure I haven’t covered it entirely.
You’ve done well. I don’t think so. I think, in perspective, I think it was a program right for the times, as well as the Air Force’s zinc sulfide and zinc selenide ones. Even though it never was used in an airplane, it certainly has built the infra-red optics capability of the country.
How do you get the contractors to respond to a program which is largely 6-1? You want a broad-based effort and you want them to spend money to look into this. Were they willing to do this? Was this something they saw as potentially a profitable thing to do? Or was it something they went along with because you gave them the money and it didn’t hurt anything? You know, there’s the whole story in the American optical making of ND: glass, one of the real problems was platinum inclusions and their great reluctance to abandon their platinum principles as a technique for making glass, because the military market was just not large enough to justify making a big process innovation in their plants. Did you run into the same inertia say on the part of the contractors in these programs, or were you too much research oriented?
No, we didn’t run into that kind of inertia, because there basically wasn’t much of a capability at all, except at, perhaps, Harshaw who didn’t want government funding. Glass was used in many many applications, and they would try to just dope it with neodymium to make it useful for lasers. In the infra-red business, there were large boules of materials that were used as gamma-ray detectors, and then in very low power optics, but there was nothing like infra-red transparent optics, and so there wasn’t an analogous problem with respect to platinum.
Were they interested in developing these materials?
Yes. There were several commercial suppliers, who were always interested in and participated in the program; they always, however, had some reluctance to accept R and D money, because they didn’t want to compromise their future by having to pay government royalties or open up about their capabilities. But they were always right at the wings of the program. The larger companies, e.g. Honeywell, Hughes, have always been very enthused about DARPA 6-1 type support because it’s what they have a hard time justifying to their management, while as scientists they do want to do such studies. So usually there’s never any trouble getting the larger industrial research laboratories to take on that work.
The scientific group?
Yes, the scientific. And I’ve never detected any concern — let’s say, in fact, it was always the other way — even the heads of those laboratories always were enthused about 6-1 work and especially DARPA, because it perhaps meant bigger things in the offing from DARPA, but there was never any problem dealing with those organizations and getting them to take the money. It was always the other way around.
Did you have any pressure from the applications side, from the Air Force, from Avizonis and his group over in the AFWL laser Laboratory saying, “Why haven’t you guys got us a high power laser window material yet?”
No. The Air Force Weapons Lab guys saw it as a technology development and not plugging a hole in their program; they saw it as a technology development program, and they tracked it. They were kept abreast of it by AFCRL which was also doing it in part because they knew the Air Force needed such materials. But there wasn’t any direct heavy participation by the Air Force Weapons Laboratory. They had optics guys, who sort of knew what was going on, and they seemed to be content with that, and I never got approached by them saying, “Hey, you’re not going fast enough.”
So DARPA was really in many ways decoupled from these in-house development laboratories, it seems to me.
That they are a producer of research information just like other people are producers of research information, and apart from classification, which is not a problem with this particular program, usually, the relationship is just generated in the marketplace and if it’s useful, used, it’s not that you’re trying to feed them specific kinds of information.
That’s right. DARPA is a bit more fleet of foot. They have less commitments to institutions to continue to support them, and so, more flexibility, and the paperwork requirements at DARPA have always been significantly less than at service laboratories or wherever else they might support equivalent work, and so, their style is different. They can move in and out of a technical area very rapidly, or at least they could then.
I suppose one could say that apart from SDI, whatever it will be, or will become, one of the most significant spinoffs from the early DOD work has been in the laser fusion area, and I think we can move to talk a little bit about that. Although I understand the broad connections between DOD, DOE and the programs in laser fusion, the exact nature of those connections is a little obscure. First of all I guess we should find out why you went from DARPA to DOE. On the one hand, you’re leaving the Department of Defense which may or may not be a disadvantage. On the other, you are I guess assuming directorship of a rather important program in the Department of Energy. This implies on its face that they respect your DOD experience with laser glass materials and with lasers in general. How did that come about?
I had been at DARPA then about five years, and in early 1976, and I had always thought that what DARPA’s value is best served by good people coming there, developing and carrying out programs, and then leaving and let somebody else come in who has their own good ideas as to what ought to be pursued. I hate to see DARPA not have that kind of personnel turnover. So one of my own personal targets was that I thought about five years there would be as much as I should stay there. And the whole energy business came along about that time, the ‘73 oil embargo, they formed ERDA, and that just looked like an interesting new wave, and I’d been at DARPA five years and so, I didn’t want to leave the government, had too many years at stake in the government, and so I looked into the DOE. Anyway, your second comment was right. I didn’t know it at the time, but they were looking at “spinning off” the laser fusion program from the nuclear weapons program and creating a separate new division within the DOE to develop laser fusion for both military and civilian applications, and they wanted to give the program a lot more visibility than it had had up to that time, when it was buried under the nuclear weapons program. And so my resume, I’m sure, looked of interest to them because of my background in lasers as well as laser glass and materials, and so it all came together for those kinds of reasons.
Who was principally responsible for bringing you into DOE?
Well, Dodd Starbird was as head of the nuclear weapons program. These days it’s an assistant secretary.
He was Director of Military Applications?
Yes. He had held that position a long time ago and he went back to the Army and then got out, and was hired by the head of ERDA, from MIT, what’s his name, a professor, excellent buy. Anyway Starbird was brought in as the Assistant Secretary for Defense Programs, the civilian head of the nuclear weapons program which mostly involved the Division of Military Applications, and it was he who hired me there, and actually I had some other contacts in the DOE which kind of led to that. There was another somebody, person at Starbird’s level but who had civil energy technology going on under him, and I was quite interested in that, — he got together with Starbird and said, “Hey, this guy Stickley looks like he might be good for you in the laser fusion program.” I found out later that there’d been lots of discussions, that is lots of internal power politics, in ERDA about where to put this lasers fusion program. The people in the civil part of it wanted it there. Starbird on the other hand didn’t want to let go of it because he wanted it to remain a nuclear weapons-related program, there was lots and lots of maneuvering in ERDA before it finally wound up in Defense Programs and Starbird came out on top by winning all that.
As you say, the primary significance of this work had been in nuclear weapons simulation game, since I guess the early sixties when Livermore had kind of got interested in it and Ray Kidder was doing some work out there, and John Emmett went out. I really have yet to interview Keith Boyer so I’m not prepared to talk much about that work, but I’ve always wondered just how significant this was as a simulation technique. Was there a way to characterize that? When you came on board, did you feel it was a very important part of the nuclear weapons program in that respect?
It took me a while to learn all this. I’d never really been exposed to this technology in the Defense Department before. Obviously it had been kept under wraps. Its value to the nuclear weapons laboratories was that it was a way, under a Comprehensive Test Ban, for them to do something experimental in the way of diagnostics development, code development, and keeping their hands in some experimental aspects of nuclear explosions, even though they’re micro-explosions and not large ones. It was a program which gave continued vitality to the nuclear weapons laboratories, enabling these to continue to attract and have young bright people there. It was a simulator only in that sense. It was a tool more than a simulator of things. They haven’t been able to probably produce enough out of these micro-explosions to use it as a simulator per se, but it certainly is one which has a potential of giving them something in the laboratory to do which makes some sense, relevant to nuclear weapons design.
You suggest in a way that you know the recruitment or retention of personnel is, to some extent, affected by whatever glamour attaches to lasers and the use of lasers in experiments. From a phenomenological point of view, it occurs to me that, you know, it’s not really all that significant to use lasers to simulate these weapons in experiments.
Well, yes, you might not think so, but it really is, in the sense that there really isn’t any other way particularly of doing it. Now that’s really not what attracted all the young staff to Livermore. Clearly it was the energy applications, and the fact that they were committed to try to develop this technology as an energy producer. And that goal, that was the thing that brought them in in the early seventies, that started drawing people to Livermore and Los Alamos.
Well, in a sense they’re drawn, but then again in a sense, John Emmett goes there and creates a program, creates a program by recruiting the best people he knows how to recruit — Krupke.
— yes —
— from Hughes and the various other people — if you compare that to Los Alamos, Los Alamos, I don’t know how many people they recruited; they retrained a lot of their own people.
So there is a little difference between the two labs?
Oh yes, there’s enormous differences between the two laboratories.
It’s clear to me why lasers would be interesting. It’s clear to me why fusion applications for energy were interesting. I mean, that’s a pretty well known story. The weapons application, which is always alleged to be the most important part of laser fusion, even if it doesn’t look promising and it’s criticized by SCIENCE or somebody, that it’s not working compared to magnetic fusion, the argument has always been, there is always the weapons interest in laser fusion and that keeps it alive. Now, to your knowledge, is that true?
That’s true. I guess we’re talking about several levels of understanding here. At the lab level, what keeps it alive is good people doing good laser fusion work and it’s a good thing to have. So if you want to draw people there, lasers are to some extent glamorous, so this has been a recurring problem with the weapons labs. So at the lab level it makes sense. Now, at the DOE level however, we’re talking about something a little different. DOE personnel, the people at the Washington level, are not merely representative of the laboratories. They’re also representative of the Department of Energy, which relies it’s true on its laboratories.
But there’s something you say which isn’t quite right. In the Division of Military Applications and in the Office of Laser Fusion, they are pretty much representative of the laboratories.
Because that’s the only action you’ve got going?
Because that’s all you’ve got going, and basically those laboratories tend to help staff the government DOE operation. They provide the staff for the DOE in many instances.
Yes, but you were a novelty in this respect. You are not, as are many people in DOE, coming from the strong laboratory system. You’re coming from a department which has a fairly weak laboratory system by comparison, has spent most of its research out of house.
You’re coming into a program where the most significant milestone that has been announced in 1976 was not made by an in-house laboratory, but by KMS Fusion in 1974. They are the first to get, you know — they claim to be the first to get successful pellets, to get thermonuclear neutrons out of a laser pellet. So in a sense, what’s your perspective? You come in you say, sure the labs want to help each other, they want to have something interesting to do, but - - and certainly Starbird wants to keep the labs together because that’s what DOE is all about. What is your perception? Do you feel that the main justification for having a laser fusion program is to keep these guys going? Or do you have others?
No, when I went there, the justification for it, as far as I could see, was basically the world needs fusion as a long term energy source and damn it, here’s a totally different approach from magnetic confinement, and secondly, here’s this fascinating result presented by Emmett and Nuckolls at ERDA headquarters to me and to people above me, within a month after I got there, of some very exciting results from classified targets.
Can you say what they were?
Yes, because it’s been declassified, since then. It’s basically a little radiation case, where you have a beam entering a very small box, through a hole, the beam reacts with the inner surface of that box and creates X-rays. And also in this box, in the right position is a little pellet which will be an absorber of these X-rays, and in fact, when they absorb it, if it’s done properly, the X-ray penetration process would wind up compressing this little pellet. So it was a way of sort of taking a laser beam which might not be very good and smoothing it in a way and converting its wavelength to one in which the absorption would occur in some sense in a better way at the surface, and compress the pellet. First of all, I guess, when I came there, somebody a lot higher than my pay grade had decided that laser fusion was a good idea, and I didn’t much question that. The head of ERDA had decided that. I found a program with military connections which I later found out about, but the predominant wave of enthusiasm for it was as a potential interesting long term fusion approach. And that was the thing that I found going on, and that kind of enthusiasm amongst the people in the program for it was as an energy source.
John Emmett was very enthusiastic, and Nuckolls. What about Boyer? Was he still there at Los Alamos?
Yes, Perkins came on within a year or so after. I got to the DOE, found a great contrast between Livermore and Los Alamos, and that Los Alamos needed something to help stir them along, so they put in Roger Perkins as the head of the program. There was certainly enthusiasm at Los Alamos, but the character of that laboratory was low key and they couldn’t match the flashy style of Livermore. Basically they didn’t radiate as much enthusiasm as Livermore did. They also retrained their older staff and did not bring in a significant number of young laser experts. Their focus in those days was on, how is this laser energy going to be best generated in the long term, and so they saw carbon dioxide laser radiation as being the way to do it. I was amazed by that when I first went to ERDA. But Los Alamos was enthused about their program too, and there was obviously the usual competition. In fact, it was even more competitive between those two groups in the laser fusion program than it was in the nuclear weapons program. You know, they represented a bunch of younger people with this competitive instinct, and the competition was, in a sense, at its worst in the laser fusion program.
It occurred to me that given your knowledge of glass laser systems, it’s astounding that you should think that a laser fusion device based on glass should work, because of the very significant thermal distortion problem that you have to overcome.
There thermal distortion problems are not at all bad on a one pulse basis, a single shot basis. I never saw it as high rep rate, many-pulse-per-second technology.
Well, would it work for laser fusion, as a production?
(crosstalk) Oh, sure — oh, as a production? No.
Just to get your break-even.
Yes. The program desperately needed some way to get enough high quality single pulse energy just simply to produce enough energy to work with to make a sizable mini-nuclear explosion so you could begin to tune it a bit.
But the arguments from Los Alamos, which I know you read a lot of, because I read a lot of it directed your way, was look, Nd: glass is an obsolete technology even if it works, in the long term it’s gas, carbon dioxide or a system like that with new lasers, so why not put money into these new systems rather than building a gigantic NOVA that will be obsolete once it has done its job, which is to achieve scientific break-even? Now what you say, you were interested in the symbol, the symbol being scientific break-even?
I was interested in energy gain, which was first promised by Emmett.
OK, you wanted an energy gain of 20 or whatever.
And you say, OK, I can get this from NOVA pretty sure and I can’t get it from NTARES quite as sure, and if I listen to Emmett, and I’m not going to get it with NTARES at all, but I am going to get it from NOVA. The arguments go with something like this, at least in the correspondence. And also what seems to weigh large in testimony in the correspondence is this desire to reach gain, by the time that the magnetic fusion reactors would do it. Whether or not you admitted to Congress, there was a real sense of competition between the programs.
And if laser confinement fusion or inertial confinement fusion, is to survive, it has to reach break-even at about the same time.
That’s right, sure, it can’t afford to be the diesel engine in the business.
OK, so that’s why I pick up on the symbolic nature of early NOVA. Now, I don’t know if NOVA has yet achieved break-even. It’s supposed to do it sometime this year. So in essence there wasn’t any real argument, there’s just two levels of understanding. Los Alamos says in the long term you need a better laser. You didn’t disagree with that.
You’re interested though in the medium term demonstration of scientific break-even, and that was worth what it would cost to build NOVA.
It wasn’t that I argued that a gas wasn’t the best kind of medium. That seemed to have lots of things going for it. The problem was, it was also ten times longer wavelength radiation.
What was that problem?
The problem basically is that you’ve got an oscillating electric field which at 10 microns is ten times slower than it is at 1 micron, and the process is one of being able to accelerate electrons to make them hotter. You can do that much more readily with 10 micron radiation than at 1 micron radiation, and it has to do with the fact that the field is slower, which gives you more time to build up energetic electrons. Those energetic electrons can penetrate that fuel. They get to the energy where they can go right through the fuel capsule, and heat it, and that prevents you from compressing it with the X-rays you generate from this pellet. So it had that sort of intrinsic nature of matter going against it. So it looked to me that there was clearly a disadvantage to CO2 laser radiation and obviously it would be a lot better to have something ten times as short a wavelength.
Now, later there are reports that these wavelength effects had not been as bad as they had been anticipated to be. Is that true?
I left the program in 1979, and I haven’t had — let’s say, aside from a discussion with John Nuckolls in the spring of 1984, that is, I’ve had no communication with that community since leaving it.
Well, but for example Perkins, in the FY ‘79 testimony, said the wavelength effects were not as bad as predicted.
That’s Perkins. Anybody giving testimony is going to try to put it in the best perspective, and we encouraged them to do that. That was certainly true. Well, you know, all the testimony tended, as it should, to reflect views which would probably be helpful to get the budget requests supported. But basically, in 1979 things didn’t look all that great for anybody. Things weren’t coming out nearly as rosy as we had hoped, even for 1 micron radiation. In fact, the great disappointment I had with that program was that the early results by Nuckolls and Emmett were improperly diagnosed, and there were hot electrons there that they didn’t know were there, and we didn’t discover that until probably two years later, then RGUS got going and better experiments were done. But what I was leading up to was, we felt it necessary that the Congress have a choice. We had to compete with magnetic fusion, and it didn’t make sense to manage it so as to not make it competitive and so forth. You’d be obviously a candidate for being eliminated. Since we didn’t want to do that, you had to posture the program in some way to at least try to make it compete with magnetic fusion. So we had to make some decisions, and the decisions basically, as far as I was concerned, were to go with a NOVA design, because it was a shorter wavelength, it was the better group, Livermore, and if it wasn’t the ultimate solution, so far as I was concerned, that was something against it, but in fact, that’s what most people didn’t understand. What the fusion program needed was some results. It couldn’t afford to wait to build the ultimate laser to test pellets. You had to get a laser working with Fuel-pellet interactions, to be able to produce the neutrons you were looking for, so you could begin to table that and work that design. And so it just seemed to me by far the quickest way was to go with the large glass systems for those two major reasons, in an effort to get productive fusion, productive neutron development, from these pellets as soon as possible.
In ‘77, when you were testifying on the FY ‘78 budget, you said it was your view that the glass laser fusion technology was the lowest risk, nearest to being completed, and would give us the surest route to demonstrating high energy yield. That’s what you just said. You admitted however that glass laser systems as now designed and built are not efficient enough or rapid firing enough for fusion powered reactors. Sufficient advances of major laser technology would be required in order to operate glass lasers with the efficiency required for fusion power applications. Now, this seems to suggest to me that you believed that, since you were familiar with 15 years of trying?
It was partially a matter of giving John Emmett the benefit of his faith in the technology.
He’s a true believer He thinks you can get a glass fusion reactor to produce energy.
Yes. I don’t know what John thinks now. I know in those days, there were thoughts about slab lasers and designing these large systems to conduct the heat out, sort of in a direction nearly parallel to the beam direction. Also they were looking at the use of arrays of light-emitting diodes or semiconductor lasers to pump these systems. They would be far closer to the lasing wavelength, and therefore would deposit much less energy, causing less heat to be generated and leading to a more efficient laser. And there was Emmett’s general confidence and views as to what might ultimately be possible, so I saw no sense in cutting that off. But the outstanding reason for doing it was that it was the lowest risk way to try to get laser fusion to work. I was far more worried about achieving that than what the ultimate laser might be for driving a fusion reactor.
That’s a significant characterization because I notice you got into a number of conflicts with the Los Alamos people at those hearings.
Yes, in fact it was interesting. When I first got there, I discovered that they were serious about a big CO2 laser for fusion. But all the stimulated scattering processes and just coupling laser radiation into surfaces through the plasma is going to be worse, and so, I thought what I’m going to do is have a summer study so I can understand why we’re pursuing CO2 lasers in the first place. So I went about doing that, and then it didn’t take much more than a day before Harold Agnew found out I was going to do that, and he called Starbird and Ed Giller and I got the message from Giller that I should probably not do that.
That reminds me of the joke about Ernest Lawrence, when the AEC was set up. It went around the Rad Lab that they even had the right to discharge laboratory directors, and everybody said, “Well, look, what about Ernest Lawrence? Can they do that here? They said, “No, in this case, the laboratory director discharges the AEC.” And to a large extent, at that time that was true. So it’s interesting that this still happens on a somewhat smaller scale at this point.
I happen to have a document, which I found at Los Alamos, in which you admit that one of the problems that you run into, in the face of the Carter cutback in funding for programs, was that you had a grudging unwillingness to back away from formulating an aggressive program because of your enthusiasm and optimism for it, and now you were being cut back and you had to make decisions. You couldn’t fund all the programs at the level that had been projected. You were on the verge of cutting back Los Alamos to just keeping the lights on and sweeping the floors. And at this point you were trying to get Perkins Emmett and Beckner to agree on a long term strategy which would involve construction of a small NOVA, smaller than what had been styled NOVA 1. That was in the same time frame as the IFTR, which of course made Los Alamos and Sandia very unhappy at this point. You’ve talked about why you wanted to do that from a political point of view, but you haven’t talked about the first part of the statement, which is that you felt that you had been too aggressive in formulating too broad a program.
I had wanted to move out rapidly. It was the beginning of the sort of discouragement that the country, certainly as a government person like myself, found from OMB and from Congress in supporting energy research. We all had seen the kinds of studies that had gone on about the shortage of oil, what was going to be needed in the way of energy, and so my own judgment was, you know, we’re going to have a go at making this fusion process work, and we’re going to ask for the support to do it. But two years more of heavy funding was needed to really finish these facilities and get on with it. So the discouragement was real since this support wasn’t there. People were asleep in budget meetings at DOE. You’d go to OMB and they aren’t all that enthused about fusion. And there was no reason on a technical basis why they should not have been enthused about it at the time. That would come later. But it was the beginning of disenchantment, more or less, the turndown of the energy development cycle in the country. And I had, I guess you could say, not foreseen that, and had begun to try to commit to getting these big facilities finished at all the laboratories, and struggle as I might in dealing with the budgeters in DOE and in the OMB, and the Congress, it just didn’t seem like it was going to work. So the overly aggressiveness was, on my part as program director, to be willing to go out and find the money to do all those things, and I wasn’t able to do it.
OK, now if you had to make your bet, you wanted to be NOVA.
There were some estimates being exchanged about the possibility of the large carbon dioxide laser reaching scientific break-even, Los Alamos’s figures are very optimistic, Emmett’s figures tended to be pessimistic. As I recall, Los Alamos had some very strong arguments against that investment, and pointed out that there was a certain inconsistency in estimates at one time as opposed to another, as to the potential of NOVA and as to the potential of NTARES. Whatever their eight-beam carbon dioxide —
It was called HELIOS, I think, and then ANTARES was the big 100 kilojoule laser.
So, what I’m saying here, OK, are you liking NOVA because it’s the group? Are you liking NOVA because you’re a glass laser man? You know, there are carbon dioxide laser men, there are chemical laser men and there are glass laser men. What is it that appeals to you? Is it just this energy gain in the short time?
It’s the same reasons as before. I just felt that there was by far the greatest chance of doing it with 1 micron radiation. And that the lowest risk, in the sense, that the group, in my view, with the highest performance was still Livermore, and that the way to go to try to get the early fusion results, was to continue in that direction. And so it was both, to my view, the relative favorableness of the wavelength, and the quality of the group.
Well, can you put into this picture the new lasers program that you launched? You talked about it in a PHYSICS TODAY article. Los Alamos began a new lasers program and abandoned it in a couple of years, partly due to lack of funding. And all these were candidates for future fusion drivers. How serious was this effort, in terms of your expectations for a reasonable fusion drive?
Yes, the program needed to have something of that sort coming along. When you’re running a big program of that sort, you can’t put all your eggs in the near term basket because the time necessary to kind of catch up, if you don’t do that, is a huge penalty, so you’ve got to always be paying a bit for the future, and that’s what the effort in new lasers represented. The DOD was certainly marching ahead with funding work, at various organizations, on excimer systems, and it just certainly seemed like the Department of Energy and the Laser Fusion Office needed to have something going on where people were, you know, keeping their hands dirty in developing scalable shorter wavelength lasers. So it was, if you don’t have such lasers coming along, and we should be successful in getting some very significant fusion results from NOVA, you don’t want to be caught in the situation of having to stop and start from scratch to develop a fusion laser. So it represented an effort within the DOE to get on with developing what looked to be the next generation of laser drivers, which would be a gas system, and which probably would work in the visible, or should work in the visible, because of our conviction that if you’re given a choice of an infra-red photon and a visible photon, life is going to be better if you go to shorter wavelengths.
Now, in this context, though, wasn’t most of this abandoned in the 1979 funding cutbacks?
My memory is a bit foggy on that.
I know that, for example, Los Alamos pretty well cut theirs off.
Yes. And it probably represented, at Los Alamos, a concern that they had to put their money into keeping their mainline activity alive, and so I guess I’ve forgotten any rationale for the detailed manipulations.
I just wondered where it fitted into the larger picture. It seemed to me basically the story you’ve got is of competition between two labs for funding in this area, and that for the reasons you talked about you tended to fall in with the Livermore people, and of course, as is shown, the Livermore people are now completing the program that was begun then, with the big NOVA, whether they get break-even this year or not.
Well, unfortunately, it’s always been a high risk program, and it could have been done, as I said, with the exception of the one major thing which wasn’t done properly, and God knows for what reason, but the two Johns didn’t do a very good job in the diagnosis of the first classified experiment results. So I always have felt sort of misled by their improper characterization of the performance of their classified pellets.
The classified pellets idea is just simply the transfer of some laser and X-ray energy, is that the basic concept which was classified?
It’s basically how a nuclear weapon works. You set off a fission bomb at one focus and you produce X-rays from it and that ignites the fusion reaction.
As Progressive Magazine has told us.
As Progressive has told you. And that’s unclassified. The laser fusion ideas are similar.
Well, I guess I’d like you to make whatever statement you could about the more general issue of the technology transfer from the DOD programs to the DOE programs. I know that’s not a simple thing to characterize, and a lot of personnel moved from one area to the other area, as you yourself did. One could argue that Los Alamos and AVCO developed ideas about carbon dioxide lasers at about the same time, but certainly the glass laser business is largely a DOD baby which was moved with John Emmett to Livermore, when he went there, and DOD lost interest in the large scale glass lasers at the time DOE picked it up.
Large scale glass lasers, right.
It seems the Soviet Union in this period did not lose interest in large scale glass lasers for these applications, so they had developed things like athermalized glasses, which made glass lasers look more interesting not only for - -
I think the athermalized glass is something that the US could have done. I think the US can move its programs much more flexibly and quickly, and at its budget level for this, certainly chose to support gas laser technology. The Soviet Union, as you know, once something gets rolling it’s quite ponderous, and it can keep on going, and the glass laser enthusiasts there, I’m sure, keep the materials development going. Largely that same interest still exists in the DOE laboratories. The materials work, for example, that’s going on out of Germantown, Maryland, in the Department of Energy, is toward developing improved optical materials. So in a small way that interest is still there in energy, in DOE. With respect to DOD-DOE linkages, it’s clear that the biggest thing I see was the training of personnel in the defense laboratories and contractor operations and their subsequent transfer to the DOE labs. The growth in popularity of laser fusion soon after the energy crisis led to their attracting people there. The glass laser technology, which was developed early on at NRL and other places, is clearly an important thing too. At Los Alamos, on the other hand, the Congress killed the ROVER program and basically their source of people was pretty much retraining people from that program. I always felt that while that was certainly the humane thing to do, they should nevertheless have still brought in a few key people from outside of that community who knew laser technology. They should have hired somebody away from Livermore, to help themselves. They always were a little behind in the laser technology area. So those are some of the differences in the laboratories. But in terms of technology transfer, I tried to get more aerospace technology into the program. A thing you haven’t touched on in this line of questions is the program that I started to get contractors into the business of making the pellets. Making these pellets was a very demanding materials science program which really hasn’t been conquered, but it seemed to me that, with the integrated circuit capabilities of the US industry, and with the aerospace capabilities in laser optics, that we should perhaps try to marry these with the laser fusion program, in trying to make and mass produce the kind of pellet that we used. I also felt that there were other legitimate capabilities which DOD contractors had which could help the laser fusion program, in the classified area, and so, one of the most different things I did was to initiate a program in which half a dozen DOD contractors became contractors under the laser fusion program, with classified knowledge provided as they needed it, about the classified parts of the fusion program, so they could help the DOE community make targets. So this is a case where I decided tried to make some positive connections whereby a DOD capability begins feeding into the longer term needs of the Department of Energy. Anyway, Starbird left and then the replacement to Starbird asked me to leave, which clearly helped to kill those programs. They were viewed in various ways by the laboratories. The laboratories were always concerned about their future, and I think they’ve always viewed it as being that. So those programs, while being innovative in an attempt to couple defense contractor capability to the DOE, just died away. I guess the only one remaining was Westinghouse working for Livermore in the area of cavity reactor design. Other participants were organizations like Physics International with good electron beam capability; and KMS Fusion with their efforts to do classified target work. In fact, we tried to set up a KMS fusion pellet capability at Sandia in Albuquerque to help the Sandia guys with their pellet needs, but I think all of that died too.
Was KMS still working on DOE contracts?
Oh yes. But they had never been given any information about classified pellets up until the time I arranged for them to do so. They had their own ideas about classified pellets, which they had come upon by whatever techniques. But there was never any information exchange between KMS and the laboratories. There was never any funding by the DOE given to KMS to do classified pellet work. But it was felt that, before I got there, that there had to be some way. They had ideas about pellets which it turned out were classified, and the way to cope with that was to let them do work with their own money but insist that they keep the stuff secure and locked up and there was never communications in a formal way between KMS Fusion and Livermore and Los Alamos.
What was the reason for this pellet work being classified?
Oh, because it’s a model of a thermonuclear reaction. It’s a scale model of a bomb.
I see, so once this Progressive information was leaked, it was felt it was declassifiable?
Well, it was felt that, it was leaked. It was the judgment that enough was out that they couldn’t go on denying it. But they certainly drew the line at any information beyond that, about details of this whole process and the technology that goes into it. They drew the line there. So that they admit now to the fact that it’s a radiation case concept — they admit that that’s how it works. But that’s all they’re saying. But up until this classified program which I started, there hadn’t been any funded efforts by KMS, to work on classified pellets. They had a contract where they could do what they wanted. But they had to keep it there. There wasn’t any information exchange between groups.
So here, classification is a barrier to progress.
Yes. And also there are times when classification is used to protect a position in a technology or a science. I’m sure it’s a bit of that too. It’s both.
So DOE laboratories are becoming like some industrial laboratories.
Well, look, it’s important that that information not get out, but it’s also ridiculous to think that you can’t trust other US citizens with TS DOD clearances to not spread such information. It’s ridiculous to think that there isn’t a lot of help which they could get in the pellet fabrication business from US industry. All I can say is I can certainly tell you that the DOD runs classified programs all the time involving these same groups, and to the benefit of everybody, and it’s still my conviction that the DOE could do the same, without any further release or irresponsible spreading of this kind of information.
I think there are some interesting contrasts between DOD and DOE. I wonder if you would care to extend it to the nature of the laboratories. You were head of a group in one laboratory, and you certainly had a lot to do with DOD laboratories.
There’s very little that you can compare between them. The Defense Department laboratories are far less political, on a national scale, than the Department of Energy laboratories. Politics in a technology sense in the Department of Defense is minuscule compared to the Department of Energy. For somebody like myself, going from the DOD into the DOE, I was a real neophyte in all of this, and really didn’t have an appreciation of the political morass I was getting myself into. I saw it, you know, very very much in a naive way as just being a technical issue. However, basically under Starbird, he was a good enough guy that he saw it that way too and was willing, to some extent, to make sure it was run technically, as best he could. But he retired or left.
Was Starbird also in a position where if he wanted to protect you from political pressures, he could to a large extent?
He must know where more bodies are buried than any other single individual.
Oh, absolutely. But you know, when Harold Agnew called him up and said, “What’s this Stickley going to do running a conference looking into my laser?” I’m sure at that time he decided, well, maybe we should back off, if Harold feels that strongly about it, we should back away. The DOE laboratories are extremely important to this country’s future. They are well positioned. But in areas where they overlap into the civilian R & D sector, in terms of their capabilities and what they’re trying to do, they don’t do that very well. I saw it in this laser fusion business.
Well, don’t you think that the DOE people tend to think of themselves as a cut above industrial researchers, and certainly more than a cut above most military research people?
Their laboratories are set up to give the illusion of working in an academic environment, free from government pressures, on research that is glamorous. Freeman Dyson said in his book on Weapons and Hope I don’t know if you’ve had a chance to look at that — that what really took the heat out of nuclear proliferation was when THE PROGRESSIVE published the H-bomb stuff, and everybody realized, it’s no longer very interesting, it’s no longer very glamorous. Most physicists are not interested in working on nuclear weapons any more. And there’s a lot to do this. There’s a lot of glamour in being at Los Alamos or Livermore because this is the only place you can work on this kind of thing. One thing that strikes me when I talk to many people in the laboratories is the Teller phenomenon. He’s a symbol of what the glamour of the whole business is. But I don’t think the military labs, even though the attempt was made in the early sixties to get good people in, they had the opportunity to do with lasers, in a sense, what had been done with nuclear weapons, except that they couldn’t hold it all in, they couldn’t develop a lot of the technology. There’s been talk over the years about lasers are glamorous and lasers are the answer to nuclear weapons or the ABM to them, and to some extent, the fact that such talk exists reflects the fact that there’s something to it, a little bit of feeling that this is the new glamour technology that takes the place of nuclear weapons.
It occurs to me that the military laboratories in the sixties were in a position where they were trying to become strong or stronger as a result of the Bell Report and the Systems Command in the Air Force.
And that the lasers provided a seed, if you will, for a crystallization of a new research capability. Places like AFWL got a lot stronger because of lasers.
But for the most part NRL didn’t pick up on it till Sooy came, in a really big way. I mean, Sooy really galvanized that place in a way it had not been before. Air Force Cambridge Research Lab has always been sort of a halfway house between the academic and industrial communities and the military, anyway, so it wasn’t looking to build the capability but to serve that clientele.
— right —
— and to do basic research. And now, on the one hand, you have the failure of all the early, test-bed programs in defense — in the sense that all is in mothballs, the Coastal Crusader never sailed, and the MTU is split up between NASA, the Marines, and will never shoot down a helicopter.
Well, let me go back and touch on the difference between the laboratory structures. Fortunately the nuclear weapons laboratories are not civil servants, they’re not really truly government laboratories.
By design. And somehow, the DOD laboratories should have been structured that way also, because as good as AFCRL was when I went there in 1958, and as fast on its feet as it was, it’s continued — it and all the laboratories have continued to lose their capability, with the growth of, and the strictures put on it through civil service, the GAO, inspector generals and all the other bureaucracy that has grown in the DOD. And so that’s the thing that’s really badly affected Defense Department laboratories, at least from my perspective, as I’ve seen them. I think the DOE laboratories are far better these days because they are not civil service laboratories. With respect to SDI, I don’t know. I guess I see myself working in it, BDM working in it; whether it’s going to work, I don’t know. I would view it as a very high risk enterprise, obviously. Of maybe not ground-based ASATS, you know, that’s a thing which might in fact come. After all, there are simple ways in space for killing satellites. And so my own feeling is that, in an R and D sense, let’s work on it, because if there are some real breakthroughs, and it would really have to be that, it would be important. I think the Fletcher Committee which met somewhere a year ago, from all I’ve been able to gather in my discussions with the people who were on it, felt that that committee, after the first few weeks, the forty guys, 20 people in it, functioned about as reasonably as you could expect with an operation of that sort, and came up with a fairly balanced point of view, and the point of view was that this looks worth a national effort to go out and try to do. And I think, given the character and nature of most of the people I know on it, I wouldn’t question that. I haven’t had the opportunity to get in and debate all those guys. But, on balance, they probably have the right point of view, so I would support what they recommended. Unfortunately, I see the SDI is not doing what it was recommended for.
No. It was unclear the last time I talked to anybody about what the SDI was doing. On this trip, I’ve seen some evidence that motion is taking place, but apparently they’ve just got their leadership structure in place.
Well, the Fletcher Committee pointed out that it was necessary early on to try to look at what maximum practical hardness you can develop against each of these beam weapons systems, and get that data. That missing data has the highest significance, and the program ought to be structured to try to develop that as soon as possible.
That’s what you’re working on here?
It’s actually just hardening, how well might you be able to harden against, in this case, CWDF lasers. And that was the highest priority recommendation of the Fletcher Committee, and I see that the SDIO is not grabbing that and organizing itself around trying to address that question first.
Did you come here with the idea in mind or working on laser systems?
Why did you come to BDM?
Oh, because I didn’t want to move out of Washington, and yet I was going to leave the government, so I looked around for something which was in the Washington area, which would be attractive and challenging. There was nothing in any of these areas when I came here. Basically, I didn’t want to move to Detroit or whatever, and my children were sort of adjusted to schools here, one was just in the last year of high school and there are two others coming along. We wanted to stay in Washington.
Well, my parents, I was born in Washington. I’m a native, one of the rare people who’s a native Washingtonian, even though I didn’t live here for 20 years. In the late fifties I was in high school and college, and the sixties I spent in Boston.
Well, is there anything else that it occurs to you that we haven’t covered?
There is another thing that I could touch on. And that’s the X-ray laser program.
Yes. I guess that reminds me of yet one other thing, which is the free electron laser. Regarding the free electron laser, just before I was leaving DARPA, the last funding action I made there was to arrange for Madey of Stanford to get some small amount of money, 50 or 75 K was all I could scrape up, to help keep his activity alive at Stanford. And I was always struck by that, struck then and now am, that Madey could not get any money from STO. Peter Clark wouldn’t support that. And the Air Force had pulled out — the Air Force Office of Scientific Research had ceased funding it, sort of within months of when they got the interesting result, and Madey went to STO, which was the Directed Energy Office I guess. He came to me, and so I scraped up what money I could and funded him to keep him alive until some next bit of funding came, I guess I’m not quite sure from whom, but I was always, you know, in retrospect bothered by the near-termness of the DARPA Directed Energy Office’s view about such things.
That was in the era of course when SLTD was going on, and they were looking for short range applications at that point.
But when Heilmeier came in, he sort of looked more into the space business.
Yes, he first helped try to refocus all that towards space. But I felt it was ridiculous to see this fledgling significantly supported activity at Stanford just simply die for the lack of a small amount of money to keep it alive. Anyway, so that money sort of provided the last amount to Madey before he got his FEL working. In fact, the first money I’m sure in free electron lasers at DARPA or SDIO came from my former office, the Materials Sciences Office at DARPA. The second thing was X-ray lasers. And that’s an area which DARPA I thought would pursue: that’s an interesting high risk/payoff technology that the US ought to be doing something in. And Steve LuKasik was the director of DARPA then, and I had talks about it with Peter Clark, who’s a good friend too. Peter said no, there was no way they were going to do such a thing, and I thought, gee, the US ought to be able to scrape up some money somewhere to do some long lead time looking at how to get into the X-ray regime. So I started an X-ray laser program which involved University of Rochester, Livermore, NRL and maybe two others, Battelle.
I saw reference to an NRL program, an ARPA/NRL X-ray Laser program.
Yes. Anyway we got it going and it was funded for a year or so. I guess I started it about a year before I left, maybe a year and a half, maybe by ‘74. Then I left, and the George Heilmeier killed it, after I left. But anyway, one of the interesting things I funded was a joint effort proposed by Livermore to develop the code, to be able to predict basically the code descriptions of that kind of a laser. George Chapline and Lowell Wood. And they wanted 250 K, which was the biggest chunk of money that I gave out in that program. They wanted $250 K, and they were going to put $250 K of Livermore money into it and really try to make some progress in it, using LASWEY codes. And, a year after that or during the first year I found out, or after the first year, I found out to my disgust that they had not matched funds with DARPA the way they had said that they would, and that they really just took the DARPA money and they didn’t follow through on that. And so I was very chagrined, because it would have been probably the most important part of the program, in a calculational sense, because that was necessary. Rochester and NRL had experimental capabilities too, but the Livermore one was going to be very important. I carried that grudge with me when I went to the Department of energy, aggravated that they would have done that. And so I let it be known when I got there that that had happened. That was interesting.
Was there any response?
No, embarrassed silence. They kind of ducked and just tried to get out of the way. There wasn’t much they could do. But anyway, you know, X-ray lasers are that — I can’t say much about what’s going on in the laser business, but the US at least had beginnings with that program.
It’s interesting, about the NRL program, there was a meeting I guess in ‘74, ‘75, at NRL about this group and the potentials for X-ray laser, and then this program got started later and there didn’t seem to be any clear connections. It will probably turn up in some of the files I haven’t looked at yet, that being a little later on. You wouldn’t remember the order number?
No. But it would have been somewhere around ‘74.
So far I’ve been so busy with what I’ve found that I haven’t worried too much about what I’ve missed. Well, that’s very good.
"time variation of axial frequencies in ruby lasers," in W.S.C. Chang, Lasers and Applications (Columbia: Ohio State University Press, 1963), 235-250.
Report on Research at AFCRL, July 1962-July 1963 AFCRL 64-25 (1964), 227-8.
"Photographic Studies of Mode and Polarization Phenomena in Ruby Lasers," Journal of the SMPTE 72 (July 1973), 534-536 (with D.W. Lipke and T.J. Healey).
"Observation of Beats Between Transverse Modes in Ruby Lasers," Proc, IEEE 51 (May, 1963), 848-849.; "A study of Transverse Modes of Ruby Lasers Using Beat-Frequency Detection and Fast Photography," Applied Optics 3:8 (Aug. 1964) 967-979.
"Optical Quality and Radiation Patterns of Ruby Lasers," Applied Optics 2:8 (August, 1963), 855-860.
"Laser Brightness Gain and Mode Control by Compensation for Therman Distortion," IEEE J. Quantum Elec. QE-2 (Sept. L966), 511-518.
"Color Centers and Ruby-Laser Output-Energy Degradation," J. Applied Physics 40:4 (15 March 1969), 1792-1802.
"Applications of Lasers," AFCRL-64-914, November 1964.