Oral History Transcript — Mr. Gordon Gould
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Interview with Mr. Gordon Gould
Gordon Gould; October 23, 1983
ABSTRACT: Studied at Union College, worked at Westinghouse. Initial graduate work at Yale University, 194l-1943, with concentration on optical spectroscopy. Trained personnel in vacuum technology for Manhattan Project. Additional graduate study under Polykarp Kusch at Columbia University; at I. I. Rabi's suggestion, applied optical pumping in his thesis work. Suggested optical pumping of maser. Remarks on maser's commercial potential and potential of the laser. Discussion of his attitude vis-a-vis Charles Townes and Arthur Schawlow, ca. 1957. Recruitment to Technical Research Group, Inc. and work on laser, ca. 1958. Almost entirely concerned with Gould's activities from 1958-1967, while he was at TRG Inc. Reception of his laser idea by TRG staff, job activities during the years when his lack of clearance prevented him from concentrating on lasers; some of the laser projects he undertook once TRG's laser contract was declassified.
TranscriptSession I | Session II
Gould:All right, you have given me a list of questions to stimulate me, and they certainly have stimulated me to think about things that I haven’t thought about for a long time in some cases. And since my answers will tend to be in response to these questions, maybe I’ll read each one and then talk about it. I should note that the questions raised here are not necessarily in any time sequence. They tend to skip around among various areas.
Bromberg:You might want to even reorganize it.
Gould:Well, I can’t really do that offhand. Now, question 1, is, “In your first interview, we went as far as your disclosure of your laser ideas to TRG’s management. Could you please tell us now about your discussions of how to implement your ideas? What were the decision-making processes that finally led to TRG’s proposing laser work to the then newly founded DOD agency ARPA, Advanced Research Projects Agency?” Now, I should recollect that when I came to TRG, I didn’t immediately reveal my ideas about the laser, because I wanted to make exception of those ideas, and also a number of other inventions I had in mind, from the usual patent agreement that one signs on joining a company. — and the president of the company, Dr. Lawrence Goldmuntz said, “All right, I’m perfectly willing to make an exception of these ideas. Just write them down, and we’ll make exception.” But they weren’t all written down in a suitable form for that, and so I didn’t reveal my ideas about the laser until I had a chance to write them out, which I proceeded to do for the first couple of months after I got there. And then, when I did reveal my concepts of how a laser could be built and what it would do, or what it would be able to do, I was at first met with blank stares by the various people at TRG who could hardly conceive of an apparatus that could generate a beam of light which was coherent as it was generated. And it took quite a while to convince people that in fact, such a device as a laser was theoretically possible, and that if it was possible, it would be possible to achieve the conditions under which it would operate, namely a population inversion between a pair of states such that the transitions would result in the generation of light or emission of light by stimulated emission of radiation.
Bromberg:Was this mostly Goldmuntz and Richard T. Daly you’d be talking to.
Gould:No, actually, Maurice Newstein and Nicholas Salamin and several others, the theoreticians, and only the theoreticians could even think about it. The experimentalists didn’t really understand it. But also of course I did talk about it to Goldmuntz and Daly but they didn’t really react to it until these theoreticians had become convinced that there could be such a thing as a laser. Even though they were aware, of course, of the maser, the microwave amplification by stimulated emission of radiation, there was another step to go in thinking about the laser, which had to do with the fact that a beam was to be generated which was already straight and coherent, as opposed to the generation of microwaves in a cavity with dimensions of the order of magnitude of the wavelength, and thus the radiation from that would just go out in all directions, even though it was temporally coherent.
Bromberg:I see, so in other words, it was basically the special coherence which was —
Gould:— that was the exciting part of it. Aside from the excitement of being able to think of media and means for exciting those media which would produce the necessary conditions for the amplification. It was the idea of generating a beam, instead of radiation going in every direction, a beam that could be controlled or manipulated. That was the real excitement of it.
Bromberg:And there was also the problem — it wasn’t that well understood?
Gould:Well, it certainly wasn’t easily understood by the people I was talking to at TRG. And I had understood right from the very beginning, back when I wrote my first notebook in November of 1957, that the laser would have the ability to generate this beam, and that it could be focused, to produce intensities that were many orders of magnitude higher than any that had ever been achieved, or even occurred in nature, shortly after the Big Bang —
Bromberg:Was that the “Eureka moment” for you?
Bromberg:The discovery, the realization of the coherence?
Gould:Absolutely. And of course, as I’ve said before in response to that, it was the Eureka moment, but the Eureka moment will never come until you’ve stored up all the bricks and mortar necessary to be able to put that idea together. Well, anyway, after some time, maybe two months, of talking about this, and I should also add that I was not working on this to the exclusion of anything else. When I came to TRG, I received a dash of cold water, in that I wasn’t quite aware that in order to work on anything, in a company that depends for its living on contract research, you have to go out and get contracts, to do what somebody else wants done. And so I found myself working on several other contracts and research projects, and only being able to work on the laser sort of in off moments or time that I took off from work, which I did in order to work on this, because I was considering it still to be proprietary, in a sense, to me. So I worked, for example, on a frequency standard based on rubidium hyperfine transitions, microwave frequency standards, which were made to operate by optically pumping it. Something I could do, because my thesis work of course had to do with optical pumping of thallium beams.
Bromberg:So, you were talking to Salamin and Newstein and brought them around.
Gould:I finally did bring them around, and then everybody began to get very excited about this. And Dr. Goldmuntz said, “This is going to be revolutionary, and I’m sure that we can get money from the Advanced Research Projects Agency to work on it.”
Bromberg:So, in other words, it’s the middle managers you have to worry about. The president of the company is apparently a real proponent of this.
Gould:Right. Remember that Dr. Goldmuntz had a PhD in engineering. He technically understood. And the company was not all that big. At the time that this was happening, there may have been 30 people in the company. Eventually it grew to have about 200 people.
Bromberg:I’m very interested in just how decisions get made in industry to do a piece of research. I think that’s one of the things we want to keep in mind.
Gould:Well, it would be very different in a place like Bell Labs, which is an enormous laboratory, where anything that was carried along had to be approved by a host of people and budgeted and so on. But in a place like TRG, first there was very little money that the company had of its own that it could spend on any kind of projects, and so, the immediate effort always was to go to find somebody who would sponsor that project.
Bromberg:The first step was for the company to decide, yes, this is a proposal we’d like to make?
Bromberg:And that was Goldmuntz’s decision?
Bromberg:Is that right, do I have that right?
Gould:Yes, that’s pretty much right. Yes. And he knew right where to go, and went there, made contact with the people at the Advanced Research Projects Agency, and they immediately got very excited also. But I should say that, before that could happen before the Advanced Research Projects Agency could act, they had to see a proposal. So the notebooks that I was writing during 1958 had to serve several purposes — one, to be a basis for a patent application, another, to be the basis for a proposal to ARPA or whoever. And of course, the original purpose of the notebook, as you recall, was to provide a description of an invention that I wanted to except from the standard patent agreement, so that it turned out to serve all these various purposes, and it finally was put in the form of a proposal to ARPA about the first of December, 1958, and it immediately produced a tremendously positive response among the people at ARPA who were considering it.
Bromberg:And you say that it was Goldmuntz who really went out there with the negotiating. You weren’t talking to them nor were you also?
Gould:Well, I was also brought down there by him to talk to them, from a technical point of view, to explain things so that they could understand.
Bromberg:Do you have any memories of what that interaction was like, or what people were saying?
Gould:Well, I remember talking in a conference with a number of people on several occasions down in Washington.
Bromberg:Paul Adams, I guess, is one person who was particularly involved.
Gould:Adams — right. He, I believe, was on loan from Bell Labs — I’m not sure whether it was Bell Labs but that sticks in my memory. He became more enthusiastic than anybody else, and he was very persuasive, I guess, among his colleagues, and as you mention further down here on question 2, “Please talk about the contract negotiations with DOD as you remember them. What problems were ARPA most interested in pursuing? How did they decide to raise the contract sum to nearly one million dollars?” — Well, Goldmuntz decided early on to ask them for $300,000 for this project, which was quite a sum of money in those days, and I guess Adams and some of the others who were sophisticated about research realized that that just wasn’t going to be enough money to do what was proposed in that proposal, which was to investigate half a dozen different ways, different kinds of laser media. Instead of doing those sequentially, say, they wanted to do them all at once, in parallel, just to make sure that something would come of it as soon as possible, and to run six different research efforts simultaneously was not going to be accomplished for $300,000. So they proposed to up it to a million.
Bromberg:You had considered doing them sequentially?
Gould:Well, I hadn’t really considered very much the organization of that effort at all. I just had in my own mind, if I were going to work on this, what I would do, and I was not experienced in organizing a whole big group of people. I just had no management experience at all.
Bromberg:Well, certainly very often the government will ask for parallel development, and at this period of course, right after Sputnik when everybody was revving up, one could easily imagine that they might have liked to see parallel development.
Gould:Well, yes. Now, in connection with the enthusiasm of the people at ARPA, and I should add that although it was not known to me, there was a committee of consultants called in by ARPA to consider this proposal and give judgment on whether it should be supported, and that committee included people like Charles Townes and Peter Franken, and they gave a recommendation to go ahead with the project, and that was part of the reason that they jumped in like that. Now, bearing on that enthusiasm also, I’ll skip down to your question 13 on laser weapons — and you in that question say, “Towards the end of 1961, the Institute for Defense Analyses began to, get interested in death ray weapons. Did that have an effect on TRG research?’ Well, they didn’t wait for two years till 1961 to get interested in death rays. That was their enthusiasm right from the very beginning.
Gould:And the reason for the tremendous support of that project was primarily because of the possibility of such death ray weapons.
Bromberg:I see. I’d somehow just assumed it was because of stuff like radar, which you explain in the proposal, was one of the big [applications] — and communications and radar I guess were the things that you proposed as important applications.
Gould:Yes, but they immediately had in mind a powerful beam that could do more than just communicate. Now, actually, as I and others have pointed out, photons are really not a very good type of particle to make a death ray out of, because the wavelength of light being as long as it leads to diffraction, spreading of the beam over some distance, and the rate at which such a beam will expand due to diffraction depends on the wavelength, and if you’re going to build a ray gun, you really should do it with something that has a much shorter wavelength, which would then not spread. Why not matter waves? How about a bullet? It doesn’t spread at all as it goes (laughter).
Bromberg:Is this the kind of thing you were talking about when you met these guys?
Gould:I didn’t talk about that, no. Although I didn’t think too much of the idea of a powerful death ray , I did think that the laser would be useful for many other things, and I held back my reservations which had to do with diffraction spread.
Bromberg:By the way, I was struck by the difference between the notebook you gave me and the proposal. The notebook has many many applications, most of them civilian, and many of them for scientific instrumentation, whereas the proposal, as I remember, just had a little paragraph saying there are a few minor civilian applications.
Gould:Well, that was really Goldmuntz’s thought. If you’re going to write a proposal for the Department of Defense, you’d better emphasize the things that the Department of Defense would be likely to be interested in. So that’s the reason for that difference.
Bromberg:Well, did this emphasis on high energy weapons or high energy lasers at any rate then have an important influence on the way you began to set up your research program?
Gould:Yes. Well, actually, when we received that contract and started the program, we couldn’t work on everything, and the projects that were selected were selected primarily with the view of what could be probably most quickly brought to fruition. That was the starting point. All right, now, in question 3, the cesium maser. You’ve been talking with some of the Bell Labs people, I guess, who call it a maser instead of a laser.
Bromberg:Oh no, it was probably late in the day and I was tired. Sorry about that.
Gould:There was this little story I could tell relating to that. Townes and Arthur L. Schawlow and the people they worked with tended to call it an optical maser. They thought of it as an extension of the microwave maser. And I had coined this acronym “laser.” And as several years passed, the term laser sort of took over and became the standard term that was used to describe this device and name it. And there was kind of a little underground struggle over which name would come to be used. Many years later, when the LIA was founded, the name of that organization was the Laser Industry Association. That was the first name, and I became the second, maybe it was the third president of the LIA, and at the time that I became president of that organization, there was an endeavor to establish a cooperative arrangement between the LIA and the EIA, the Electronic Industry Association, and the EIA was a little bit miffed because the LIA sounded very similar to it in name. So there was an effort on my part to re-name the organization in such a way as to make the EIA a little happier. So we had a board meeting at one time, and both Schawlow and Franken were on the board at that time, and we were discussing what kind of a name change could we possibly make which would make the Electronics Industry Association happy, and ultimately, of course, it was changed to Laser Institute of America which had the same initials. But during the course of the discussion, Art Schawlow with his merry eyes said, “I have a proposal. Let’s call it the Optical Maser Association.” And we all had a great laugh, and Peter Franken said, “Art, forget it, you lost that battle long ago!” Well, that’s quite a diversion, but — Now, in question 3, on the cesium laser, “How was the team assembled for this work? What were the main lines along which you organized the research? What were the important breakthroughs, the obstacles? Who among your colleagues at TRG had influence upon the direction of this research? Did your DOD monitors have impact of any importance on it? “ Well, I should remind you and say that something which did have a tremendous impact on the whole project was the fact that it was classified before it started. And that I had been unable to get a clearance, although TRG went to a lot of trouble to try to get that for me.
Bromberg:Was that was something that was just gradually revealed, or did they try to get it when you first — I mean, did they only try to get this clearance once the laser project started?
Gould:That’s right. Once it was classified.
Bromberg:And then of course in my experience these people take forever in just giving you an answer.
Gould:Well, especially in a case like mine, where there were things that happened long ago in my background which would not make for approval, for security clearance So the project was organized by other people, and in particular Dick Daly, later the president of Quantronix, was put in charge of it. If there hadn’t been this security clearance problem, I no doubt would have been in charge of it. So I did not really have any influence on what projects were selected to work on within the whole laser project. My position with respect to the project was that if they cared to, anybody within the project could come and talk to me and ask questions of me as a consultant, so to speak. But generally speaking, that did not happen. So I really didn’t know too much about what was going on, except that I did hear, there wasn’t much progress being made, and I began to get frustrated and annoyed by that, and so, after six or eight months when nothing had been accomplished, at least no lasers had been made to operate, I spoke to Dr. Goldmuntz and others, suggesting that there was one laser that had been proposed in that proposal which I was certain would work, and it should be worked on. And that was the cesium laser, pumped by a helium lamp. I was certain it would work the way it was described because everything was calculable about transition probabilities, and the intensities that could be achieved in the lamp, were known and so you could just calculate that it was going to work. But of course, that did not take account of the difficulties of dealing with an alkali element which is very nasty stuff.
Bromberg:In terms of corrosion and so on?
Gould:Yes. So there were just technical problems about building one, which had to be dealt with. At any rate, I did have an influence to the effect that Dr. Goldmuntz, Dr. Kotik who was in charge of another department but one of the board of directors of TRG, and Dick Daly agreed to start a sub-project to work on the cesium, the helium-pumped cesium laser. And they put two people on that project, Dr. Stephen Jacobs and a younger fellow named [Paul] Rabinowitz who had just come on board at TRG, to work on that. So among the people at TRG who had an influence on the direction of the research were primarily Dick Daly and certain other people within the project who determined what was going to be done, not me, except in this one instance of the helium-pumped cesium laser, but even there, I was unable to determine how it would be done. I had such confidence in the excitation process of cesium that I believed that you could just build one and it would work. But Jacobs, who was the senior of the two people who worked on that, was a more cautious type and took the attitude that many physicists took in the early years of working on lasers that you had to sort of prove that it would work before you turned it on, so to speak. That was the way Bennett and Javan went about it.
Bromberg:As opposed to Maiman?
Gould:Well, Maiman himself also did. He first measured fluorescent intensities and lifetimes very carefully before he finally put one together and turned the switch and it worked.
Bromberg:So was that part of the background behind that paper on optical pumping of cesium vapor which was published in the JOURNAL?
Gould:Yes. Precisely. Many fluorescence measurements were made and intensities measured, to establish experimentally that in fact, if you built a cesium laser, it would work. And when they did build it, it did work. But in the meantime it took a year and a half or so to make all those measurements, thus delaying [the operation of a cesium laser].
Bromberg:This is the first time I’ve gotten a real appreciation of what that must have felt like emotionally.
Gould:Well it was very frustrating, knowing that other people were working toward a laser, and we had a chance to build the first working laser, but it wasn’t accomplished because they didn’t go and build a laser, they went and made measurements, and in the case of the solid state lasers, they didn’t build a laser, they started learning how to grow crystals. No effort was made to make a solid state laser until Maiman demonstrated his. Then all of a sudden there was big excitement, and within a month or two they had built one that worked. But only after Maiman had demonstrated you could do it. Now, it takes courage to do something that’s never been done before, and most people don’t have that much courage, so they’re going to sort of work around it from the outside and make a lot of measurements that finally prove that if they screw up their courage, it will work. Instead of just going ahead and trying it as proposed, and then possibly being disappointed in its failure if it didn’t work, but — well, the approach of all the physicists, and it was mostly physicists who were involved in early laser research at other labs, the approach is always the same within academic research — learn everything about it before you finally try it.
Bromberg:Are there any other examples of the opposite behavior, just to orient me a little bit? Either that you were involved with or some case of interest? I just think this is a very interesting thing that you’re talking about, as a typical —
Gould:The psychology of it is interesting.
Gould:Well, there was another example that would illustrate this, at TRG, actually. Down in your question 6, you mention the crossed roof prism interferometer, and another version of that is the cube retro reflector interferometer.
Bromberg:“Please tell us about this piece of research. Was Peck’s sojourn at TRG of interest as an element in this story?” Yes. And the reason for my proposing these prism interferometer was that I realized, from the very beginning, that trying to line up two flat mirrors, and I did not think of using curved ones as was later proposed, in order to ease the alignment problem, to line up two flat mirrors to the necessary precision, separated from each other by a meter or so, when you didn’t have any source of coherent light, of light sufficiently coherent to have an interferometry, pattern between the reflectors — that was the big problem. It was one that [Ali] Javan, [William] Bennett and [Donald] Herriot really struggled with over at Bell Labs, and finally they achieved their first lineup just by banging on the apparatus and having it vibrate all over the place, and eventually accidentally for a moment lining up the mirrors and getting a flash of radiation. I realized that that was a serious problem, and I conceived of the prism reflectors as a way of dealing with the problem, because it was possible to make the prisms with very precise facets, which had retro reflective properties, so there would be an automatic lineup no matter how you oriented the prisms. You could move them around and still maintain in effect perfect alignment. And I tried to get Jacobs and Rabinowitz to use that reflector, instead of trying to line up, without any means for doing so, two flat reflectors, and they simply didn’t do it. It was too radical an idea. But I did at least convince them that we should get somebody in to examine the modes of such a resonator in great detail, and that turned out to be Edson Peck, who, during the summer of, I guess it was 1960, —
Bromberg:I didn’t bring that date with me.
Gould:— he was a professor at Northwestern University. And he agreed to spend his summer at TRG and do a theoretical analysis of the cube corner retro reflector resonator, which he did, and his analysis indicated exactly what I said it would do, which was to essentially maintain the line-up to the degree of accuracy with which the facets of the prism are accurately oriented with respect to each other.
Bromberg:Was he necessary because that was also classified?
Gould:Well, he happened to be an expert classical optical physicist. He was eminently suited to do that analysis, and I guess Dick Daly did not want to devote anybody’s time on the project to this, but he was willing to hire Peck for the summer to do the analysis. And despite the outcome of that analysis, which was positive, supported what I said it would do, in much greater detail than I had analyzed it, they still did not use it, in trying to achieve line-up for the cesium laser. And here I have to say, I hope Steve will take it well, that a demonstration of a flat mirror and cube corner retro reflector resonator was not demonstrated experimentally until a moment when Steve went away on vacation, and I said to Paul Rabinowitz, “Look, let’s try this thing out, “and we did, and got beautiful Fabry-Perot rings photographically from it, and then, when Steve came back, we used it. By this time, the helium neon laser had already been demonstrated at Bell Labs.
Bromberg:Was this your cesium laser as it finally came out?
Gould:I don’t believe it was ever used with the helium-cesium laser. Because of the long wavelengths involved in it. We didn’t have prisms that were transparent at those wavelengths. But it was tried out, more or less, after the fact, using a helium neon amplifier, and it really was just marvelous the way it worked. You could hold that prism in your hand and it would continue oscillating! Instead of the painful line-ups that were necessary with ordinary mirrors. I remember in the lab, Gerry Grosof just picked up this prism and held it in front of that tube with a flat mirror at the other end and it started oscillating. Oh well! So, “Who decided what was to be done?” Well, I didn’t have all that much influence, but I did have some. You asked me a while back, what was I doing? Well, two things. First, when the project started. In July or so of 1959, it was clear that this project was going to support, and need, a dozen people or so, and they simply didn’t exist at TRG. There were only two or three people available to work on it. So one necessity was to go out and find suitable people qualified to do that kind of work, and one assignment I had was to go out and give some lectures and try to get people to come and join us. But I was faced with the awful problem of not being able to tell them what the project was all about because it was classified, and still trying to convince good people to come. That was a tough assignment.
Bromberg:Is that when Benjamin Senitzky came? He was at college with you, wasn’t he?
Bromberg:He was at Columbia.
Gould:Not while I was there. Ben Senitzky I take it back. He was there, but I think he was a nuclear physicist or something. At any rate, our paths didn’t cross. I only vaguely remember, now that you mention it, that he was at Columbia, but he certainly was not close to me, and he was not an experimentalist. So I didn’t know him there. He came. Steve Jacobs came. Ronald Martin, who is now head of Argonne Labs., and a number of other people. So part of my time late in ‘59 was spent trying to mobilize the people to work on this project. But most of the time, and for the next couple of years, I was working on other projects entirely, and one of them was a microwave amplifier research project, for which a contract had been obtained from the Rome Air Development Command, to study, or try to conceive of new types of microwave amplifiers.
Bromberg:Now, is this connected with this paper on side bands?
Gould:— yes —
Bromberg:— where the central frequency saturates and somehow the —
Bromberg:I guess that’s [question] number 15.
Gould:“What place did the line of research on millimeter wave amplification for use of sidebands of an absorption line have in your research career? Was this a major project and what was its history?” Well, it did have an effect on me, in that that was the way I earned my living during that period, and it was not major in the sense of being very well funded, the way the laser project was, but it was a substantial project. I think on the order of 50 or 100 thousand dollars. I can’t remember exactly. I hadn’t written the original proposal. Somebody else had written that. And the contract came through, and then all of a sudden everybody was thrown into the laser project, and I was left to work on this amplifier, this millimeter wave amplification study. So the way I proceeded with it was, I sat down and I actually thought of about a dozen different new types of amplification processes that might be studied, that might be useful for generating millimeter waves, but one of them had to do with [the] saturation process of atoms or molecules, saturation in the sense that — well, it’s hard to say in a non-technical way how this worked. If you saturated the transition between two levels in an atomic or molecular gas by a strong microwave signal from some oscillator such as a klystron or magnetron, and at the same time, you mixed with it a weak signal that you were trying to detect, the combination of those two , interacting with the atoms whose transition was saturated by the powerful source, [yields a] response such that your weak signal would be amplified when it came out the other end. There’s a non-linear process which has been well worked out today; in many different ways that kind of interaction has been put to use. But at that time it was rather unusual, and so I wrote a report under this contract listing all these different possible types of amplification processes that might be used, but putting some emphasis on that one. And it happened after that report was written, the Rome Air Development Command enthusiastically extended this contract, gave us an assignment to work on several of these processes experimentally, as well as theoretically.
Bromberg:That’s characteristic a little bit of your papers, isn’t it that they seem, very often, to say, “Let’s see all the ways we can do this.”
Bromberg:Or “let’s see all the things that can go wrong” or whatever.
Gould:And being creative, in the sense of thinking up new ways that processes can be used, say for a laser, or for amplification of microwaves. But often, having so many ideas to get down, [that were] often arising intuitively I seldom really analyzed any of these things out to the ultimate, although in each case I analyzed it far enough to convince myself that it was going to work. I have my beefs with the theoreticians! They can work for years to analyze a process out to the ultimate, and then miss the point. Anyway, just as we were about to start on the extension of this contract, I got sick with mononucleosis and was out for a couple of months. And two other people went to work on the project and proceeded to work on the wrong thing, so to speak, and they never did demonstrate any of these processes, including this particular saturation process, experimentally.
Bromberg:So that would have been Senitsky and Cutler, it says here.
Gould:Yes. Years later, when Senitsky went to the Polytechnic Institute of Brooklyn, he continued work on that process and did demonstrate it. The name of the amplification process which I gave it was the Constant Loss Amplifier.
Bromberg:That’s a serious name?
Gould:Well, it was a description of the way it worked, in a sense, in sort of half jocular, half serious… The process was such that a weak signal is amplified as the strong saturating signal is absorbed. It’s kind of a transfer of energy. It was interesting that some ten years later, a fellow — I believe his name was Nethercot(?) — who had been at Columbia about the same time I was and who went to IBM, thought of the same process, and published a paper on it, and only after that paper was published did he learn that in fact we had developed this idea ten years before.
Bromberg:And published it.
Gould:And published. Now, you ask here in question 4, “From the materials at the Columbia Radiation Lab Archives, I gather that you had a cooperative relation with the Townes group at Columbia during the cesium work.” You would like a picture of my interactions with them. Was I also in touch with groups at BTL? “In general, which interactions with groups outside TRQ do you think were important?” Well, I would characterize the relationship between the TRG group, namely Jacobs and Rabinowitz, and [Isaac] Abella, [Herman] Cummins, Oliver Heavens, Townes group at Columbia; I would characterize the relations as friendly rivalry. And I myself did not have any interactions with them, or very little, but Steve Jacobs was a good friend of Cummins, and they interacted quite a bit, I guess. Perhaps passing information to each other as to their woes and problems in dealing with cesium. And as you probably know, they never did get an optically pumped gas laser to work there. At first they spent a lot of time working on a potassium laser pumped by a potassium lamp, as suggested by Townes, but eventually they gave up on that. They couldn’t get enough intensity out of the potassium lamp. And they started to work on the same helium-pumped cesium laser which was eventually demonstrated at TRG. “Were we in touch with groups at Bell Labs?”
Bromberg:That’s mostly a question about, were there outside groups that entered the picture importantly.
Bromberg:It might have been in other industries. Some of these little places.
Gould:Well, we didn’t know at first that Javan and Bennett were working away at the helium-neon laser. Javan gave a paper on the concepts-of that laser, at the first Quantum Electronics Conference, so I realized that he had thought of that by then. And although it was in my proposal, and patent application, it was not worked at TRG. But other gas discharge lasers were, such as the krypton-mercury mixture. And they actually demonstrated a sufficient population inversion to produce enough gain to make that laser oscillate. They had about a 1 percent calculated gain from their measurements, which would have been quite sufficient to make it oscillate, as was demonstrated by Javan and Bennett, who only had also about 1 percent gain, with helium-neon. But they were frightened by such small gain, when the losses in the cavity would be on the same order of magnitude or bigger. So they decided not to try it. It was another case of making all those measurements, but not daring to try it!
Gould:Anyway, other work at BTL. I guess we must have been aware, somebody must have been aware, not I, that Schawlow and some colleagues worked on rubies for a while, with measurements which indicated to them that the quantum efficiency of ruby was very low, therefore not a good candidate for a laser. Schawlow in fact came to TRG, at Dick Daly’s invitation, and gave a lecture on the subject, and concluded from his fluorescence measurements that nobody was ever going to make a ruby laser oscillate. And at that, Dick Daly and his group, who were primarily the ones working on solid state lasers, immediately dropped any further work on ruby. And a few months later, Maiman proved that one.
Bromberg:Right, Schawlow went back to working on ruby.
Gould:Yes. They reproduced that at Bell Labs very quickly after Maiman demonstrated it.
Bromberg:In fact, there’s a very nice memoir that Schawlow wrote, and one of the things he says is that just a few weeks after the Maiman announcement, he got a call from TRG saying that you people had made a ruby laser work.
Gould:Also. Yes. They had the rubies there that were necessary to do it, but they had been put away on a shelf, after they learned of Schawlow’s measurements. Maiman was struck by curiosity as a result I guess of Schawlow’s work and also the work by Irwin Wieder, — there’s something inconsistent about the reporting of fluorescence intensities, and Maiman wondered where the energy was getting to. It was not apparently getting out of the ruby in fluorescence after being absorbed.... Both Wieder and Schawlow reported low quantum efficiencies for the ruby fluorescence. And Maiman may have had suspicions about those measurements, and perhaps he suspected self-absorption or trapping, which was indeed the case. At any rate, he made his own fluorescence measurements, and I’m not sure what his apparatus was like for doing that, but if he was suspecting the trapping effect, he did the measurements in such a way as to avoid that. At any rate, he came up with very high quantum efficiency for rubies, and that encouraged him to go ahead and build one. And everybody else who had been working on these things, such as Bell and TRG up until the time they quit, had therefore the necessary rubies in the lab already to repeat Maiman’s ruby oscillator very quickly.
Bromberg:Do you remember what people were saying at TRG when those reports came out?
Gould:The work was still classified. I didn’t even know anything about it.
Bromberg:But you must surely have read in the paper about Maiman — in ELECTRONICS or wherever.
Gould:Yes, when it was finally published. But it wasn’t published for several months after he first succeeded in making an oscillator. But by the underground grapevine, Schawlow, Ronald Martin, and Dick Daly heard about it very quickly, and repeated it; but I was unaware of what was going on. There were other interactions with people, outside TRG, which were important to me. This work on lasers was actually in the context of microwave spectroscopy and the rapid development of what later came to be called quantum electronics. And I knew a number of people who were interested in this field and working in it. Now, you recall that I was not working on lasers all at this time. I was working on microwave amplifiers. And so it was important to me, not to the laser work particularly, what people were doing in that area. And so I interacted with people like James Wittke and Peter Bender and others who were active in this field. And they had more influence on me and what I was doing than the people who were actually working on lasers.
Bromberg:I see, OK. Ironic, after you had decided not to work on the optically pumped maser, after conceiving of it back in 1956.
Gould:Incidentally, you mentioned that optically pumped maser. When I got to TRG, and learned the cold facts of life, that you had to get contracts to support whatever you were going to do, one of the projects or inventions that I had thought of was that optically pumped maser, and of course that was already written up in a note book which I had written back in 1956, and I was able to come to Dr. Goldmuntz and say, “Here is this invention that looks interesting, and maybe we could make a good frequency standard out of it, “ although not much power was expected from it. Since it was already written up, it was very easy to write a proposal for that. And I did so, about the middle of 1958, and Dr. Goldmuntz found a potential sponsor to whom that could be submitted, and we got a contract to work on that optically pumped maser. A rubidium maser. The alkali element rubidium was selected as the medium. And the contract was actually from the General Electric Company, and was a subcontract under some very large project that they were working on. I’m not sure what that project was. I don’t know much about that project. But we went to work on it, and worked on it, beginning somewhere around November of ‘58 and on through the spring of ‘59. But then all of a sudden, General Electric’s contract ran out and they didn’t get a renewal, so they didn’t renew our contract, so the work on that just stopped in the middle. And although the apparatus was partly built, it never got completed. One of the reasons I was interacting with Peter Bender quite a bit was because he had similar ideas. Another type of optically pumped rubidium maser and we interacted with each other and stimulated each other.
Bromberg:Was this relationship to Wittke and Bender, does that have anything to do with the fact that you knew Dicke’s work? This was part of the question no. 7.
Gould:Well, yes, number 7 — “When was my patent application written up?” I mentioned Dicke’s 1958 patent, which was not so commonly known then. Townes and Schawlow did not seem to know of it.
Bromberg:I’m not sure of that, by the way.
Gould:I think Townes, well, I don’t know if he knew about Dicke’s 1958 patent or not, but he certainly was aware of Dicke’s work. I have spoken before about how fertile the atmosphere was at Columbia Radiation Lab, due to the presence of all those exciting, productive people like Townes and Kusch and originally Rabi started it all there, and others. Well, Dicke at Princeton also had built up a laboratory that was a very exciting, fertile one, which was working on microwave spectroscopy. Dicke himself was a very inventive person, and many ideas came out of that work, such as the idea of super-radiance. Dicke did have this patent application on a maser in which he saw a possibility of extending it to the millimeter waves, the high frequency range. Well, when you write a patent application, though at that time this wasn’t required you’re expected to mention any prior work that relates to what your patent application is about, and since I was aware of Dicke’s work, I mentioned it in the patent application.
Bromberg:You don’t remember how you came to know of this?
Gould:Well, somehow in the fifties, anybody working in microwave spectroscopy, (there weren’t that many labs around the country working in it), would be aware of the work done, at least in a general way, in other laboratories that also worked on microwave spectroscopy. Dicke’s lab at Princeton was an important microwave spectroscopy lab, and good work was being done at Harvard.
Bromberg:And the MIT group, would that be important?
Gould:And MIT. Yes. I’m trying to remember the names of people.
Bromberg:At MIT the only name that I can think of at the moment is Strandberg.
Gould:Yes. I knew him. We had him as a consultant, in fact, at TRG. At some period in the laser project.
Bromberg:He mentioned that he did some consulting earlier on at Hughes. That’s interesting.
Gould:Well, he knew [???] I guess.
Bromberg:Well, that was very early, no that was way back.
Gould:Prior to that.
Bromberg:I don’t know if he was still there.
Gould:Well, there was Pound at Harvard, and Bloembergen?
Gould:That was the important productive group. Bloembergen had invented another way of exciting microwave masers. So I was just aware of them and had read those papers that related to what I was doing, which was optical pumping. And several of Dicke’s papers were relatively important. Wittke was out there. He was a graduate student, I think, or maybe a post-doc.
Bromberg:Yes, he was a Dicke graduate student.
Bromberg:So was Bender.
Gould:That’s right. I’d forgotten Bender was his student.
Bromberg:Well, actually you’ve pretty much finished question 7, in all the things you’ve said. Now, there’s question 5, do you want to speak to that one before we go further?
Gould:The first Quantum Electronics Conference. It was very exciting. It took place after our project got classified. So I couldn’t talk about lasers there.
Gould:But I went there, and was very excited by it, and I was particularly frustrated because Javan gave that paper on helium-neon, when I had thought of it a year before that and couldn’t talk about it.
Gould:That conference was actually, am I mixing it up with the Optical Pumping Conference at Michigan? Anyway, there were a number of papers given at that first Quantum Electronics Conference about masers. It was mostly about masers. But all kinds of related work in microwave spectroscopy and some optical work.
Bromberg:The optical work was by Schawlow, who gave a general paper, and then Javan gave that He-Ne paper.
Gould:Did Peter Franken give a paper at that conference?
Bromberg:Well, I don’t recall. I would have to look it up.
Gould:Anyway there was an air of excitement and a feeling that big things were going to happen in this field, and of course they did.
Bromberg:That’s something you don’t pick up just from reading the PROCEEDINGS. Even though the laser was a very small part of that conference —
Gould:— that’s right —
Bromberg:There was a sense that —
Gould:— something was going to happen that was important, and nobody was quite sure what it was going to be.
Bromberg:I guess Maiman was there giving a microwave paper at that conference.
Gould:Yes. But already he was working ruby at that time, I think, I’m not sure. Maybe he started just after that.
Bromberg:The Optical Pumping thing at Michigan, should I know of [it]? Is that something I should look into?
Gould:Well, that was certainly very important as far as I was concerned, because optical pumping was the first way I thought of for exciting a laser medium, and also it was thought of by, in fact it was thought of by Townes back in ’57. As a way of pumping a laser medium. He thought to use a potassium vapor lamp to pump a potassium “optical maser”.
Bromberg:I’m sorry; I cut you off in the middle of your description of that meeting.
Gould:Well, that Optical Pumping Conference certainly was important, in that many different applications of optical pumping in spectroscopy were talked about. It served to advance the state of the art of how to achieve population shifts such as was necessary for creating laser amplification media but I don’t think there was mention at that conference of any laser as such, as was later mentioned in the Shawanga Lodge Quantum Electronic Conference by Javan. And at that conference, I don’t believe Bennett had yet come down — or maybe he had, I can’t remember the timing for sure. Javan had invited Bennett to come down from Yale and take off a year from his work as a professor at Yale to work with Javan on the helium-neon laser. He must have already been at Bell Labs at that time, which was in the fall of ‘59, but the paper was nevertheless given just by Javan. Even though they worked together, Javan and Bennett, Bennett was a little unhappy at that time, just because of something like that paper being given by Javan without Bennett’s name on it, and we have to give a lot of credit to Bennett for the success of that helium neon laser, because he was a very careful experimenter and knew a great deal about spectroscopy. That was exacerbated a little later when Javan actually wrote a patent application in his own name without Bennett’s name on it. That didn’t sit too well.
Bromberg:Is your acquaintance with Bennett coming out of this period when he was consulting and you were working with frequency standards, or did you already know him?
Gould:Oh, I knew him before that. He was a graduate student at Columbia also.
Bromberg:I see. You knew them all then. Javan was there.
Gould:Yes. But I got to know Bennett better as time went on, and then he became a consultant to TRG. We got a contract on optical frequency standards and he contributed to that. We even wrote some patent applications together, on the collision lasers we’ll talk about later. So, of the conference at Schawanga Lodge. Aside from the excitement of the subject matter of the papers and this feeling of something’s in the air, the air is pregnant with striking new developments coming; it was also just kind of fun at that conference. And I remember that. I guess Professor Townes must have had a lot to do with organizing that conference.
Bromberg:Yes, chairman I guess, of the organizing committee.
Gould:And he invited a number of Russians to come, which they did, including Basov and Prokhorov of the Lebedev Institute, and I remember an incident that occurred. Here were these important people from Lebedev, by invitation to the conference, and they and several people at the conference had a big party one of the nights, and Javan was there, and they all, got drunk on vodka, and Javan, who had a sports car at the time that was barely big enough to carry two people, invited everybody out for a spin in his sports car, including Basov and Prokhorov. And they somehow got off the road, in the woods up there in the Catskills and got stuck in the mud in a swamp. So everybody had to jump out, including the Russians, sinking up to their knees in this mud, and lift Javan’s little car back onto the road again. Another happening at that conference which led to an interaction with the Russians which was of some importance later on in the development of the laser. There was a fellow named Pat Thaddeus who was a student, I think of Townes, who, and at the suggestion of Townes perhaps, in order to be as good a host as possible to the Russians, at the Shawanga Lodge meeting, set out to learn Russian, and in about three months he learned it well enough to actually speak Russian. And so he acted as the sort of host for the Russians, and so they liked him very much for that and invited him any time that he was coming to Europe to come and visit The Lebedev Institute. About a year later, there was a publication by a graduate student and an academician named Fabrikant. The Russian academicians were exceedingly important, of course, in Russia. A publication which stated that they had achieved a very high gain in a gas of, what element was it? Mercury? I can’t remember now, it may have been mercury. I’m not sure which element, but the transition in which a very high gain was achieved didn’t look reasonable to me. But if that Russian report: were correct, they were way ahead of anybody in the United States in producing a powerful gas laser. So that was rather shocking. And we had to decide whether we were going to start another project in order to confirm or deny that report. But it looked fishy to me; because the transition was between two levels that I didn’t think, on the face of it, it would be possible to get a population inversion. And this work was supposedly done at the Lebedev Institute. It dawned on me that maybe Pat Thaddeus was going to be in Europe for a certain conference that was going on, and could he do a little detective work and find out about this? So I called him up, and indeed he was going to Europe, and I told him all about this report of a very high gain in a gas discharge medium, and said, “But it doesn’t look right to me and I don’t want to waste time and money from this project on it.” This might have been after the project was declassified, I guess, because I was involved with that.
Bromberg:Now, we want to get that down here. When was it declassified?
Gould:I think it was declassified in 1962. So it was a little after the helium-neon laser had been made to work, and possibly even after the helium-cesium laser. But neither of those was a powerful laser, and this one was going to be, according to the report. So Thaddeus got all interested in that detective work, and he took up Basov’s invitation to come to Lebedev Institute, and he proceeded to do that, and at a certain point while being shown around Lebedev Institute, talking with people there, he raised the question of this reported laser, and the way Thaddeus told it to me, Basov got all embarrassed and didn’t want to talk about it. It became clear that it was all a mistake. Improper measuring techniques, which in fact said there was, gain there when there wasn’t. So when Thaddeus got back to Paris, he called me up from there and told me what he had learned, and we all heaved a sigh of relief and did not make any attempt to reproduce that work.
Bromberg:Now, once it was declassified, did you then begin to move into this full time?
Gould:— Yes. The last of the microwave amplification contracts from RADC had already ended just about that time. So I did start working on that laser project, yes. And that was when I thought up such things as the photo-dissociation of thallium bromide, and the work on laser frequency standards with Bennett.
Bromberg:And also the collision laser work?
Gould:Yes, the collision laser works. That came after the declassification and after I started working on the project. Now, that story about Pat Thaddeus the scientific detective isn’t quite finished yet. Another person who read that report was James LaTourette who later came to TRG but at that time he was working in the General Electric Lab. He read that report, and he was struck by the high gain and the amount of power that could be expected if it would work, so he set to work to reproduce it. He spent a year and a half or two years working on it with total lack of success. Obviously it was a — I don’t want to call it a fraud, but it was a totally mistaken report. But he didn’t have the good fortune to have access to Pat Thaddeus, so a year and a half of his life went down the drain trying to reproduce that thing.
Bromberg:Kind of an instructive story.
Gould:I think he actually published a paper saying that he did not get the same results, something like that. That may have brought him to our attention, because it was shortly after that that we hired him to come down to TRG. And he later on went with me among others to Polytechnic Institute in Brooklyn in ‘67, and he’s still there. We’ve already discussed how TRG was able to reproduce Maiman’s laser oscillations within a month or so after they heard about it, which was before it was published, and you asked the question “What did TRG proceed to do with their laser?” Well, actually, the first ruby lasers did not produce a very coherent beam, because the quality of rubies available was terrible. What looked good as a gem was not nearly good enough to be the material for a highly coherent laser. So a lot of work was done to characterize the kinds of oscillations in the ruby, to determine what had to be done in the way of improving materials, also partly because it was a very complex phenomenon [that] occurred in the pulsed ruby laser, in which the pulses produced a very uneven rapid series of power spikes. It was temporally incoherent as well as not very especially coherent. So, work under the general umbrella “laser contracts”: from then on, there was a substantial amount of work done on characterizing and improving ruby lasers which produced the first practical applications of any laser, namely range finders.
Gould:TRG got a range finder contract and worked on that. And in fact, one of the first products they had actually was a ruby range finder.
Bromberg:Were you personally involved with that? I don’t know the time.
Gould:No. I wasn’t. It started before the contract became declassified. But they also had in mind to produce products for general use, a ruby laser to be sold as a product, a commercial product. I actually was the one that named that laser.
Bromberg:What’s the name?
Gould:Well, there is this bird, the Red Eyed Vireo.
Bromberg:A real bird?
Gould:A real bird, yes. Nobody had ever heard of it, but they accepted it as a name. Well, what was behind the decision to bring out the Vireo? Simply to get a product onto the markets. We tried to develop some business out of our laser development and research. I think a few of those were sold, but it was probably too early for such a product and it didn’t really take off.
Bromberg:Well, I do have a question down there, 11, about the interaction with the physicians on that. They were apparently using that Vireo, at least one of them.
Gould:In your question 11, you ask about the relation between our work and Milton Zaret on optical, ophthalmological effects, and also did TRG sales group get involved with this kind of collaboration between research staff and customer? Would any R and D activities in this case on the Vireo laser be inspired by the collaboration? Well, I was not involved in that work with Milton Zaret at all. There was a fellow working at TRG named Gerry Grosof who although he was a physicist came from a family that had many medical doctors, and he knew Zaret among others and the two of them worked together to investigate what might be done with the laser, and in fact they demonstrated the first repair of a detached retina with a laser.
Bromberg:I don’t know. We might keep this question in mind though if we do get to a point where something you were personally working on became commercialized.
Gould:Well, I just wanted to say that I find that one of the many interesting ironies about the ruby laser was that the ruby laser that was built at TRG under a military contract should have first been put to a practical application by repairing a damaged eye. (That is one of the nice little ironies that I like.) But, as I say, I did not have anything to do with that myself. Generally speaking, the TRG sales group, that is the people who worked on trying to develop a laser product line, was not involved in developing research contracts. The people who got research contracts were usually the people who were going to work them.
Bromberg:And this was really a research case.
Gould:But of course, there would be interactions between the sales group and possible customers, and I’m sure there would be some feedback. At Optelecon where I work now, most of the company’s income up to date has been in contract research and development, on optical communications systems. But we do have a standard telecommunication product line, transmitters and receivers for the ends of optical fibers, and those two activities normally are fairly separated from each other. But occasionally a request comes in to that product group which is handed over to us in the R and D end of the business, if there’s any potential for development. So there are interactions. But the effort to make products and sell them is quite a different kind of effort from research and development. In fact, they’re not generally very compatible.
Bromberg:In other words, we should be talking to some people who are in that other end, too, if we want to get an idea of the business.
Gould:Yes. Well, Goldmuntz and Daly, Daly certainly was well aware of that, because that activity was carried on in his department, the department of quantum electronics. Have you spoken to Daly?
Gould:Well, you probably should. Yes, certainly.
Gould:In question 12, you raise the question of how these early conferences, such as the Quantum Electronic Conferences and the conference that was held at Polytechnic Institute of Brooklyn in 1963, compared with other later conferences, and who was involved, and participated in these conferences? Of course at the beginning it all really started in the academic world, and although TRG was a profit making company, the atmosphere there was more like a research department of a university, at least in the early days. And most research and development companies do have that kind of an atmosphere. Certainly at Optelecon we also have that atmosphere, except on the commercial end. And when you mention industrial that connotes to me something quite different from the way things were at TRG. When I think of industrial, I think maybe of General Motors Company developing uses for lasers on their automobile manufacturing processes.
Bromberg:So really my distinctions are not fine enough there. So maybe you want to speak to the way the distinction should run.
Gould:Well, I would say that in the early years, the people who worked on lasers, whether they worked in companies or in universities, worked in similar atmospheres, and the work could be called academic, not basic research but applied research, but nevertheless an academic flavor, even though people did see the applications down the road. But as time went on, the emphasis gradually began to shift from simply demonstrating or inventing new lasers, to moving toward those applications. The Quantum Electronics Conferences of the first few years had that academic flavor to them, but later on, other conferences were started which reflected the move towards applications of lasers, conferences such as the CLEA, Conference on Laser Engineering and Applications, and later on the CLEO Conference, Conference on Lasers and Electro Optics.
Bromberg:That surprises me in a way because in the very beginning, it seems, Bell, and Hughes and you were working on things like optical communications and radar, and you get mention of these things as early as the fall of 1960, spring of 1961, beginning with these breadboard models of radar and what have you.
Gould:Well, we did have contracts, particularly for range finders, but the bulk of the work was still on developing lasers as such, and refining them and measuring their characteristics and doing things like working toward the use of frequency standards, optical frequency standards, whose potential applications were still more or less an academic type of effort.
Bromberg:Were these developments of the laser then going to be with certain things in mind, for example you would say to yourself, “Well, for communications we want more efficiency,” or were they just “We know that whatever the applications are, we’re going to want more efficiency?
Gould:— yes —
Gould:Yes. We did have several projects that had in view applications down the road, but they were sort of early demonstrations of capabilities that lasers had. For instance, the first demonstration of optical heterodyne detection was done at TRG.
Bromberg:You had a communications group or optical communications.
Gould:Optical heterodyne detection is a very sensitive type of detection, although difficult to achieve because of the shortness of the wavelength of light, but we did have a project that did demonstrate that, and we transmitted in fact, over a beam of light, music from station WQXR? Did I show you a picture of that?
Bromberg:No, but I’d like to…
Gould:I was talking about how the earliest work was done as applied physics, if you will, that had a rather academic air about it, even though people could see down the road the applications, and that what they were doing was going to lay the basis for those applications, one of the applications being in communications. And optical heterodyne detection, the technique that was used in super heterodyne receivers in the radio frequency region, to achieve sensitivity, was conceivable with light beams, and it was first demonstrated at TRG, and I have here a picture of that apparatus. This picture was on the cover of ELECTRONICS magazine.
Bromberg:I saw it there.
Gould:And TRG’s patent attorney, Bob Keegan liked it so much, [he was the patent attorney working on my patent applications], he liked it so much that he actually had some enlargements made, and he gave me a nicely framed copy of this. But it faded over the years, so it’s barely visible in the picture that he originally gave me, 20 years later. I thought, gee, I’d like to reproduce that again somehow, so I happened to have a copy of that ELECTRONICS magazine cover, and it was a reprint actually of an article written by Jacobs and Rabinowitz, who did this. So, although you don’t think of making an enlargement from a half-tone print such as the cover of ELECTRONICS, nevertheless it seemed to work very well, and this is made directly from that cover. The laser was actually down here in the lower left, and is split by this beam splitter into two beams, one of which is phase modulated, here, by a moving mirror, which carries on it the WQXR music, and they’re rejoined and detected together on this detector here, by what is called homodyne detection. That’s detection by mixing a beam, a reference beam you might call it, together with a beam of the same frequency, having information modulated onto it, as distinct from the two beams being generated by separate lasers, with frequencies offset from each other. Now, you have your question 9 about photo dissociation of thallium bromide, as a potential laser medium. Actually, that never did reach an experimental level.
Gould:It was an excitation technique that I thought of and proposed after I started working on the laser project, as a way of getting very high powered pulses out of a gaseous laser. But I guess there were too many projects competing for the money and the contracts. That one never got done — although years later, a similar type of excitation was done, using methyl iodide. The idea was that if you dissociate a thallium compound, not because it’s thallium but it happens to have a convenient energy level structure, that it could, in certain cases, be expected to dissociate into a metastable thallium atom and a bromine atom and then you have automatically a nice population inversion in the thallium, and the lower level would be kept depopulated by recombination of the thallium with bromine again. Anyway, as I say, many years later a similar process with methyl iodide was demonstrated. I don’t know if it has any practical applications yet or not. And of course, to get a lot of energy out of a gaseous laser, as compared to a solid state laser, would be important, because generally speaking gaseous lasers are much more coherent in their light output, especially on a pulse basis. But a project that we did pursue quite a bit is the collision laser.
Bromberg:OK, let’s talk about that.
Gould:In your question 15. Now, it was demonstrated at Utah University, or was it Brigham Young? — maybe it’s Brigham Young, some university in Utah, by a graduate student named Silfvast — I can’t remember his first name, but maybe it’s Henry Silfvast — under the sponsorship of his professor, and I can’t remember his professor’s name who suggested doing that experiment, but I think they were just trying out different vapors, which is an approach towards getting new laser transmissions that became the style, whereas people at the beginning very carefully worked out some medium and analyzed it and measured it and , as I said, proved it would work before they turned the switch on. Later on, the style was just to try everything and see what would happen. And the first laboratory to take that approach, which kind of nonplussed the physicists — the physicists take the careful, cautious, want to know everything approach —, was in England. During the war, and it still existed in 1963, a laboratory called the Services Electronics Research Lab, in Baldock, Herts, north of London, and I learned about that lab because — well, I should go back and say that that laboratory was very big in developing radar, which first started in England, and it still at that time was working on improvements in radar, especially generating powerful microwave pulses, for the purpose. But the head of that lab, Sir Harry Boots, marvelous character — he used to drive around in an old beat-up Rolls Royce — he was honored by the Queen for his contributions to radar, I guess — but he was finding a declining need for further work on radar development and he was looking for other things for that lab to do. So when he learned about lasers, he started to work. Various laser projects were started there, I guess in ‘62 or so. I heard about it, and when I attended the Paris Quantum Electronics Conference in ‘63, I made a point of going over to England and visiting that laboratory. Well, the way they started out was the exact antithesis of what anybody had done in the United States so far, namely, they took a great big tube and evacuated it and put air in there, and then whacked it with a big high power radar pulse, and it just flashed a lot of different oscillations, 50 different wavelengths. They had everything oscillating including carbon dioxide and oxygen and nitrogen. Whee! It was sort of like the approach that I was advocating at the beginning: build the thing and try it. Well, that kind of upset all the physicist types, but it also set off a new spirit of how to go about finding new laser transitions, and following that, literally thousands of different oscillating wavelengths were discovered , mostly just by trial.
Bromberg:OK, that’s something I have to look for them.
Gould:The first paper on that, perhaps.
Bromberg:Now, whose name would that be under?
Gould:I believe that Boots’ name was actually on it, but I’m not sure, and I believe it was the first observation of an oscillation in carbon dioxide, which later became a very important laser medium. It became important when it was mixed with nitrogen, because it has become the most powerful gaseous laser.
Bromberg:Now, is this connected with the collision laser?
Gould:Well, I got off on that tangent because a lead vapor laser was demonstrated at this Utah university by Silfvast and his professor , and what they really were doing was just trying things, — in the spirit of what had happened at Services Electronics Research Lab — and they published this, and I read it. At the time Silfvast and his professor did not publish any explanation of how it worked. It worked on a pulse basis; somehow it would pulse the light and then stop oscillating. It would work only on repeated pulses. Gas discharge breakdown. But I studied the structure of that atom, the lead atom, and realized how it worked, and the energy level structure was such, that it could work very efficiently, but only for a brief amount of time. I guess I don’t want to try to explain how it works here, now, but anyway, it worked in such a way that it was going to be an efficient and powerful pulsed laser. And when I realized how it worked and why it worked as well as it did, I looked at all the other elements in the periodic table to find those that would work the same way, and found some much better ones, including copper, which had an ideal structure for this type of pulsed laser. I also thought it might work in manganese.
Bromberg:When are we talking about, now?
Gould:We’re talking about probably 1964, it may have been, or even later, maybe ‘65. It was fairly late in the game, but it was a development of a new powerful class of gas lasers, which really was based on a type of mechanism which hadn’t been observed or used before.
Bromberg:There’s a paper out in applied optics, ‘65, without any submission date.
Bromberg:Well, on collision lasers.
Gould:Collision lasers, all right. Anyway, Bill Walter and a young fellow named Martin Piltsch were at TRG then, and built both a manganese and a copper laser, and demonstrated them, and the copper laser has been undergoing developments for all these many years, and finally reached commercial production just a year or so ago. But it’s going to be important, and will probably become more important as a pulsed laser than say even the neodymium-YAG(?) in applications of machining and welding facilities, the reason being that it’s about ten times as efficient as either the ion laser or the optically pumped solid state lasers.
Bromberg:Tell me about the collision laser —
Gould:— also called the cyclic laser — it can only work in cycles.
Bromberg:... we were just about to talk about the fact that special problems were posed by the high temperatures of that laser.
Gould:Well, let me remark that this laser, the copper vapor laser, was tried out at TRG first on the basis of an understanding of how the lead laser worked, as first demonstrated by Silfvast and it worked extremely well, and it was a demonstration that even at this late date, there were new types of lasers still being invented. And then I mentioned that there’s something like 12,000 patents on different lasers and applications of lasers! It’s a big field. But it also is a demonstration of the fact that as late as this, work was being done. In fact, for a decade after that. Still today new developments are made in lasers, not with the idea of a particular application, but just, here’s a neat kind of laser and what will its properties be? The academic, applied-research end of the laser effort. But there was a trend, as I mentioned, by the [time of the] initiation of these later conferences, which were regular annual conferences, moving towards applications and the personnel involved in laser work shifted from mainly physicists toward engineers. There are probably many more electrical engineers in the laser field today than there are physicists. There was a trend towards applications, and I myself have moved that way, into optical communications now, rather than laser work, although lasers are used in communications. So I characterize myself as an engineer today, and I haven’t written any physics papers in many years now. I changed into an optical engineer. And it’s all part of this same trend in the whole laser field, although lasers are being used as tools in basic research. Now, getting back to the collision laser, was it a special problem? Well, it wasn’t any great problem to build a laser which could vaporize copper, even though the temperature required is about 1500 degrees Centigrade, in the laboratory. You can always put it inside a furnace and heat it up. It was demonstrated that that laser had high efficiency for a gaseous discharge laser, and it clearly had good potential applications, especially since it produced visible light. But to make a product out of that did pose problems, because if you think about it, its efficiency would be lost if you couldn’t build a very efficient way of heating it up quickly and not wasting power on heat, and when we’re talking about applications in welding, cutting and so on, efficiency becomes important, because we’re talking about multi-kilowatt lasers which, if they’re ion lasers means a multi-megawatt power supply , because the efficiency of an ion laser is only a tenth of a percent, and the same is true for the neodymium-YAG and the ruby laser, very inefficient. So this laser promises to get you a kilowatt light bean for only 50 kilowatts in, whereas the ion laser, which also produces visible light, gets you a kilowatt for two megawatts in. Makes a big difference when you get to high powers. Anyway, the engineering was gradually worked out on the copper laser to enable the heat dissipated in the laser medium itself to heat the tube, in an insulated box. [It was] so designed that exactly the amount of power that was dissipated in the laser was what was needed to bring it up to temperature. And there is a copper vapor laser now on the market, and I expect that it will become important economically.
Bromberg:Did this turn out to be an important project within the TRG laser effort?
Gould:Well, even though it was late in the game as far as the ARPA sponsors were concerned, yes, it did turn out to be important, because it did produce a laser which clearly was going to be important, although it had technological problems to solve. Also it was important for me, personally, since I have a patent on it. Now, you ask in question 17, “How do you characterize similarities and differences between work at Brooklyn Poly and TRG? “ — very little difference. And that’s why I referred to TRG as being a more or less academic or applied research type of organization with an academic atmosphere. Very little difference, except at the university, Polytechnic Institute, we not only felt the pressure “to go out and get a contract,” but we had the additional job of teaching students in our schedule.
Bromberg:Does that make a difference in the way research goes, or the teaching is just sort of an extra that doesn’t react back?
Gould:— well, of course, this was a graduate school and the students were working on graduate theses, so a lot of the actual work, whether experimental or theoretical, was done by students. So a university can compete with a profit-making industrial laboratory because it has inexpensive labor, compared to what you have to pay to get good people into an industrial lab.
Bromberg:Did you find however that there were certain kinds of restrictions on what you should or would take up in the university setting that were different from the ones that you found in industry?
Gould:Generally a university will not develop and sell products. But almost anything else, at least in a place like Polytechnic Institute of Brooklyn, is fair game.
Bromberg:I was just thinking of something like this. Your students are cheap labor but at the same time you can’t give them anything to do that won’t eventuate in a decent thesis.
Gould:Correct. That was a requirement.
Bromberg:Does that affect the way things go very much, in your experience?
Gould:Well, it isn’t difficult to think of projects which would be of interest to say the Defense Department let’s say, early development work or research work which had in mind an eventual application, say, in the military , but which at the same time would have original content and serve for a thesis. It really wasn’t difficult to find projects like that.
Bromberg:OK, so it wasn’t a very severe restriction.
Gould:No. And. you might think, well, why should the military support a project which was not aimed at developing a weapon or something like that? Well, let’s take the case of laser weapons. Laser weapons, people had in mind in the Defense Department’s ARPA right from the very beginning. But here it is 25 years later and there still aren’t any laser weapons, operational, that I’m aware of. So why has the military supported this all these years? Well, they have because they still see the potential but there were many problems that had to be solved, some of which are certainly suitable for thesis work.
Bromberg:The other thing of course that occurs to me is that in teaching your mind might have been led into certain avenues which it might not otherwise have been, which reacted back on your research. Is that also just not a very good guess?
No. What you had to do in teaching was to teach the basics of the subject, to decide what you think are the basics of a subject, the basic theory of how lasers should work: diffraction theory, theory of modes of light, all those things that the student has to have as tools to be able to do the work, but they don’t stimulate, usually. Not in classroom teaching do you get stimulation toward new areas of research. It’s really a drain of energy. The best that can be said for it, as far as I’m concerned, is that you could get students interested in this area of research and work. And in fact, I never did like to teach very much, I guess you gather. I think I said at some point in our earlier interview that I was always interested in inventing, rather than basic research, and that what I was working on had to have some important application or economic impact before I really got excited about it, and that was still true of me while I was at Brooklyn Poly, and since I was hampered in spending time by having to spend time teaching, and other academic activities, it really got kind of dreary and I wanted to leave. In the meantime, about 1972, a gentleman by the name of William Culver, who actually was involved in the very early laser work at the Institute for Defense Analyses, and had later gone to IBM, and then got frustrated at IBM and decided to start his own company, which became Optelecon — he prevailed upon me to join him. The timing was such that it was very convenient, because just before then, Polytechnic Institute of Brooklyn was merged with the NYU Engineering School, and the Institute that emerged from that was the Polytechnic Institute of New York. That’s what its name is today. After that merger, times being what they were, there were too many tenured professors, and so the management made an offer of a full year’s terminal leave with pay to anybody who would give up his tenure. Since I was thinking of quitting anyway, I jumped at that. So that was my investment in Optelecon that year.
 Technical Research Group, Inc.
Department of Defense
Stephen Jacobs, Paul Rabinowitz and Gordon Gould, “Optical Pumping of Cesium Vapor,” J. Opt. Soc. America 51 (1961) 477
B. Senitzley, G. Gould, and Sylvan Cutler, “Millimeter-Wave Amplification by Resonance Saturation,” Phys. Rev. 130 (1963), 1460
William Thomas Silfvast
Session I | Session II