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Oral History Transcript — Dr. Charles Townes

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Interview with Dr. Charles Townes
By Dr. Joan Bromberg
At Berkeley, California
January 28, 1984

Charles Townes on choosing between working for defense and continuing work on lasers

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Charles Townes; January 28, 1984

ABSTRACT: Research on nonlinear optics at MIT, 1962-1967. Other laser research in MIT period. Responsibilities as Vice-President and Director of Research at Institute for Defense Analysis (IDA), 1959-1961. Interest at IDA and ARPA in lasers and laser weaponry. Contemporary evaluations of Robert Dickeís superradiance paper. Townesís change of research field from nonlinear optics to radio astronomy in the late 1960s.

Transcript

Session I | Session II

Bromberg:

So you came back to MIT in the fall of 1961?

Townes:

Yes, I believe thatís correct. It may have been August or September, somewhere along in there.

Bromberg:

My questions are really about the evolution of your research program there.

Townes:

Well, my primary job was administrative, and I had a clear understanding that I would spend one day a week on research while I was there, otherwise I was doing primarily administrative work. Now, I immediately looked for a grant to do something on quantum electronics. I must have some papers somewhere about what grant I applied for. I donít at the moment remember just exactly what its nature was, but it clearly was in the area of quantum electronics. I applied first to NSF. I had a very funny experience with NSF. Wayne Gruner, whom I knew pretty well, came around and said, ďWell, we have your application, but you know weíve got a lot of younger people to take care of, and would you mind withdrawing this, because weíd hate to turn you down, it would look bad on your record, and if you withdraw then we can go ahead and give the money to the younger people.Ē I said, ďWell, so far as my record is concerned, I donít care. If you want to turn me down, thatís your responsibility.Ē But he insisted, ďWell, you know weíve got a lot of younger people to take care of and it would just be a lot easier for me if you would withdraw it.Ē I wrote him a letter saying, ďSince you ask me to withdraw it, I withdraw it.Ē I was a little annoyed. I think thatís a poor way for NSF to operate.

So then I applied to NASA, as I remember, and NASA gave me quite a nice substantial grant, essentially all the money that I really needed at that time. I donít remember just exactly how long that took, but there must be correspondence on that, and exactly what I said the program was going to be. I donít remember what I said the program was going to be. But I think looking at what I said the program was going to be may be helpful in seeing what I thought quantum electronics was like at the time, or at least what parts of it I felt I wanted to do at the time. My plan was to have about one post-doctoral person and two students, as a way in part of keeping my hand in, but in part also, of seeing what MIT was like from the inside. Actually it was amazingly useful from the point of view of my administrative work, to see what really went on with students, because at a higher level youíd get certain reports as to what was going on, and they wouldnít necessarily correspond to reality. So it was helpful from that point of view, but personally I also just enjoyed doing research. Now, I guess Chiao and Garmire started work with me fairly soon thereafter. I donít remember the exact timing. But moderately soon, they got under way.

Bromberg:

Now, I noticed your first work was with Javan and Haus. I wondered if that had anything to do with the necessary time to get the funding for students.

Townes:

Well, let me see. Javan also came there pretty much the same time I did and at my suggestion. Javan of course had been a student of mine and I thought very highly of Javan. I knew he was interested in going to a university. So I suggested he be hired, and while it was not overt, I think in part MIT felt that it would be sensible to have a younger person working with me. I wasnít able to spend all the time in the laboratory. That was partly a courtesy to me, to invite somebody that I thought was good, and who would of course also be a good permanent faculty member. So Javan came there really at my instigation and both he and I expected to work together right away, which we did. Of course we did independent things too, as well as working together. My working with Haus was more accidental. Haus was in the field and interested in noise and laser properties, and we talked a good deal. He had a student, Ken [T. Kenneth] Gustafson, who worked with me a good deal eventually. He was Hausís student but I saw a lot of Gustafson and we published together. It was just a sort of a loose association and we had discussions together, and Haus was frequently involved. I think, as I remember the only paper I published with Haus was on the noise problem which was raised by Barney Oliver.

Barney Oliver was initially claiming that heterodyne detection was more sensitive than what the paper I had written with Serber on the limits of sensitivity would allow, and he published this in an engineering journal. Of course Haus, being an engineer, spotted that. I think I didnít see it till he pointed it out to me. Oliver had clearly made an oversight, because in stating that there would be less noise, he had assumed the phase of the signal was known. The phase of the signal is one of the unknowns if youíre trying to detect the signal, and so that if the signalís pulse is known that already represents partial knowledge of the signal and naturally the subsequent detection is easier and less noisy. So Haus and I wrote this up and tried to gently point that out, and I think thatís the only thing I published with Haus, although I saw a good deal of him. With Javan, from the beginning we had expected to do some things together, and we did. We were clearly quite close for some time. I was interested in a relativity experiment. It was a follow-on from the relativity experiment I had done at IBM, and Javan was also interested, and so we worked together. I also had a few postdoctoral people, Jaseja —

Bromberg:

You might like to just use this [bibliography] instead of my using itÖ

Townes:

Well, yes, letís see, this might help to remind me of the various people who were there. I see the very first paper was with Herman Haus and that was just clarifying this calculation of Barney Oliverís. Then, Carl Overhage who was at MIT was editing a book of lectures, one of which he had asked me to give. He wanted me to write it up, which I did. Then there was this work with Jaseja and Javan, using Javanís lasers. ďNuclei as Probes for Determination of Molecular Structure,Ē the next paper, was a hangover from work I had done some years before — just a kind of review paper. Then I guess I got going — I remember now — on the coherently driven molecular vibrations. There was a paper of Terhune and other people from Ford, that reported fascinating results about scattering of intense laser light, with frequency shifts, and I remember figuring out what was going on during an airplane flight. It was written up with Pandarese and Garmire. Pandarese was a visiting Italian student, and he wanted to work with me. Garmire wanted to do a PhD thesis. So this was something for them to start doing and we wrote it up. Next on the list I see a paper with Ron Malt. He was a doctor interested in lasers, who came around to talk to me about it, and I explained to him what kinds of things could and couldnít be done. He wanted very much for me to help him out and collaborate on this paper on optical masers in biology and medicine. For me that paper was also just accidental, because he was interested, and I was not uninterested. And there was the special test of relativity, then work on stimulated Brillouin scattering —

Bromberg:

Well, Iíd really like to ask a little bit about that whole thing, because that was a pretty major block of work there. One thing that struck me is this question that I put down there, under number 1, I read a speech, a report of a speech to Lincoln Labs in which you were talking about your interest in acoustic vibrations in connection with optical communications through the atmosphere, and of course I was wondering then from that whether that was related in any way to the nonólinear investigations that you were beginning about the same time.

Townes:

I donít at the moment remember, I have to think about that. I was interested in the propagation of lasers through the atmosphere. Iím sure I recognized that there would be acoustic effects. But I donít remember working specifically on that now. I remember working on propagation through the atmosphere. What year was that?

Bromberg:

Ď62.

Townes:

Ď62. That was prior to the Brillouin scattering. I think it had no logical connection in my mind at the time. I think that Ď62 work, that may have been a carryover from some of my considerations in Washington, because the Brillouin scattering really came about as a result, I think, of understanding of the coherently driven molecular vibrations. The Brillouin scattering is just a lower frequency vibration in a crystal, and I think thatís how we got onto it. I could look through my notebooks probably and figure this out a little more clearly as to just how that got started, but probably it had something to do with heating or possibly with self-trapping effects, and hence problems with maintaining a good beam in the atmosphere.

Bromberg:

— itís along the same lines but the applications, there are some applications to high frequency acoustic waves and so, also Iím asking whether the whole context, the study of high frequency acoustic waves was prior to this other?

Townes:

No, I believe it was subsequent. I was not particularly interested in high frequency acoustic waves. I was not uninterested, but itís not something I would have done research on per se. It really came from considering non-linear optics. Once I started looking at non-linear optics, I realized how many instabilities there could be, and all the different kinds of instabilities that transfer energy back and forth, became of interest to me. Now, when that occurred exactly, I canít say without checking. Clearly by the time I was working on the coherently driven molecular vibrations, it had occurred, and I remember very well thinking then of the whole thing in terms essentially of deviations from thermal equilibrium and how you arrive at thermal equilibrium between a very intense laser wave and all the other modes of a system. Such equilibrium you might think would normally occur slowly, but in fact, these instabilities made it occur very rapidly for certain modes. That is, there is very rapid transfer of energy from an intense optical wave, which is effectively at very high temperature to any medium itís traveling through which is effectively at a much lower temperature, and so this is really a problem of thermal equilibrium. I was looking at it that way, recognizing that then itís a question of which modes of a system will couple to the optical wave. And whenever there was a coupling, then there was likely to be a very rapid amplification and build-up of those modes. When I first thought in those terms isnít clear to me, but it was certainly by the time I was working on the coherently driven molecular vibrations. And it may well have been that work that brought this out, and the stimulated Brillouin scattering was also certainly a kind of an extension of that effect. Now, what I donít remember very clearly, Chiao or Stoicheff may remember better, and I could probably find it in my notebooks, exactly how we got started on Brillouin scattering in particular. I think I began playing around with just the possibility of coupling to Brillouin, because that seemed interesting kind of non-linearity. It was closely associated with the trapping phenomenon too, that involves a compression of material, and the self-trapping may have come first, before we did Brillouin scattering, but I donít remember.

Bromberg:

In the papers I think the self-trapping comes afterwards.

Townes:

I know on the time scale of publication, it comes after. But Iím not sure at this point which ideas came first, you see. Iím just not certain. Theyíre very similar. But I remember playing around with Brillouin and thinking that it has to be pretty strongly coupled, and that really it is a form of non-linearity in the index of refraction, and hence we should be looked at. But I canít tell you at the moment in detail just how that work was initiated. Stoicheff had done work on Brillouin scattering, in Canada as I remember, without non-linear effects, just normal Brillouin scattering. He had done a lot of Raman work in any case and I think he had probably worked on Brillouin scattering. Heíd certainly done a lot of very good high resolution Raman work, which is just the kind of thing thatís needed for Brillouin scattering, and it may have been when he arrived that we got particularly interested in that. But at the moment I donít know. I think Chiao and Stoicheff would at this point probably remember in more detail. Otherwise Iíd have to look at my notebook and see what I was doing and that would remind me.

Bromberg:

Iíll ask them and Iíll also see what I see in the records.

Townes:

Now, the self-trapping, as I remember I started worrying about that and recognized that there would be self-trapping.

Bromberg:

Now, in the paper[1] itself you speak about observations in a paper by a man named [Michael] Hercher who saw long lines of laser damage, and interpreted them in a way which you thought was not correct. Of course, again the question occurred to me whether an incorrect analysis of that problem was a stimulus to reading the literature.

Townes:

Yes, well, it usually would be. It usually would be. If I see some paper thatís been published and I think it isnít right, if itís important enough, I try to figure out what is right, and so thatís possible. I donít remember that paper by Hercher right now. I should look that up and see. There were damage effects in solid materials and so on which we looked at and worked on a good deal. My impression at the moment is that the ideas about self- trapping came before we knew about these damage effects, but I may be wrong. Iíd have to think about that more carefully and look at the record. I do remember getting the idea that self-trapping would occur, and then it was Chiao who primarily worked out the mathematics and both Garmire and Chiao, and I to some extent, did the experimental work on things associated with this. Chiao solved the mathematical problem in a precise way. Now, letís see, if we go on from there, I see thereís the Enrico Fermi school —

Bromberg:

Well, letís see — yes, that was the paper[2] on the same subject, and then another question that I have in here is, here you are at MIT and Bloembergen is a couple of miles away, if that much, at Harvard. The non-linear work that you were doing and his group was doing seem to me to be quite different in its character and its focus.

Townes:

— well, not so different, actually. Not so different initially. Initially we were presumably looking at the same problem. But what happened, as I remember, was that we published the paper with Pandarese and Garmire. Then Bloembergen took exception to it and felt that it wasnít right, so he published an alternate way of describing it. It was really equivalent in all ways although he didnít agree it was equivalent initially, I donít think. It was equivalent except the explanation about the directivity of certain beams, and there he had an alternate explanation which I think is not correct, but that was a minor part of his work. Bloembergen put it in a more abstract mathematical framework, is what he did, but it was essentially the same thing. There was more apparent disagreement than real disagreement. For example, I remember talking with him. He made a point that — let me see now — Iíd have to review this paper, but there was a certain condition under which the increase in the wave went linearly for a distance rather than exponentially. I think it was right on resonance, and Bloembergen insisted that that was not amplification. I had called it amplification. He insisted it wasnít amplification. That was a completely trivial point, really, because I think I use the language correctly, and amplification is any increase in power. But he thought amplification had to be exponential.

Bromberg:

This paper — thatís the paper on Brillouin scattering?

Townes:

No, thatís the paper on molecular vibrations. [3] Thatís where we first started doing similar things. Letís see, his paper[4] was with Shen, Shen and Bloembergen. Chiao and Garmire and I were doing things rather similar to what he and Shen were doing, but he was doing it a different way and I think there was an unnecessary amount of apparent disagreement, really. They were primarily just alternate treatments, but ours was first. His was rather more mathematically polished, and less physical. However these were essentially just alternate methods of looking at it, and he was using different terminology. Now, after that —

Bromberg:

Did you see each other? Was this a lot of communication by seminars and things between Harvard and MIT?

Townes:

There were some seminars back and forth, yes, but not that much. I was terribly busy at MIT and I saw my own people, and I think they may have talked with Bloembergenís group more than I did. I saw him occasionally. I remember arguing with him about this particular paper.

Bromberg:

I guess what really impressed me, and of course this is from a very naive viewpoint, is that Bloembergenís papers were very much more formal and concentrated on the light waves that were coming in and going out, whereas your papers were so heavily in terms of the molecules that you got the feeling you were walking around among these molecules and seeing what they were doing.

Townes:

Yes, I think that is correct. He tended more to mathematical formalism. And I tended more to physical insight and mechanisms. But except for some detailed paints both were perfectly valid ways of doing things. I remember talking with him. I went over to Harvard to see him and said, ďLook, Nico, we published and then you published a paper essentially saying that we were wrong and this was the right way to do it. However, look, hereís some things you said that clearly are not right,Ē and he had to agree with me. I said, ďYou know, I could publish another paper saying that youíre all wrong, but Iím not going to do that. I think thatís a silly kind of an argument.Ē He thanked me. And we were reasonably friendly, but there was obviously strong rivalry there for a little while, and then, after that, our scientific paths diverged. I just didnít have any taste for that kind of rivalry, for one thing. Secondly, I think our natural scientific tastes were different. He continued doing things a bit similar to that, and I thought since he was doing that, why cause friction about it? But it was not completely an overt decision, my own work also rather naturally diverged. So then I would see him regularly and weíd have some good discussions. I guess whenever I gave a substantial talk at MIT, he would come over, and I probably didnít get over to Harvard quite so much, because my time was a little restricted. But if there was a public talk announced that I would give or one of our groups would give, the Harvard group would come over. Otherwise weíd see each other every once in a while and discuss what was going on.

Bromberg:

What about the Lincoln people? This is just to get an idea of what the universe around you was like during the non-linear work. Kelley, for example.

Townes:

Yes. Well, Kelley I saw a lot of. Kelley came in to MIT. He would sort of come in and visit regularly and give a talk, and listen in on informal discussions and so on. I would say, with Kelley — Kelley we saw a great deal of. And I guess we published some with him, didnít we?

Bromberg:

Yes, there is — I think maybe on the next page of the bibliography.

Townes:

We were rather close to Kelley. I met him first at MIT at some talk, as I remember. He was around frequently, and there was not all that much work going on out at Lincoln Laboratory that was of a similar character which was interesting to him. Whereas Nico had his own laboratory and was doing his own things, there wasnít quite so much reason for him to come over. However, in Kelleyís case I guess, he got a lot of his experimental information and discussions from us, and then did the theoretical work so there was quite a strong interaction with us. There was also Perry Miles. Perry Miles was a young engineer in the engineering department, and I was asked to run a session at the Enrico Fermi Summer School, which I agreed to do. However in order to lighten my load, I got Perry Miles to be involved, and Perry was glad to do it because he was working on lasers and it was a good opportunity for him to play an important roles. Thatís how I got involved with him, specifically to help out on the Enrico Fermi School, and we then edited the resulting book together.

Bromberg:

Anything about that school that we should talk about? Was anything going on there that was singular, or any interactions with people that had an effect on the subsequent history?

Townes:

Well, there were a lot of good people there. Nico Bloembergen was there, and I enjoy seeing him. We had very useful discussions. Willis Lamb was there, and Willis is always a good person to talk with. Although heís not so voluble heís generally very sharp. A lot of good people were there. Iíve forgotten the list. One could look it up. It was a very good summer session, and we had very good discussions. The field was bubbling along pretty fast then. If you ask, was there anything specific that came specifically out of that, perhaps not. I think there were lots of small things and lots of interactions of ideas. I donít know of any one specific thing. At least, I donít think of any at the moment, but it was a very fruitful session.

Bromberg:

Did you have any Soviets at that school, by the way?

Townes:

Yes, Iím sure we did. Iím sure we must have.

Bromberg:

I was just wondering. There was some research going on apparently in the Soviet Union. Talanov is a name that I have heard. Iím wondering if that was of any interest.

Townes:

Well, Talanovís name I donít happen to remember, but, we can find out. We can find out who was thereÖ Let me ask — these tapes, now — can we consider them confidential? I donít mean classified, I just mean confidential. Well, the reason I want some restriction on this, I donít mind your using them or any historian using them, but I would like to be able to insist on leaving out some parts, because there are of course personal things here that I think may be put in a very poor way and could seem contentious or hurt some people. I donít think thereís very much but there might be a little, and I would like to be sure. OK, what questions do you have?

Bromberg:

Well, I wanted to know about the attitudes that IDA had, and DOD, towards the development of lasers, and what actually happened, key events, and I think it would be good to get a little feeling of the relation between lasers and the context of what you were doing generally, to get some perspective on it.

Townes:

Well, if you refer to Columbia University where I was when I went to IDA, I had a fairly big laboratory at the time. I must have had eight or ten students, and doing a variety of things. Trying to build a laser was one of them, and also radio astronomy was another project that I was working on, and then various other aspects of radio and microwave spectroscopy. I must have had something like ten students. At the time I had at least one more scheme, probably, several, for trying to make very short waves, that I was working on. I think the Cerenkov radiation work was going on at the same time. So I was very busy, but I felt pretty strongly about the importance of scientists in government and the so-called space and missile gap during that period. There were very few scientists in Washington at that time, really. And so, when I was approached to take this job at IDA, which seemed like a fairly critical job, I just felt obligated to do it. It was difficult because I had to leave a lot of students there, — but they agreed to pay my transportation back to Columbia on the weekends so I could work on Saturday and see my students.

Bromberg:

How did they define that job?

Townes:

mp3I was vice president and director of research at the Institute for Defense Analysis. T he president was more or less a businessman, so I had the primary technical responsibility and the whole job was mostly technical. He was even more of a contact man with politicians and government officials. Most of the running of IDA really fell on me. I also hated to drop out of the laser work, but I felt it was just terribly important for some scientists to go to Washington so I did it. As a matter of fact, I remember Walter Brattain was urging me, "Oh, donít do that, you must build a laser," thatís the most important thing, to build a laser, because it was of Nobel prize importance. Both he and I knew one or two people that had already nominated me for a Nobel Prize, and he kept saying, "Thatís the thing you must do." I felt the laser was really in the bag. It obviously could be built and it just wasnít critical for me in particular to build one. I would have liked to build one, first, but I felt there were more important things to do and if the Nobel Committee didnít understand that the critical work was really all done, it was just too bad. I had been nominated, I know, on the basis of the maser already, and wasnít all that worried about it. The Nobel Prize does mean something to scientists, and so I thought about it seriously, but decided that I really ought to go to Washington. However, that was something of a shock to my students.

Bromberg:

That was Abella and Cummins who were working on the —

Townes:

Abella and Cummins were working on the laser. But then I had about six or eight other students, you see, that were in the middle of things, and it was something of a shock to them. But they took it fairly well. I came up on Saturdays to try to help them out. Now, in Washington, the primary role of IDA at that time was to provide the technical advice for the Weapons Systems Evaluation Group, and also the technical advice for what was then ARPA and is now DARPA. Thatís the Advanced Research Projects Agency in the Pentagon that supported most of the innovative work. Then I was fairly close to the Presidentís Science Advisory Committee, and was a consultant there, and then we were doing some things for the State Department. The work involved a wide variety of sort technical evaluations and advice to government, and IDA was a key agency at that time. I think now itís doing an important job but is not such a critical one. It was ARPA in particular that was interested lasers. It was their natural function to develop lasers. Thatís new technology. And ARPA was interested. They had a good deal of money at the time. In fact, money was fairly abundant to try almost anything. They were looking for places to put their money. It was just one of those periods in which there was great expansion and ARPA really had no good place to put a lot of their money and were putting it on a lot of very chancy things. It was a good time for new technology from that point of view. The laser was something that was obviously interesting to them. It didnít develop very rapidly, and I think the military had moments of considerable doubt and then moments of considerable hope. We did some analysis of the laser for military purposes and some discussions of what its limitations and possibilities were. There was Bill Culver and then Bob Collins who I got to come to IDA. Bill Culver had been at Rand and become interested in lasers there. I had known Collins when he was at Bell Labs. Later he went to Minnesota, I think, and I got him to come to IDA from Minnesota.

Bromberg:

Now, he worked with Schawlow and the rest on the laser right in the middle of 1960.

Townes:

Yes, somewhere in there.

Bromberg:

So he must have before that?

Townes:

No, he came shortly after that. I think he came shortly after that. So he was there in Ď60 or Ď61, probably Ď61 he came.

Bromberg:

Did you set up a separate laser group?

Townes:

They didnít have a separate laser group, no. The organization simply didnít go that way. Lasers werenít that big an item. We had various sorts of people who were working on lasers. I had almost forgotten that Bill Culver was in IDA for a while.

Bromberg:

He was at IDA for a while.

Townes:

OK, I remember talking with him a good deal at that period. It was quite early that he was involved. Then, I got Collins to come down. Now, Collins was rather skeptical of the laser ever being a military weapon. I was somewhat skeptical but felt that there was a possibility and one ought to try pretty hard to look at it. Collins worked on it and tried to sponsor research, but he was generally skeptical of its ever working as a weapon. Culver was very optimistic about its working as a weapon. He was always very enthusiastic about the great things that the laser was going to do for military technology.

Bromberg:

Was this an anti-ballistic missile or personnel weapon or?

Townes:

Anti-ballistic missile success was the big thing to try for, and itís in that sense that I mean there was skepticism about the laser working. I was skeptical myself but I felt that it was important to work hard on it to see what could be done, because theoretically it was possible. Bob was rather more negative and Culver was much more positive.

Bromberg:

In ARPA itself what was the reaction?

Townes:

Well, they were interested. They were interested in it as a fascinating new technology. A few people were very enthusiastic and other people were pretty skeptical, but it was just the kind of thing for that time and for the large amount of money they had. They had lots of money. They were eager to do some new things. It was partly for that reason that we were given the go-ahead to do new military technology with lasers. It was a bright new area, and as I say ARPA had almost more money than it knew what to do with, so lasers were well backed.

Bromberg:

Some names Iíve heard, I just want to query you on them — Paul Adams and somehow Robert Kingston is getting into the act.

Townes:

Bob Kingston? Well now, Bob Kingston, I think, was at Lincoln Laboratory by then. Bob Kingston was interested. I think Bob Kingston had been involved in the maser amplifier at Lincoln Laboratory.

Bromberg:

He was involved on some sort of DOD committee.

Townes:

Yes, thatís true. Thatís true. There were a number of committees around, to study the problem, and I was involved with those and they interacted with IDA some. I was not on some of the committees, just because of my position at IDA, but I was in close contact with most of those committees. Letís see, thatís right, Bob Kingston I think headed some committee for that.

Bromberg:

That was early Ď62, there was this report that the Kingston Committee was set up to advise, and another report Iíve heard anecdotally is about a very important meeting that took place the end of Ď61 or thereabouts in which a group of scientists were called together, and Bloembergen was one of them, and they were to decide on the practicality of a laser weapon. Now, whether this had anything to do with the Kingston group or whether it actually occurred Ė-

Townes:

I think all of these things were somewhat later. They were somewhat late compared to what Iím talking about. I was not on the Kingston Committee. I had a little interaction with them. There was however a DOD special committee and Bloembergen was on that. That was probably towards the latter part of my time at IDA or a little bit later, possibly shortly after Iíd left IDA, but maybe toward the latter part of my time at IDA. By then there was a good deal of laser work, sponsored by ARPA, and they wanted advice from a group of physicists. I may even have helped organize that committee, that is picked out the people. In any case, there was such a committee to advise ARPA, which was not directly a part of IDA. Bloembergen was on that. As I remember he started out rather skeptical and then suddenly became rather enthusiastic. And as I remember, his enthusiasm came about from a calculation about how much energy can be stored in a crystal with a certain number of atoms excited. Well, thereís lots of energy there, thereís no doubt, and he realized that, and as I remember, gave quite a pep talk to the group about the possibilities. People certainly felt that work ought to continue and there might be some real chance of success. Now, I donít remember exactly what year that was, but I would suppose possibly late Ď61 or early Ď62. I remember also talking with Gene (Eugene) Fubini. He was present when I gave a talk to a classified group in the Pentagon, mainly Pentagon officials, weapons systems people, and others closely connected with the Pentagon, about the possibility of lasers. They had asked for such a talk. And I remember very well a question from Gene Fubini who said, ďWell, but these lasers all have efficiencies of 10-3 or 10-4. That seems to be inherent. None of them have been better than that, and we canít possibly think about making a weapon with that kind of inefficiency.Ē I remember pointing out to him that thereís nothing fundamental about such inefficiency. I saw no reason why a laser couldnít be as efficient as any other energy conversion device, namely maybe up to about 50 percent, and certainly some tens of percent. We just had to find the right way of doing it. After that, Fubini seemed convinced that there was a possibility. I think most people like myself had serious doubts, but then on the other hand, the possibilities were interesting enough that I felt we should give it a good try. One couldnít either rule it out or rule it in. It ought to be tried, and in any case the technology was interesting. It would be useful for something. We could think of many varieties of things for which it would be useful in any case. Whether it would ever become an anti-ballistic missile system, I think was pretty iffy in the minds of most people, except a few enthusiasts.

Bromberg:

On the technical issues, the efficiency was apparently one, and the question of whether you could get sufficient power out was another. Are there other technical questions that were important?

Townes:

Well, the question of directivity. Now, another technical issue on which we worked a great deal was the question of propagation through the atmosphere. That came a little bit later, though.

Bromberg:

So you continued to be affiliated with all this when you were at MIT, it sounds like.

Townes:

Well, I was slightly, but I was very busy with administrative work at MIT. I was also doing [research] again. I took one day a week for research, and since I was right there at MIT I didnít have the traveling I had when I went from Washington to Columbia on Saturdays, I could talk with my associates there, and directly supervised about one postdoctoral person and two students. I limited myself to that. Ray Chiao was one of the students, and Stoicheff was working with me then. He came as a sort of sabbatical visitor. So I kept up with things to some extent and worked in the lab some, but it was a very part time thing. I was so busy that I tried to keep out of Washington, but when things that were very close to my own interests, I participated, in Washington discussions. Iím trying to remember the sequence of events. You see, this is an aspect I havenít thought about a while. Keith Brueckner replaced me at IDA. I had also, while I was at IDA, organized something called the Jason group. The Jason group was a group of about 25 of the countryís really best physicists Ė- the best young physicists in the 30 to 40 years age group. It was headed by Murph Goldberger who is now president of Cal Tech. Keith Brueckner was in it and Murray Gellman, and really many of the best and most active young physicists of that period. The idea was to get some new blood into the thinking in Washington and some new people educated about national problems.

Bromberg:

I see, the old group was the Los Alamos crowd, the Radiation Lab?

Townes:

Well, yes, it was in a sense a replacement for the Radiation Laboratory crowd. I felt that the older group was getting pretty old and eventually there wouldnít be anybody around who was knowledgeable about governmental problems, and that there must be new people educated.

Bromberg:

Why did you call it Jason?

Townes:

Well, that was an invention of Murph Goldbergerís wife, Mildred Goldberger. It didnít make any difference to me what it was called. Mainly I wanted to get them going and participating. And so when Murphís wife came up with that name, and he liked it and other people liked it, I said, ďFine.Ē I think she had the idea of the Golden Fleece or something, but Iím not sure Jason was all that admirable a character, actually. Anyhow, it was she who picked it and I was happy to agree. That was organized along about in Ď60, I guess, and it took some time to get these people briefed adequately and oriented in some of these problems. They worked on lasers some. Keith Brueckner was one of the people who worked on atmospheric propagation, but here Iím a little fuzzy about the time. Iíd have to think about it some. Ray Chiao and Elsa Garmire and I had done work on self-focusing due to non-linearities. That clearly was after I went to MIT! I donít remember now what year but probably Ď62.

Bromberg:

They probably started in Ď62.

Townes:

Probably about Ď62, and I think it was that that made me realize that one could also get thermal blooming. So that the non-linearities, in the case of the atmosphere, would go mostly in the other direction and tend to spread the beam out. I might possibly have realized that before, but I donít think so. I think that came along because of the trapping and focusing idea. But I did of course know about absorption in the atmosphere and various things like this. Brueckner worked on absorption some, and then together with that on thermal blooming, and he and I had some big arguments. I maintained he just didnít understand molecular absorption, which he didnít. Somehow he wanted to assume that absorption in molecules was exactly like the absorption in water droplets, which is a very different problem. The spectrum of water droplets is very smeared out. Bruecknerís an excellent theoretical physicist; he just hadnít worked with molecules. I remember terrible arguments about that. He insisted on writing a paper on it. I knew it was absolutely wrong. But anyhow, that was just one of the scuffles in trying to get things sorted out, when we were working on propagation problems. That is a very serious technical problem, propagation through the atmosphere. Also to what extent laser energy is dissipated in clouds was a question I worked on. You can punch a hole in a cloud if you put enough energy in; you just evaporate the water. Iím sure I worked on that before I left IDA, that is, the possibility of penetrating clouds. Yes, it comes back now. That came up before the thermal blooming, the possibility of penetrating clouds, and I guess Keith was arguing, even after you evaporated the water, it would absorb the same amount, which anybody in the field of molecular spectra knows isnít rights.

Bromberg:

Now, space stations were already being talked about in the literature.

Townes:

Yes.

Bromberg:

Was that something that you were already concerned about?

Townes:

Oh yes, space stations were being talked about, sure.

Bromberg:

I mean for lasers, lasers in space? You read that in ELECTRONICS or AVIATION WEEK.

Townes:

Well, that was pretty vague at that time. It was hard enough to build lasers of enough power, and we were trying to get them through the atmosphere mainly. We realized that if you couldnít get them through the atmosphere, of course, you could put them into space, but as I remember that was not a very serious proposition at that time. Space activities were very hot then, and everybody was interested in space, but it seemed pretty difficult and lasers themselves seemed pretty difficult, so that not very many people really urged that the two should go together. It would be a double difficulty. Another thing I worked on at that time, was with somebody from Weapons Systems Evaluation Group, because I wanted to get those people a little more current in modern science and in contact with the scientific community more, instead of just buried in the Pentagon. A man named Schwartz with whom I wrote a paper on communicating with extraterrestrial intelligence by laser beams — I guess Morrison and Cocconiís paper had just come out. They felt such communication ought to be done at the 21 centimeter line. I think they just didnít consider lasers, and so we wrote a paper pointing out you could also do it with lasers, and there was no good reason another civilization would necessarily choose the 21 centimeter line. That I know was during the time I was at IDA. Now, let me say that lasers at that time were really a minor part of my total activity, however. It was something that I was involved in technically and worked on from time to time because I was knowledgeable about them. But that was not the primary point of my going to Washington at all. It was for rather more general advice in a very wide variety of fields, and I was mostly doing that, so the lasers were a side issue. Actually getting this Jason group going was a very much bigger occupation of mine, and they worked on a very wide variety of problems. Lasers being only one of them. OK, well, maybe weíve talked enough about that, unless you have something else.

Bromberg:

I just have a very few small points to clear up. Before the actual laser, there was of course the TRG contract. Were there contracts with Westinghouse or Bell or something else that I ought to be looking for?

Townes:

I donít know. Iím sure there were other contracts, but I canít name them at the moment. There was money for supportive work, so — other contracts — Bell Laboratories at that time didnít want classified work, so they wouldnít have had a contract. I suspect Hughes probably had a contract. I suspect various aerospace companies that were interested in just studying the problem theoretically probably had contracts. I donít know how many other people had contracts in developing lasers, but there were likely a few. Actually, ARPA was advising and dispensing money on that, but I just donít happen to remember very much about what specifically was done. I was more looking at the theoretical and analytical possibilities, as to whether to support the work at all, and what directions it ought to go, rather than the contract part of it.

Bromberg:

Then someone named Paul Adams has surfaced in some other conversations. I just wanted to know —

Townes:

— I donít place Paul Adams. Who is he supposed to be?

Bromberg:

Heís supposed to have been in ARPA, maybe a lawyer or somebody, Lawrence Goldmuntz spoke to me about him being a real enthusiast within ARPA and somebody who promoted —

Townes:

— funny, I donít remember him. I just donít remember Paul Adams. Now, you know, maybe I knew him and Iíve just forgotten him. But I donít place him at the moment. He was supposed to be a lawyer, you say?

Bromberg:

That was my — I would have to check.

Townes:

Well, you see, there, that may be part of the reason that I donít remember him. I dealt mostly with the technical people, among the contracts people, some might have been very enthusiastic, but I wouldnít have had any dealings with them unless they came to me specifically to ask if something was feasible. Generally, they would get technical advice from our group. That advice would be in memoranda and so on. But the administrators might not actually have asked questions, and still have had strong feelings. Paul Adams might well have been a contracting officer or something like that and very enthusiastic. But if he was there, the chances are I saw him. But I donít remember him, in any case. Since I havenít reviewed any new notes or notebooks about the period you have just been asking about, I am rather uncertain about some details and timing. For precision, I should really look over written material in order to be more precise.

Bromberg:

The other thing that I put down in this group [of questions] was, whether the work you were doing at IDA had any reaction back on your research afterwards? Whether you took any problems that really influenced the direction of any research?

Townes:

No, not really. In the first place, I went into an administrative job at MIT. The research I could do was really quite limited. Of course, I worked on lasers when I went back to MIT. But it was very different from analyzing the military possibilities of lasers, and while I kept in some contact to help out in the national laser program, I didnít myself work on any lasers particularly applicable to military things when I went to MIT.

[1]R.Y. Chiao, E. Garmire, and C.H. Townes, "Self-Trapping of Optical Beams" Phys. Rev. Letters 13 (1964) 479-482.

[2]R.Y. Chiao, and E. Garmire, and C.H. Townes, "Raman and Phonon Masers," in P.A. Miles and C.H. Townes, eds. Quantum Electronics and Coherent Light, Proc. of the Int'l School of Physics "Enrico Fermi," 1964, pp. 326-338.

[3]E. Garmire, F. Panderese, and C.H. Townes, "Coherently Driven Molecular Vibrations and Light Modulation." Phys. Rev. Letters 11 (1963), 160-163.

[4]Y.R. Shen and N. Bloembergen, "Theory of Stimulated Brillouin and Raman Scattering," Phys. Review 137 (1965), A1787-A1805.

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