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In footnotes or endnotes please cite AIP interviews like this:
Interview of Willis Lamb by Joan Bromberg on 1985 March 7,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Some of the topics discussed include: the development of his career along with the problems of the simultaneous development of his wife Ursula Lamb's career in academia; radiation; megnetron oscillators; laser theory; quantum theory of lasers; government funding of research. Some of his associates mentioned are: Arnold Nordsieck, George Uhlenbeck, Van der Pol, Charles Townes, Leonel Menegozzi, William Wing, Marlan Scully, E. T. James, William Bennett, Richard Fork, Sargent, among others.
Shall I read the first question out loud?
Well, the questions will go in as part of the record… I’m talking to Professor Willis Lamb in Tucson. Yes, you can read the questions or you can just answer them if you like, because as I say those questions will go into the file. And.
This question expresses an interest about what I was doing from ‘43 to ‘4 that had a connection with oscillator theory. Well, starting in November of ‘43 I began working in the Columbia Radiation Laboratory at Columbia University on magnetron oscillators, and these devices were capable of oscillating, generating highly monochromatic radiation, but sometimes in several different modes of oscillation, and for various reasons, that were well known in the radar field, which was very undesirable. It was much better to have the oscillation in one mode, and one of the questions that I tried to do something with was to understand the theoretical basis of this behavior, and if possible find some way to prevent the oscillation in a number of modes. And in some way or another, I did learn from some papers by the Dutch physicist (B.) Van der Pol.
I wonder if you have any recollection of how you came across those, since I don’t think the average physicist was reading those at the time?
Well, it was in the PHILOSOPHICAL MAGAZINE in 1920, ‘22, and I really don’t remember how I learned about them, but there were two physicists that I knew quite well, and maybe one or the other gave me some clue which led to finding out about this work. One of them would have been George Uhlenbeck, but I don’t think he knew Van der Pol. Actually, at some time or another I had actually heard Van der Pol talk. This was probably at some seminar at Cal Tech in the late thirties. The other physicist who knew of things that were very useful to me was Arnold Nordsieck. He was a colleague, I’d known him when he was a student at Berkeley. He was several years ahead of me, and we both got to be instructors at Columbia, starting around 1938 or so. And he knew a great deal about nonlinear mechanics. But I can’t really say for sure how I came on the Van der Pol papers. It may have been some reference to Appleton, because one of Van der Pol’s papers was co-authored with Appleton.
You were talking with Uhlenbeck and Nordsieck even in the period when you were working on magnetrons? That was part of your intellectual —?
In ‘43 I had been going on five years at Columbia. Nordsieck came about the time I did, a year earlier, maybe, and at some point during the war he moved from Columbia to Bell Labs, but we were still very close together. Uhlenbeck spent a year or a good part of a year at Columbia some time during my Columbia period, which extended over a period of 14 years altogether.
Bell Labs was down at West Street then, they were in New Jersey?
Well, Bell Labs was at West Street, until I think the mid- or late fifties, probably.
So that would be the whole Columbia period. You’d really be able to —
I don’t think they were at Murray Hill. I think it was West Street. I’m a little — I’m unable to say how I really got the specific reference to the PHILOSOPHICAL MAGAZINE and Van der Pol.
It sounds to me as if my premise is wrong. My premise was that physicists were not very well acquainted with that work, but everything you say sounds as if this was quite part of the normal information physicists would have.
No. No, it wasn’t. No, it wasn’t. The mechanics that I learned had nothing about such things. Of course, the problem of planetary motions was a problem in nonlinear mechanics. The simple pendulum with a large amplitude of awing is a problem in nonlinear mechanics. But in general physicists only were interested in the problems they could solve analytically, and you could quickly get into elliptic functions with some of these problems in which you couldn’t go further. So except for those obvious problems in nonlinear mechanics, that are in all the textbooks, physicists know very little. Now, there were some exceptions. Arnold Nordsieck was an exception. And we had had around 1940 an experience that is relevant to all this. The work on the Manhattan Project that occurred in the Pupin Laboratories at Columbia started some time in 1940, and it was classified and parts of the building were devoted to it, and I was not able to really have much to do with what went on there. But one day Nordsieck came and told me that he had been approached by either Dunning or (Eugene) Booth about a problem in mechanics that they had.
It was the problem of the pump, and the pump as it was described to me consisted of a cylinder sealed somehow at both ends and with another cylinder inside that could move back and forth inside the first cylinder. And the outer cylinder was to be shaken, and thereby the inner cylinder which was more or less free to move would move, and then in the spaces between the inner cylinder and the outer cylinder, there were some valves placed, so that whatever gasses were in the two ends could somehow be pushed in and out through the valves. Well, taking what I now know, this was probably some device that was being considered for pumping uranium hexafluoride, and — but none of this was disclosed at the time. Anyway, the equations of motion for that device depended upon knowing something about how the pressure and volume and temperature were related in a gas undergoing adiabatic expansion, and as the plunger inside the cylinder moved back and forth, it compressed and decompressed the gasses and they went out through a valve which opened under certain conditions of pressure.
So one could easily write down the Newtonian equations of motion, with the motion of the plunger, because of the shaking and became of the gasses that were present in the chambers. And these equations were nonlinear because the motions were large amplitude and you couldn’t make them simple harmonic approximations by expanding something in a Taylor series, so the result of this was that you had a problem that you couldn’t solve analytically. And Nordsieck had a great interest in analogue computers, the differential analyzer that (Vannevar) Bush had worked on, and he knew that there was at the University of Pennsylvania in the electrical engineering department, Moore School, I guess it was called — that they had a differential analyzer, so Nordsieck thought I could be of some use, just to help with what had to be done to make the calculations, and so we must have made a dozen trips down to Philadelphia, and made calculations using the differential analyzer there. So that was the place where I really had some firsthand connection with nonlinear mechanics.
That’s interesting. It really is coming in with the very practical problems of the war.
Yes. Well, for my contribution to this work, I got a check for $75! At a time when Columbia was otherwise paying me $200 a month, so that was a substantial — but I never found out how useful the work was. It was useful to me, anyway. So when a couple of years later I learned about what Van der Pal had done, I could see that the same kind of dynamical problem was involved. I didn’t at that time have access to a differential analyzer. Now, the problem of a magnetron oscillator is enormously complicated. This may be more detail that you want, I don’t know that it’s — you can always cut it up.
Well, what I’d like — that’s right —
The way in which it is enormously complicated is something like this.
In fact I might put this on pause while you explain it… So then, the fact that you couldn’t handle the magnetron by the analytic techniques you had then, we’re talking about in the ‘43 to ‘45 period —
How did you work with it?
Well, I tried to handle it in the way that Van der Pol did, by replacing the cavity by something like the coupled inductance, and capacitance, and I tried to just describe the effect of the electron motion by introducing some effective voltage that was applied across such a circuit.
Now, at this point when you were actually working on radar, did you have any kind of computer facilities available to you?
I had a 12 inch circular slide rule. I had a Marchand electric calculator. There was at Columbia an astronomer named Wallace Eckhart, and he had, for many years, been doing punched card calculations of the orbit of the moon. But even though I knew Eckhart pretty well, I was really never at the point where I could find out what he was doing or how he did it, so — Anyway, I did succeed in more or less imitating the sort of thing that Van der Pol had done, except he was considering a triode oscillator, and I tried to make the modes of the magnetron correspond to a number of coupled triode oscillators. And it was suggestive, but it didn’t really do anything useful for the problem at hand. The thing that was most useful was invented by Nordsieck and (Sidney) Millman, who returned much later from Bell Labs, was to make these alternating resonators of different lengths, so the structure that was devised was called The Rising Sun structure because it had the rays of the light coming out of the sun were of different lengths, something like the Japanese flag was imagined to be, and what that did was to make the resonant modes of the empty cavity have a structure which was less prone to the multi-mode operation.
Now, at this point I jump to my questions, way over to Stanford. Is there something, here, you may want to put in something that you haven’t previously discussed which is relevant to the laser work, although your little article in the JOURNAL OF QUANTUM ELECTRONICS did have quite a bit of the background.
Stop a moment…So your second question is, “You have written of your own calculations on masers in the Stanford period and interaction (?) with who also supervised Maiman(?) and (?) and we would appreciate any other memories of maser research in those years at Stanford, or more generally in California, and the beginnings of the word on the two metal(?) maser make an impact on you? Harold Lyons’s laser group at Hughes and the interest of Hugh Heffner at Stanford Research Lab.”
Or other things that I don’t have any knowledge of.
Well, I think I told that in that article in JQE, pretty well. I left Columbia in ‘51, and the suggestion that he could make a maser interested me, but not in any active way, until the device worked in ‘54. And I had had a lot of experience with the two level atom, the problem of two levels, in the perturbing field, in connection with the hydrogen fine structure work, so it was fairly natural to try to teach myself what I should have realized earlier by trying to put together a theory of that device. Let’s see, I think we did leave some things out about the Columbia work, because you’ve certainly seen some reference to what I thought might happen in the hydrogen gas discharge, in the PHYSICAL REVIEW article on the hydrogen flash lecture.
I have not read all your articles. I’ve read only, well, examined only maybe 15 or 20. And I didn’t read the hydrogen fine structure article.
Do you want to ask enough so you’ll have —
Yes, I want to tell the tape recorder that I’m asking about the question on the impact of science on technology, that’s the name of that paper, my question 24, and I wonder to whom this discussion in this paper was addressed? Was it laser physicists or lay people, because it has a discussion of whether or not there are photons, what a photon means, what the relationship between the classical and the quantum theory should properly be. And it was really a question of how much your theory had diffused into the laser community in your eyes by that point, how much real understanding of yours and other people’s at this point.
I really don’t know very much about how much it diffused. I think the paper is well cited in the citation index, but that doesn’t mean very much. I went into a fair amount of detail about —
— I guess I’m curious as to why you chose those two topics to end up the paper with? Maybe that’s a better way of putting the question.
Well, the phenomenon of stimulated or induced emission is one that I think has confused a lot of physicists. Some would say Einstein was confused about it, and I can go over that in quite a bit of detail, but I think it’s spelled out here in this paper, in some ways, maybe not as sufficient.
Well, it’s not really necessary to go into that, I think. I think that’s in the record. As I said on our walk over here, we want to put in stuff that isn’t anywhere else, that people can’t read in your publications. Maybe we should go back then to the chronological order. Then we can get back to this as necessary. We were talking about the Columbia period, then.
Yes. Well, I was thinking about things that, if it had been somebody else, could have led to realizing that something like a laser could be made. I got as far as seeing that possibly microwaves would not be absorbed in a gas discharge, but would be — would have a negative absorption, and I did not realize that that was the same thing as having an amplifier. And that was the same thing as not realizing that you could have an oscillator.
In the JQE article, you intimated that you had been skeptical about the maser when you — is that it? Did I read that right? When Townes was first starting out to propose it.
Yes, well, he was going to use ammonia as the working substance, and I had certainly been thinking about what might happen in a hydrogen discharge, and since I hadn’t — it seemed to me that nothing much would happen in a hydrogen discharge. Certainly I didn’t see that one could make a substantial amount of micro wave radiation, if you had the conditions right. The hydrogen conditions were not right. It wasn’t the right material. You couldn’t get enough of it to do what you wanted to do. Actually, the ammonia beam laser isn’t a very powerful device either, but —
I’m assuming that this skepticism was expressed in actual conversations with Townes?
No, I don’t think it would be anything more than hearing about it, from him, possibly from him, I think so, and saying “It sounds hard” or something of that kind. I think I just would not have seen — I wouldn’t have seen the connection between what he was trying to do and what I was wanting to do. They’re obviously now closely related, but they weren’t at the time.
And when did you begin to see the connection?
After it worked.
I see. Do you have notebooks as far back as that period or any kind of papers?
In general, I work on small pieces of paper, which in due course get lost.
There is one exception to that. I was in Oxford from ‘56 to ‘62, and one year I was asked to be one of the examiners for the tripos examinations at Cambridge. I don’t know whether it was ‘58, ‘59 — yes, I do know — no, I don’t. It might have been ‘59 or ‘60. Yes, natural science tripos, part 1, 1959. Dated. And this object here is the place where you have the names of the students, and you’re supposed to put down marks on the examination, and each examiner was given a couple of such large books. Well, I managed to take care of my examining duties without using any of these books, but what I did have was an … (off tape) …(Question # 5) Well, you know, the corpuscular theory of light was the only theory of light that was taught in Cambridge, England, until 1945. The physicists of my generation may have known something about electromagnetic theory. They also knew about emission and absorption of light, and they tended to think of light as involving photons. And I had another experience that led me to look at things a little differently. During the war, I taught a lot of courses in, at Columbia, for the Navy V-12 candidates, something of the sort, so that I had that experience, a certain amount of what we call electrical engineering, and that had the — that had some influence. I think the confusion in people’s minds about the nature of the photon and the electromagnetic field, stimulated emission, is — the confusion is pretty widespread.
“Why did you decide to go to Yale? What role did your interaction with Bennett at Yale play in your development of laser theory? Have you always been in touch with him about his paper, this was ‘62, before you came?” Well, I think I went into as much detail as I could remember with Nancy Cartwright on that. What she wrote will have some things that… without any notes, without any documentation; there isn’t much documentation.
Unfortunately, I don’t think that this really lists them. If Nancy doesn’t have notes. Of course, some of it is in her paper and some of it is in your paper. We don’t want to talk about that, but I don’t think there is much in either her or your paper about why you actually went to Yale, and whether your interaction with Bennett played a particular role? Maybe it just didn’t play a particular role.
Well, I can answer that question. Why I went to Yale. Well, do you want to — the whole answer to that question of course would involve some other questions and answers, namely, why did I go to Stanford? Why did I go to Oxford?
OK, let’s do that.
You want all of that detail? It’s not… OK. Well, I’ll assume I got to Columbia. You don’t want me to explain why I went to Columbia? I got to Columbia because one summer at Stanford, I.I. Rabi, who was a visiting summer lecturer there, this was in ‘38, and he must have been favorably impressed because he wrote the chairman at Columbia, who was Dean Pegram, and got me an instructorship. A year later I married, and my wife and I lived quite near Columbia. She had, she was an historian, is an historian, and in due course got offered a part time teaching job at Barnard College, and the part time job was to give the lectures, the Saturday lectures that the head of the department did not wish to give because he lived in New Jersey. It wasn’t a matter of religion or anything, it was a matter of not wanting to come in from Leona, New Jersey, and she taught at Barnard until about the time we left there to go to Stanford.
She got a somewhat fuller teaching appointment at Barnard subsequently to the time she left the first appointment. But in about ‘51, it seems that she hadn’t pleased the dean very much, and her job was about to disappear. Well, I won’t go into the details about what might have been right or wrong about that. Suffice it to say that it became undesirable for me to stay at Columbia any longer, and I had a chance to go to Stanford. Now, there is an interesting story about that but it isn’t the story we’re pursuing now so I won’t, I’ll skip over the details. It seemed at an early stage that my wife could very possibly get a job at Stanford. At least the physics department thought it might be possible. But when they looked into the situation, they found that there was a very strong university rule against nepotism. So that without any need for the history department to consider the merits of the case, it was clear that it wasn’t going to be possible. Well, despite that, it seems that I had to leave Columbia. She was able to continue some kind of historical research, even when she was at Stanford. She was given facilities in the library to do that. She worked on some manuscripts of one of the close associates of Napoleon that had somehow found their way to San Francisco and were found in an attic. But it was also clear that there wasn’t going to be a teaching job, and no real contact with any professionals or with the members of the history department.
Then in ‘54, the fall, I was approached by some people at Oxford who were looking for a successor to the departed professor of theoretical physics there, and the gentleman who made this invitation thought that my wife might possibly get an association with one of the colleges and do some teaching. There wasn’t any firm promise of any appointment but he thought it would be possible, and he was, so to say, an operator, but a very nice person, and so it seemed an interesting thing to do, and so we did it. And when she was there, she did in fact get a very loose connection with some of the colleges. She did give university lectures and she did some examining. She did some tutoring. No real connection, but she also found some manuscripts in the Bodleian Library that had been, hadn’t been discovered previously until, ever since about 1870 or so — as they weren’t completely new but they hadn’t been written up, had not been noticed for a long time. Anyway, that directed her into a new kind of research, namely, of what sometimes would be called cosmographers, the pseudoscience of navigation in Spain about the time of Columbus and later. Well, in — one of the factors that took me to Oxford was the repugnance with what had happened during the McCarthy years. I wasn’t in any trouble, but I didn’t like what was going on. By ‘62, it seemed that I might go back again, and I had a chance to go to several places, and I picked New Haven because it seemed to me that it was one of the most backward cities in America, and that would make it easier to use for a transition. A transition from England back to America would be easiest if we went to a city that was almost as backward.
Are you talking now socially? Not in terms of physics?
No, I’m not talking about physics, I’m talking about the environment. Yale has buildings that look like Oxford colleges. But they don’t act like Oxford colleges. They haven’t the least idea of what an Oxford college would do. That’s only —
But there must also have been professional reasons.
Yes, surely. I had a very good friend, Vernon Hughes, one of my longstanding and very good friends. It was his idea that I should go, and he was aware of Ursula’s problems and thought that he could persuade the Yale authorities to do something about it, and in fact, they did. She was appointed a research associate in history, and in due course they appointed her a lecturer in history. They made her a fellow of Helen Hadley Hall, the women’s college at the time. It wasn’t a women’s college but it was the nearest they came. She was then made a senior lecturer and then she was made a continuing lecturer, in some order, I can’t remember which comes first, but she was never made a professor. The history department had a hundred faculty members and she was the only woman. It was a very disagreeable experience as far as —
Unbelievable and this was in the sixties!
Well, if I go any further I’ll be getting up to the reasons why we might have left Yale, but —
Well, we’ve got you in Yale so let’s stay there for a little.
Stay here... When you interview old people like me, you see that we can’t remember what we’re supposed to remember! But only about what happened when we stole a spoon in San Diego.
I think that’s — well, I won’t say anything.
Let me just finish this part. During the time she was at Yale, she got a Guggenheim Fellowship. She got a grant from the National Endowment, a senior research grant from the National Endowment for Humanities. She had some very good students who got their degrees with her. But no promotion. In ‘71 or so they had a terrible financial problem, and they decided to tell her that her continuing lectureship would expire at the end of three years. So she left in’74, and in ‘74, by then I’d had a chance to come here. Two of my Yale students had come here, Marlan Scully and Murray Sargent, and the thing that made it attractive was that Scully was a sufficiently able operator that he went to the president of the university here, and showed him a book that Ursula had written, published by the Chicago University Press, on a certain gentleman called Pedro de Medina, a cosmographer, and it was a nicely printed book, beautiful Spanish manuscript, manuscript that would be hard to read except for somebody who had looked at paleographic materials, which Ursula can do. Well, on the basis of that, the president called the history department and said, “Look, there, you’re not going to get any…” (off tape)
…You know, everybody thinks that when one goes from one school to another, it’s for professional reasons, and it’s not uninteresting, I think, that it doesn’t have to be because you could do better physics at this college or that college or you like the dry weather of Arizona.
Let’s see — as far as — I didn’t really have any reason to leave Yale, except for this. But this was a very strong reason. And I lost something by coming. I had very good graduate students at Yale, and I think certainly I would have gone on having them. When I came here, I didn’t have any graduate students, and — I had a few post-doctoral people, and I’ve had very nice colleagues, not very many, because my interests are rather special. But —
But even with the Institute for Optics here, you didn’t?
Well, I have a joint appointment in that. The one thing that was much better here is, the computing facilities were enormously better, and, although I haven’t – I’ve worked very hard to make use of this, in some ways things didn’t work out as well as they might have, but I’m still hoping that it will work out. I’m working on it, as soon as I can. But the facilities here were very good, much better than Yale. Now, I had begun a lot about computers during the early Yale years when I got Murray Sargent as a student. He was first working with an analogue computer, which he learned about by working a summer at Perkin-Elmer, and then he began working on a problem I had, and he realized — his intention was to use the analogue computer to integrate the differential equations, but in the meantime he had learned about digital computers, and he never turned back.
Now, was he working at Perkin-Elmer before you got him?
That was just a summer job. It was the summer before he — he was an undergraduate, and I think maybe when he graduated he probably worked the summer at Perkin-Elmer, and came to know John Atwood, and some time about that time John Atwood came and spoke to me about laser problems, and arranged a consulting arrangement for me with Perkin-Elmer.
That was quite independent of the Sargent relation with Perkin-Elmer?
Yes, that had nothing to do with the Sargent connection. I suspect that Sargent’s connection was before my consulting, but I knew nothing about Sargent until he came into my office at Yale.
What kind of thing did Perkin-Elmer have you doing?
Well, it really didn’t amount to much. What it involved was going down and helping John Atwood and a fellow named Paul Lee. You know —
I know these names, I don’t —
He’s an interesting guy.
Lee. Paul Lee is living in Santa Barbara. He was, a certain year, he left Perkin-Elmer and went out to Santa Barbara, and in the early years, Perkin-Elmer set up a laboratory for him in the Santa Barbara area, and then at a certain point they decided not to do it anymore. He became an adjunct professor in physics. He’s now retired from that. I don’t think the adjunct professor was sufficiently enough to get him emeritus standing, but he is acting as some kind of a consultant to the Desert Research Institute that the University of Nevada has near Reno. He’s a very inventive guy. He developed the use of the tuning dip(?) to have stabilization. He was certainly one of the co-inventors of that.
Was that something you were talking to him about? I don’t know when that happened.
Well, at the time I began to go to Perkin-Elmer, I was interested in ring lasers. And I had a student named Gyorffy, a Hungarian refugee. He was very young, a more or less Olympic class swimmer who, to get out of Hungary and into Yale, was able to use his swimming ability, and he did a thesis on ring lasers. And they needed, in order to really exploit the theory, they needed computer calculations. Even though the Yale facilities were good, they were nothing like as good as they would have been here, or at least as they would be here now. So — but Perkin-Elmer had a computer. They had I think it was called Sigma 7. And the Sigma 7 could be used at night, so Gyorffy and I went down to Perkin-Elmer some nights after working hours and were let in by John Atwood or Paul Lee, and we put the equations on the Sigma 7. Well, that didn’t get too far because Perkin-Elmer began to feel that they had to charge for the use of the computer, it had to be apportioned to some budget, and that budget wasn’t available, and so that didn’t work out too well. Well, my consulting for Perkin-Elmer was successful as long as John Atwood wanted to talk with me, ask me question and have discussions and arguments, and at a certain point, he was moved to a different position, and the man who took over had a research section and didn’t really need me very much so the relation didn’t last much longer. It lasted about four years. I can supply the dates of that very accurately, because I for tax purposes I have records. My income tax records are in better shape. If you were auditing my income tax returns, it would be painful but not chaos.
You were in contact with Lee in the same way?
At a certain point, partly because Atwood went away, he’s still at Perkin-Elmer, but the research lab was not quite as much fun to be in. His wife had been a lecturer in biology at Yale, and she got to be a lecturer and she didn’t get to be anything more. At a certain point Santa Barbara wanted to make her an associate professor, so they did and Paul went with her. So there’s a slight similarity there. And then he was able to get Perkin-Elmer to set him up with some equipment. One reason why Lee is an interesting person is that he is highly original, exceedingly. I really haven’t known anybody who thinks at the wild and wonderful things that he does. He’s a pilot. He got a PhD in physics at Harvard. He, his first job was with Land, Polaroid. But he didn’t get along — this was at a time before Polaroid became a word on the tongue of everybody. He couldn’t get along with Land too well. He then worked for the CIA for a while, and he was considered to have just the kind of fiendish imagination that would be very useful for an organization like that. And at a certain point he didn’t want to do that anymore, and he got involved with some, I imagine electronics firm in the Norwalk area, Connecticut, and then for some reason or other, security and clearance came in, and Lee was supposed to tell everything he knew about certain people who were his friends, and he declined to do so, and so he lost his own security clearance. And then somehow he got taken in by Perkin-Elmer, and invented and exploiting the tuning dip(?) in a way that was rather important. Well, anyway, if you have occasion to go to Santa Barbara, look up Paul Lee.
I will. I’ll keep that in mind. I want to ask, in your bibliography, Gyorffy is listed as a co-author on articles on pressure broadening, and a man named Menegozzi is your co-author on the theory of the ring laser.
The ring laser, yes, the situation there is that Gyorffy escaped my clutches before — he wrote his thesis, a Yale thesis on the ring laser. But Gyorffy escaped my clutches before a proper PHYSICAL REVIEW paper was written, and Gyorffy went to England. His father was a professor of agriculture in Budapest, and at a certain point got to England, and Gyorffy went back to England to be near him, and Gyorffy is now I think a leader in physics, theoretical physics, at the University of Bristol, where he works on the theory of disordered salts (solids?). I haven’t seen him in a long time, but I hear from him. He’s doing well.
It makes me wonder how you work with your graduate students. When you were writing up the theory of the ring laser, you want a graduate student to be working with you on the write-up? You brought in Menegozzi because you —?
Oh, I don’t know whether it’s laziness or not, but I don’t mind having other people do the work. I like to be in a position to tell them what to do, because obviously I know it better than they do, but what the theory of the ring laser needed was some kind of calculations, and though Gyorffy did do some, he didn’t do as many as we needed to write up the paper. Menegozzi is an Argentinean of obviously some Italian background. His grandfather came from Italy, and went by the name Menegozzi, and he got a PhD in physics sometime in the early sixties, and he came to Yale as a, some kind of — No, it was a grant from the Argentinean National Research Council. And then he didn’t want to go back afterwards, because there were too many generals, and I was able to pay him an exceedingly nominal sum to support him, and he stayed in New Haven for a while, and when I came here, I could go on doing something like that but I couldn’t get him a proper job. Anyway, he worked on several very good ring laser paper was a good one, I don’t think it’s appreciated at all, but that’s a very natural conceit. And then he worked on a problem of the amplification of incoherent radiation in a laser type medium.
That was one that you co-authored?
Yes. And then he began working on another problem which in the end exhausted his already very large, very much worn out patience. He went away and got a job with a firm in New Jersey, where he — it’s research cartel.
No, just a final question on this Perkin-Elmer connection. Did you find this kind of discussion, with Atwood and Lee, would be carried back into your own work? What did this kind of consultantship mean in terms of your own research?
Well, what it meant was that one day a month, or maybe not quite so often, I went down, having phoned ahead of time to make sure that the date was a good one, and had what might be called a bull session.
There weren’t any noticeable ideas that you recall carrying back from there?
Well, I would learn of some problems that were of interest to them, and if I had any ideas, I would tell them, and I would even possibly think of doing something about the problem. They had a problem, for instance, in which an intense laser light was to be passed through a medium, which was capable of getting warmed and expanding, and they would have liked to have had the combination of electromagnetic theory and gas dynamics worked out for such a problem. I wasn’t very well qualified for it, but I thought about doing it, and in the end somebody on their staff already did something useful for them. I didn’t have much to do with it. It just wasn’t — I had a close relationship with Lee and Atwood but not with the other fellow.
You can see that the question of how industrial problems come to have an impact on academic scientists via consultantships might be an interesting historical one. That’s one of the reasons why I’m wondering, was any of the consultantship work important in some of your researches?
Well, getting to know Paul Lee was an important thing in my life. I don’t know that it affected — his bright ideas about the tuning dip came completely independent. He had been exposed to the theory, but he doesn’t, he thinks in non-analytic terms. To me, the tuning dip was something that came out of the algebra. Of course, I began to see what the physics it was. But Lee would think only about what the physics of it was. And he did that very well indeed.
Parallel to this question about consultantships, I have one in here about the military. Throughout the interviews, I’m finding a lot of interaction between military agencies and the various laser scientists, and I notice of course that you have some I guess Air Force funding for, cited in some of your articles. I just wondered whether you got very much involved with DOD, how you got those contracts, whether you were involved in government committees? This is mostly in terms of the Yale period.
OK, well, the first connection with government supported research was that $75 from the Manhattan Project, in ‘41 or so. Then the work at the Columbia Radiation Laboratory was all supported by the Signal Corps. Or some kind of joint services arrangement, I don’t know how much — there was lots of money for things that had to be bought. It had nothing to do — occasionally I had to write a progress report.
I sometimes met the contracting officers when they visited the place. I did come into contact with one or two of those, who turned out to be quite important in getting funding in the future. When I went to Stanford, I was able — so at Columbia, I really just had the best of all possible worlds, as far as funding was concerned. It was funding, it was a going organization, it was easy to get continuation. Of course, through the years, that support for Columbia has dried up somewhat. Not because I left but just because the times changed, and the people got older. The people who were friendly in the services no longer were in the service, and the people who came in didn’t appreciate the wonderful things of the past. When I went to Stanford, Felix Bloch had an ONR contract. He was able to get them to increase it a little bit because I was coming. And I suspect that I had something like $25,000 a year for research in the early fifties. One very important person in that contract was a local ONR representative whose name was Urner Liddel…and I know the gentleman that I met in some connection or other, but I can’t remember what right now. I think it was at Columbia, was a Paul Johnson. Paul Johnson was a captain in the Navy, but he was really a patent attorney. He didn’t have much of a role to play at Stanford. Now, when I went to Oxford, I had a certain small contact with the European office of the Air Force, research under the Air Force, and I suppose that came from Leonard Schiff, who was a kind of senior scientist, advisor, for the Air Force. But I believe it was at that time that I came across Captain Johnson. Well, I didn’t have any contract support in Oxford, but I was given clear messages from the Air Peace that if I were to apply, I would probably get something. The Air Force did support some research in Europe. But I didn’t really know how to write a proposal, and it didn’t seem worth the trouble to learn. When I went to Yale, Vernon Hughes had perhaps one to two hundred thousand dollars a year of government support for research, and was able to get that approximately doubled because I was coming, so that the research at Yale was very well funded, and the, Johnson was definitely involved in that, in the earliest stages of it.
Were you starting out to write proposals, or you still didn’t have to write them?
At that point I had, not to write the proposal, but I had to write the papers that dealt with the projects that I was involved with. Hughes was very good and willing to take care of the real nitty gritty of the proposal writing.
You were also supporting your graduate students on these.
Yes. Most of this money went for graduate student support. If you had a typical budget of $100,000, the amount that you could spend on equipment might be 10 or 15 thousand. The rest would go to overhead and salaries and increasingly the concept of summer compensation, when the principal investigators came in.
How many graduate students typically would we be talking about? How many did come to work with you here?
Well, both at Columbia — I think at one time I counted that I had about ten, and at Yale, it might have — I mean at one time — at Yale, it was getting pretty close to that.
That’s a lot.
Was this a matter of, you would be working out your own general research ideas, and then —
Well, there’s a long list of laser papers in the Yale years, where there was Scully and Sargent and —
— the man whose name I can’t pronounce —
— Gyorffy. Spencer. A Chinese, what was his name, Yang or Wu?
Yes, Wang. I can’t remember more. Oh, there were people who were doing experimental work, on atomic physics. The bulk, I think at Yale there were the two groups of students, people doing atomic and molecular physics and people doing laser physics, and they didn’t overlap too mach. Paul Berman was one of those students.
So then it was a matter of going through Hughes all the time.
Yes. I really had it very nicely arranged. Somebody was always there. There were friendly contract managers, people who had been very impressed with how nice science was, and how useful it had been, with whatever agency it was. Johnson, who was a captain in the Navy, was in a bad position when he worked for the Air Force because a captain doesn’t amount to very much in the Air Force, especially a captain in the Navy, and — who was in fact a patent author — anyway, he was very friendly and helpful. He also — it was kind of an interesting hobby, he made and repaired old violins. Well, in due course he was retired and he moved out of the Air Force and he went into NASA, and so throughout almost all of the Yale years, I had in the laser physics support from NASA.
Yes, I noticed that. That was Paul Johnson?
That was due to Johnson, entirely due to Johnson, and when he left, I think he went through the normal retirement procedures, — in the meantime, Urner Liddel had stopped being an ONR employee. He had moved into NASA, and he was some kind of a, he was never anything like the director…(off tape)…and this NASA physics committee met several times a year, in nice places like Pasadena or, we had two meetings in Puerto Rico near the (radio) telescope facility at Arecibo. We had to be inside the United States. We couldn’t meet away from the United States. Anyway, the connection there greatly supported the NASA contract, not directly but indirectly. That NASA support continued until after I got here, and it tapered off. And each time I was moved from one agency to another, they were getting increasingly applied, in what they wanted to do.
Oh, were they? I just assumed that you could choose whatever you wanted to do.
Well, that’s what I did do, as long as I was allowed to do it, and at a certain point they began to want specific things, and when they wanted something that was too specific, I couldn’t give it to them.
Was there some of the work which you did publish that came out of their wanting one thing or another?
Oh no, I think I just — I wanted to work on certain problems in laser physics, and so I did.
I see, so it was just a matter of their giving support, it wasn’t a matter of their commissioning any work.
Yes. Well, what appeared in the proposals and what was accomplished were different, somewhat. But that’s — I’ll tell you who, if you want this material, Vernon Hughes has this and ten times more.
OK. Where’s he?
He’s at Yale. He’ll be retired from Yale quite soon, but — so he might be at one of the high energy laboratories like CERN or SLAK or — Anyway, by and large the funding was here and was greatly facilitated by the cooperation and initiative of Vernon Hughes, so — Now, when I came here, things changed, because before I came here the Air Force was timing the Mansfield Amendment, OK, and that meant that the Yale support was practically going to dry up. Not must mine but for Hughes. We were both going to get chopped off completely. But there was an Air Force contracting officer named Winnersten, I believe, Colonel Dwight Winnersten, and he was very supportive, and he was on the verge of retiring about the time I left Yale. He was very helpful in making it possible to go on getting some Air Force support here. So when I came here, I managed to bring something on the order of $70,000 of Air Force support here, and from reasons that were appropriate at Yale, that was dedicated to experimental work. The Air Force support has gone on every year until a year ago and then it disappeared. But it did keep going on ten years. And the amount got cost of living increases, so it didn’t quite double but it was very nice. The experimental work, I see in retrospect that I should have managed things differently. I should have converted some of that support to the theory that I wanted to do. The experimental work was some work that I wanted to have continued, and so I — I’m now at the point where I have no contract support, and there are plenty of reasons for it which I don’t think would be a — I have tried to get a few contracts to do what I want to do, and in recent years it’s been very hard. See, I make what I think are very good proposals, and sometimes I come close, but —
I find that amazing, I must say.
Well, I’m sure if you talked to Bloembergen, you’d find that he’s got complaints about the funding support. That shocks me more than my own sad story.
Both I find pretty shocking. Whom might they support, one wonders? But let’s see, but your theoretical papers at Yale, they say Air Force OSR.
Yes. You see, at Yale, the NASA support didn’t amount to very much. For a while it was 30 thousand, then it became 20, and they were offering to cut it down to 15 and 10 and then it disappeared entirely, but it wasn’t enough to support the number of people I had, so some of the laser work was moved into the Air Force. It was sufficiently large and broad a mandate to cover that. But the Air Force money that I brought here would have required a little initiative on my part to get moved, to cover theoretical work, so that I did have some support coming out of optical sciences, which supported (?) when he was here. And so — but (?) wasn’t supported by the Air Force money here. It would have been better if I had somehow managed to rearrange things.
Were you ever tempted to some laser experiments, in addition to the laser theory?
No, I think the experimental work I was doing did not involve lasers. It involved microwaves, and to get into such a different frequency range wouldn’t seem to … I’d rather not. Now, there is one exception to that. The support at Yale came from several agencies. First of all I told you about the NASA, I mean, not first of all, but I told you about the NASA support. The Air Force support. Before the Air Force began supporting, they were supporting some, but ARPA came in at a certain point, and ARPA was at a point where they were willing to consider genuine physics experiments. That wasn’t always the case, but at one time, they were. And I put in a proposal for what I thought would be a way to measure the spectrum, the vibrational and rotational spectrum of the hydrogen molecular ion. This was about ‘67, and I was going through ordeals(?) with that proposal. Well, the thing that was wanted to do there was to make some kind of a discharge involving molecular hydrogen and get it ionized, make some HB plus, and then shine laser light into the material, and somehow detect whatever transition had taken place.
Well, I got an ARPA grant for three years for that work. And I had an idea about how to do the experiment, and — but for two of the three years, nothing happened, because I didn’t identify a student or couldn’t find a student who would work on it. I myself am not an experimental physicist. I only — well, a comparison that I don’t mean to involve bragging but it might seem that way, J.J. Thompson was working in that way. He did not do any experiments himself, he just told other people what experiments to do. That’s my mode of operation. That doesn’t mean I’ve never had a screwdriver in my hand or anything like that, but it means that generally I can find somebody who’s much better at experimental work than I am, so — Well, then I heard about a possible post-doc who was getting his Ph D at Michigan, and he had done very nice work there, and it seemed that he wanted to be a post-doc at Yale and I was able to get him to come. His name was Wing, William Wing. And Wing came and in due course heard about the problem I thought he might like to do, and he listened. He was a very argumentative type. He could hardly agree with anything I said. But nevertheless, he was obviously a bring fellow. Well, he said he would like to take a day or so to think it over.
So he came back after a couple of days and said, “Yes, I rather think I would rather like to work on that experiment, measure the spectrum of the hydrogen molecular ion, except that I’ve thought of a better way of doing it.” Well, of course I liked that very much, you can imagine. But I had him explain to me what the method was, and after he’d explained it I said, “Yes, you’re right, it’s much better. Let’s do it.” So he set about doing it, and he put an apparatus together, and began putting it together around ‘71, I think. It’s a long complicated thing to put together, and he had to get a lot of things. That involved a laser. This is the one instance where a laser was closely involved. Well, that apparatus was put together, and it turned out that when I came to Arizona, Wing also came to Arizona. He had been an assistant professor at Yale, but the department had missed the chance to make a good appointment and decided not to give him tenure. So he was willing to come to Arizona where he would get tenure. And he had a chance to try the experiment once at Yale. And it didn’t work. Then it was moved here. In order to be moved here it had to be cut into pieces, and, I’ll show it to you, and first, there wasn’t — this space here had been the former quarters of the mathematics department, and this was the department office, and then it became the headquarters of the Oriental languages department. This was the department office. When we came, this whole floor was to be available, at least this part of the floor, but there was no plumbing, no wiring, no water, no lab facilities of any kind. So there was a considerable rebuilding going on, which took the first few months that I came here. Anyway, before six months had passed of arriving, the experiment — so the apparatus had to be put up in Optical Sciences, and sat in the hall waiting to go into a small room, which would require further cutting up. Well, in the end it turns out that space became available here. The apparatus was moved down here. Before six months had passed from the day of arrival, in Tucson, the experiment was working!
That’s very good.
Yes. Let’s go look at the apparatus, I’ll show you… any financial support that involved what one would call peer review, and I tend to think that, admirable as peer review might seem, I’m very glad to have escaped it.
What are your particular quarrels with it? Do you think it only supports sort of normal work, not —
— yes, something like that, yes.
It’s an interesting question, because your work has been very much followed up, as far as I can see. For example, your semi-classical paper in 1964, well, of course, you had put out a lot of that in lectures and so on, but there was a lot of interest in that and follow-up work on that. So that it’s not as if you were just sitting there doing work all by yourself and nobody was paying attention. People were very much paying attention.
Yes, I think you’re right. But they — it really wasn’t needed. You could build a laser whether you understood a particular formal theory of it or not. You could build a laser whether you had the most outlandish ideas about radiation was like. So it—
Well, but there were many — now, you were very interested in what physics was. You were interested in lasers for a number of reasons, as far as I can make out, like what are irreversible processes, and how do they come to equilibrium and things like that. Weren’t the physicists who were interested in that kind of thing following what you were doing from that point of view?
Well, I’m sure they were, to some extent. The people from whom I learned to like such things were people like George Uhlenbeck and like — I don’t think he ever really had occasion to pay much attention to the laser theory. I think he would have enjoyed it. But probably if he had heard about it earlier than he did, because he was getting older
I don’t actually know —
— it led me to the possibility of understanding some things about the approach to equilibrium that I wouldn’t have had otherwise. And I talked about that work at Trieste at that conference that was dedicated to the Dirac on the occasion of Dirac’s 70th birthday, and Uhlenbeck was in the audience, and I don’t think he really appreciated it very much. Maybe it was a bad lecture.
I guess I don’t know which of the papers that is. Here, I don’t even know if I’ve got the right page there.
Well, let’s see — yes, “Approach to Thermal Equilibrium,” and a sort of thing that followed that was called “Irreversibility.”
I’ve read the second one but couldn’t get hold of the first one.
Which one, this one?
Yes. It was just not in the library when I went.
Maybe I even have a reprint, although I’m not sure.
Maybe we’ll begin with your interaction with Scully and his initial approach and how you —
You could of course be getting that from Scully too. Maybe better.
But I’d like to focus on your own feeling about how the thing should be done and that kind of thing.
Well, in the — for a long time, I didn’t have any idea that the electromagnetic field had to be treated quantum mechanically, because it would seem rather silly to speak of light quanta when you’re dealing with the electrical current that you get out of a wall plug. You don’t buy electrical energy from Consolidated Edison or Tucson Electric Power at so much a photon! You buy it by the kilowatt hour. If you did talk about photons of 60 cycles power you would be talking about a very large number of photons, and it wouldn’t really be a very good concept to bring in to the discussion unless the conditions were exceedingly well controlled, so that it made sense to say that you had a certain number of photons. There would be a similar — in a mechanical problem, the similar problem would be to consider a simple harmonic oscillator of some kind, say consisting of a child on a garden swing, and deciding whether you would treat that by an equation of motion, like force equals mass times acceleration is equal to a constant K times the displacement of the swing, and use Newton’s law of motion, plus laws of inertia, or whether you would begin to quantize the problem and talk about the stationary states.
Well, the stationary states were there, at least in an ideal situation, but it would be unrealistic to consider in the case of a playground with a number of other people around perturbing the system by just being there. So have a laser produces enough light to see, it’s producing radiation that can be described in classical terms. And only in very special limiting cases, indeed hardly ever, is it important to consider the quantum nature of the radiation. So in the work at Stanford on molecular beam, ammonia beam lasers, and the work that got finished at Yale, started at Oxford, finished at Yale, on optical masers, the radiation field was treated without reference to the quantization of the radiation field. The matter, the atoms within the things that constituted the medium were treated quantum mechanically, but under the action of a known or knowable electromagnetic field treated classically. But all the time that that work was going on, I continued to hear discussions about what the theory would consist of, and it seemed to me that though a lot of people expected the quantum theory to be brought into it, quantum theory of radiation, I knew something about that subject, not a great deal but some —
— these discussions, were these sort of the (Roy) Glauber, (Leonard) Mandel, (Emil) Wolf kind of things? Or something quite different?
Well, Wolf is, let’s say, not really doing quantum theory of radiation. Glauber is, whenever he wants to, is. And Mandel, to some degree too.
I just meant, was this for example the controversy at Paris that, when you say you were hearing things about this —
Oh, I don’t really remember a controversy at Paris. There’s just a little history there. I was invited to give the first paper on the program. There was a kind of an opening session at which P(?) Grivet was there at the age of 90, and was able to walk across the stage but not very much more than that, and after the conference got opened, I gave a talk. And I was supposed to submit the manuscript for the talk. The manuscript was pretty far along, it was more or less written exclusively, though I did publish in ‘74 — the Paris Conference was in February of ‘63. And so I didn’t submit the manuscript. I think I did submit an abstract of it, a very brief one. Anyway, the editors of the book, of the two volume book that described the conference, Bloembergen and Grivet, did not have any indication of what the program had been. They simply published the papers that, for which they had manuscripts. There was no indication in the book that I appeared at the conference.
I know, I looked for you in the book.
I do have a book that was printed before the conference that indicates that I was on the program and that I had a certain talk and so on, but I think I was being punished for not having sent in a manuscript. The reason that I didn’t send it in is that I was still trying to figure out what the physical explanation of the tuning dip was, which of course involved burning(?). But I think it wasn’t clear to me at the time.
Well, I distracted you in the middle of a story because you were saying that you were not seeing any reason to use the quantum theory but you were hearing about it, and I was wondering whether the Paris meeting was at Les Houches where Glauber and (Norman) Kroll were among other people and whether these were the places you were hearing about it.
Oh, let’s see, Kroll was a great force for physics, wherever he is, but he wasn’t really concerned with laser problems. Roy (Glauber) was working on his theory of the coherent state of a simple harmonic oscillator or more generally the electromagnetic field, and he thought at the time at least that by having that theory set up, a fairly general and formal thing, but very pretty, that it would surely help attain, help in the attainment of a quantum theory of the laser. Well, at the time of that conference, I didn’t yet know how to formulate the quantum theory that (Marlan) Scully and I gave but it was beginning to grow on me, how to do it. And near the end of things, I had a pretty good idea of how to do it. Then when I came back to Yale, after the summer, Scully came in order to work with me. He could probably tell you stories and he’ll not only tell them in a better way than I can, but in case you want it, you’ll know it’s there. He came in to me and said he wanted to work with me, and I found out he was a first year graduate student and I told him that I didn’t take first year graduate students, the reason being that typically you would have to pay them something while they were studying and taking the courses, and my contract money wasn’t all that much that I wanted to waste money that way. I wanted somebody else to support them when they were learning. And so, well, he then proceeded to argue me out of it. He pointed out that he had great qualifications and that he was a very unusual person. So at a certain point I realized that I was being rather arbitrary, and …(off tape) OK, so I told you how Scully became my graduate student. He happened to say the right words at the right time. But Scully is very good at that. He can very quickly sense what the right words are. He’s very good. If you turn off the tape a minute… Now, —
So he came, but you said he already came with ideas?
He already had been reading on his own the rather intricate papers that were published by a number of people, particularly a paper by (Ilya) Prigogine and (?) Rosenboiss. And in general, they were working a theory in which you would write down some kind of an equation of time evolution of a system, without really specifying what the system was, and then go on as far as they could and perhaps beyond where they could go, without ever coming to decide to solve a certain particular problem. Well, at a certain point I managed to persuade Scully to begin to look at the problem in the way that I felt it had to be figured.
And that was this way that you said you’d been thinking about since —
I began to think about how to do it in lasers, but without getting it written down. Scully was enormously good at telling at the blackboard what he had been doing or what he had been thinking about or what he had been reading, and so it was a sheer pleasure to work with him, in that he would give me a lecture and I would tell him what was wrong and he would perhaps tell me where I was wrong, but we would learn something, both of us, in the process. So anyway, the technique that evolved was to consider a rather simple system consisting of the cavity, the typical cavity of the laser, whatever it was, into which one atom in an excited state was injected, and at a time when there were, let us say, N photons in one mode of the radiation field. Then in the course of time the atom would make transition from its upper state to its lower state, simultaneously with the increase in the number of photons in the cavity mode. And a little later transitions would be made the other way. The atom would go from its lower state to its upper states and there would be one fewer photon in the cavity.
The theory consisted of the bookkeeping of the (?), essentially the wave functions that would describe these various possible states. It was really very similar to what had gone on in the semi-classical theory. In that case, the electromagnetic field that was acting on the atom was one that you assumed could be treated classically, and you let then that field do what it wanted to, to the atom. The atom acquired a dipole moment. The dipole moment generated some radiation, all as a consequence of Maxwell’s equations. In the quantum theory, as Scully and I worked it out, the electromagnetic field was generated in the act of emission or of absorption of the atom caused by the mode of the radiation field that had a specific number of photons initially. And it was a fairly obvious generalization of what had been done on the semi-classical theory, but it had the advantage that the equations at all times had at least some recognizable relationship to the equations in the classical theory.
I do want to ask you, at lunch time you said that you tried to seek a model that is not so realistic that you can’t analyze it but is sufficiently realistic so that it has something to do with the world. I don’t know, I may have distorted what you said, but I’d like you to, I’d like to get a more precise formulation of that from you, how this particular model, was this already at the stage where you thought it was sufficiently precise, or what stage was the model at?
Well, a gas laser is something that probably has billions and billions of atoms, and if you treated the problem well enough, you would consider all the atoms, all interacting in whatever way they were interacting. The way of making a model in which you deal with one atom at a time makes an enormous simplification. It also represents a bit of an idealization, because it neglects the fact that one atom disturbs another atom, and in some situations, the disturbance of the atoms play a very important role. In other situations it would play a very minor role. But by downplaying the interactions of the atom, they all interact with each other through the common medium or the electromagnetic field, but they don’t interact with each other on an atom to atom basis.” At a later stage, the theory can evolve so that you do take the collisions of atoms into account, and Paul worked on theories of that kind, and in fact he made that his career. He hardly works on anything else but that problem. He’s gone much further with it than I would have known how to do.
So this was then, we’re in fall of 1964 at this point.
It sounds very likely. I think the first Scully publications were ‘66.
But the first thing I’ve seen was the Puerto Rico.
The Puerto Rico, when was that?
That was in the summer of ‘65. How did you come to give that talk?
Oh, was that one of the quantum electronics conferences, or was it a similar conference?
I think it was a special similar conference.
It was a special similar conference, yes, and I don’t know who sponsored it or anything like that. Obviously somebody did, because I wouldn’t have gone to Puerto Rico — well, I don’t know, I could easily have used the Yale grants. But I don’t think I had to.
I’m curious how the talk was received there, if you have any memory of that. What you might have —
— oh, I think that if there was applause, it was polite. It was, I would say, I don’t think it created a great sensation.
Of course, Bloembergen, Townes, I don’t know if they would have been working directly —
Well, as I’ve indicated, I didn’t really think one needed a quantum theory, for laser. I was making it because it was there. You know, like Mt. Everest. And —
I see. I don’t remember if Glauber was at that meeting or —
I sort of think he was. Let’s see, there is a book of that conference. At a certain point, we can move from here up to my other — yes, I have the Grivet-Bloembergen volume here… This is Paris. The Optical Science Paris(?) books and I’m pretty sure I have the Puerto Rico books.
Well, OK, if you remember anything of your own, of that paper, or anything at the conference that interested you, or anything that people said to you about it — I guess people like Haken were just not there. I don’t remember.
I’ll tell you about Haken (…) I ran into Haken for the first time at Heidelberg, and I would think it was, it’s possible to find out, because it was a conference in which Kopferman was the organizer, and he was still alive. He didn’t live much longer. And I was pretty far along on the laser theory at that time, but I didn’t talk about it at the conference. I talked on something else. But there was a talk by Haken about laser theory, and it seemed to me that he had some very good ideas, and I was a little upset, and not quite in the way that Watson was disturbed by his fears of what Pauling might do, but nevertheless, somewhat disturbed, because it seemed to me that Haken might very well be a serious competitor, which in fact he certainly has been. But he was talking about a program, in which there were lots of things to be done, and I guess I felt that if I had talked on that subject, I would have had something a little more specific to say than he said, but nevertheless, it was clear that he was very close to getting the same thing. So the next I found out was at the Les Houches. Which year was the Les Houches, ‘64?
‘64, OK. Haken didn’t come to that summer school, but he had a student of his, his name was Sauermann. Sauermann gave a talk on the Waken theory as it seemed to be at the time, and it seemed to me to be a dreadful mishmash of classical and quantum descriptions — he would write down a symbol like E, which was intended to be a creatio or annihilation operator or a field amplitude — it didn’t didn’t seem to be specified too clearly whether he was talking classically, semi-classically or what, and in the end he didn’t seem to be coming up with a result. This laser that’s being described by the model we’re considering will read such and such a steady state with a certain intensity of output and a certain frequency of output. He didn’t seem to be getting to such kind of information. It was hard to tell whether it was the quantum theory or classical theory. The interpretation I have is that Waken was a victim of a bad education brought about by the Second World War. That is, he was self-taught, or he was taught by people who perhaps were self-taught, I don’t know, but he had missed the great traditions of German theoretical physics. So now, I’ve met Haken a few times later, and he’s been much more energetic than I have. He’s written books. He’s invented or exploited a word, synergetics.
Oh, that’s right, that’s what he’s been doing.
That’s one of the reasons, he’s a poet.
I see. He fits in with Prigogine as a poet.
In the zoology of my companions. I wouldn’t myself have called these gentlemen poets. They’re delightful human beings. But Haken is a lovely person, and when I’ve heard him talk, he sounds better than I find it to be when the details come out. I think his book on laser physics is a mess. But of course it’s in competition with the one that Scully, Sargent and I once wrote. By the way, one of the things that I found in the mail is a royalty check.
But I think it’s going to be for a very small sum. The book is still selling, but it’s not selling — oh, my goodness! I agree this looks — would you believe? I’m getting one-third of the royalties. The way we, I lent my name to the project, Sargent wrote the book, and Scully, I’m afraid, wrote an appendix which would have been better left out.
Is that the one on the relation between — who wrote the chapter on the relation between laser physics and other very interesting topics in physics like Bose(?) condensations and so on?
That probably was Scully. Well, anyway, the royalties were divided. I got, I’m sorry, I got one-quarter, Scully got one-quarter, and Sargent got one-half. So my one quarter is $199 for this half year.
I see, so that’s not a big sale.
No, but it’s better than the $75 I got for starting the atomic age! Well, —
That’s the ‘74 edition? It’s had three printings.
Oh, it’s never been brought up to date. It’s had three printings. I think that Murray is now involved in writing a laser treaties with other colleagues. Some of the people he knows in Germany. Well, at one point, I did subsequently meet Haken, and again, was charmed by his being there, and he tried to explain to me what the differences were between what we had done — what he perceived to be a difference was that I had chosen a good notation. He didn’t. I didn’t return the compliment by saying that he had chosen a good notation. I think he knew better. His notation was abysmal.
But that wasn’t your chief quarrel with him, was it? What was your chief quarrel with his, a kind of messiness?
Oh, I would say that he didn’t manage to define the problem before he started talking about it. No, I didn’t tell him that. I like him too much to — I don’t know that it would hurt him if I told him, but I decided not to tell him. I think there was a quotation from Richard Feynmann about notation. Scully used to have it pasted to his filing cabinet. I can’t quote it exactly, but it was something about, getting a good notation is half the battle, or something like that.
I see. Well, we were up to Puerto Rico and I guess I asked you about Haken. He wasn’t there.
He wasn’t there. Mel Lax was there.
What was he doing at the time?
There were other people I can remember who were there, but I don’t think they would be particularly known in laser physics. Peter Hammerlingh was there and some of the MIT, Bonn was probably there. So I really — at one point, Roy (Glauber), he heard me give a talk and he came up afterwards and said, “My God, Willis, you’re mixing all these different fields, quantum mechanics, electromagnetic theory, this, that and the other thing,” I don’t know what they all were any more, and I was rather pleased by his perception and kindness to say such a thing.
Then after Puerto Rico, you and Scully published this little PHYSICS REVIEW Letter in ‘66.
There was a Letter. Then there was a paper.
Then there was the long paper of ‘67.
Yes, which was unfortunately the first part of six papers which rapidly tailed off into nothing very much.
Were you planning all those papers at the time you wrote the general theory paper?
Oh, I think at the time we wrote the first paper, we probably could see that there would be a second paper, and then, we were of course in some kind of competition with Mel Lax, who had a very different way of looking at the problem, also a much more general way. But the difference there was, we were starting with a specific model, and pretty well sticking to the model. Mel had a very much more general point of view, which would allow him to apply the theory, give enough time, to a much wider class of problems. He didn’t begin by wanting to discuss laser theory. He began by wanting to discuss something that would probably be in competition with Prigogine and Rosenboiss, only I don’t think Mel thought of it that way. I’m sure he just thought of it as the right way to do the problem and a wrong way.
I guess I don’t completely understand that, because when I look through your papers I have the feeling that you’re always very interested in the general application to pushing back the formalism of quantum mechanics, that the laser enables you to carry through, so that I always have the feeling, maybe this is quite wrong and I’d be very glad to have you tell me, that you really have some very general things in mind, that you would like to extent the methods of quantum physics and be able to apply them to biophysics or what have you by doing a good job on the laser. Is that just a false impression? That seems like a very general goal.
In the big paper, No. 1 of the quantum theory, of the laser, there is a paragraph in which there’s some mention of whether this theory could be regarded as an exercise in the direction of making a theory that would even allow for a description of living things. But one is so far away from having a good model for that, that it was rather cheap talk, I would say.
I guess I wondered —
If you want to have a description of life, you have to have a theory that will handle any rather large molecule or aggregate of molecules, and you have to be able to describe the fact that this animal is breathing and eliminating waste products, and even some kind of interaction with the environment, like sunlight, and that’s a lot more complicated than having a single two level atom interacting with something that are acting like simple harmonic oscillators.
Would a little paragraph like that be you or Scully or both?
I think I wrote that paragraph.
And how —
I don’t think this has caused much of a stir. You might even be the only person who ever read it.
I thought it was wonderfully profound, but useless.
Well, I read it and my curiosity was aroused, as to how that idea stood in your whole scheme of thinking, whether you really had any far-reaching plans to pursue physics that far.
Well, obviously just knowing that you have to take a big molecule to pursue this program wouldn’t be enough. You would also have to take a molecule that is a good candidate, deserving of such consideration, so I would have to learn some biology. And that gets you into borderline about what’s quantum mechanics all about anyway? What’s the meaning of quantum mechanics? What’s measurement? Things of that kind. Well, I work on such problems and I even think I make progress, but I find it hard to make enough progress, and practically anybody who thinks about such problems has a lot different from anybody else who thinks about such problems. It’s very hard to get into a meaningful discussion.
Is there a way in which you combine thinking on such general problems and thinking of the more specific problems? Is there any kind of (?) or trade-off between the two? I just wonder how it — or do you do one for relaxation from another?
Well… I’m afraid, I’m looking for the Dirac lectures — let’s see, taking things that I — is this something you know about?
OK, you’re welcome to it if you want it. I’ve got more than enough.
Sam gave me a copy.
OK, what I want is — here’s the Dirac lecture. Yes, one for your very self.
Now, this simply took the stuff that was in the quantum theory of the laser, which of course was supposed to be dealing with the quantum theory of the laser, and turned it around so that I could call it an article on the approach to thermodynamic equilibrium and other stationery states. That took care of the lasers. See. And so, all of these pictures are not literally but potentially results of solving a certain differential equation that some people call the Scully-Lamb equations. I think Mel Lax used that phrase before we did, but anyway —
— deep density matrix —
Yes, what’s considered is a stream of two level atoms that’s supplied by a harmonic oscillator, and it’s if the two level atoms have a temperature in some sense, then pretty soon the oscillator has that temperature. That’s the approach to thermo-equilibrium. Now, I’ve been spending more time recently thinking about the problem of the quantum theory of measurement, and there are several things about that too elaborate to mess with now, but one of the models for dealing with the quantum theory of measurement is the following: let’s consider a harmonic oscillator. Now, this might be a vibrating mass in a gravity wave detector. I’m not sure whether it might be a simple atomic or molecular system. So it could either be a microscopic oscillator or not. Then you send by a two level atom, and I had them coming by with let’s say they were 40 percent in the upper state and 60 in the lower state, and then I would assign a temperature to these atoms by…(off tape) Well, what happens is, now, the atom in the upper state is supposed to only be able to go to the lower state by raising the oscillator or vice versa. The atoms in the upper state may make a transition to the lower state. I’m sure I’ve got it turned around. And raise the oscillator and vice versa. Turned around. And one can work out in detail how the distribution for the oscillator is changing with time. And it’s really just a problem of the quantum serial of the laser-cast. Well, in doing this, you pay no attention whatsoever to whether the atoms that fly by are in fact in the upper or lower state. You say, whatever it is they do, they’ll do, and you figure out how the density matrix changes for the oscillator.
Well, if you wanted to make a model for the measurement, you might proceed in a slightly different way. You would say, here is a mechanical oscillator, it’s got some wave function. I would like to make some measurement on it. One way to make a measurement on it is to let one of these atoms fly by, let us say in the upper state or in the lower state, say in the lower state, and then depending on the state of the oscillator, there would be a somewhat different probability for having this atom go to the upper state. So if you were to make a series of measurements, on the oscillator, by looking at what came through, and found out whether you had the upper or lower state, you would be able to learn something about what the state of the oscillator was like. And if the state of the oscillator was changing with time for some reason — for instance, there might have been a passing gravity wave — then you could investigate the degree to which you could hope to learn something about what gravity wave disturbance was like by studying the effect on the atoms that had passed by, and so to say had a look. They would go by and look and then tell you what they found. Well, that’s a specific model for a quantum mechanical measurement, and not a very good one, I might say, but at least it’s a model. And so I’ve been able to turn this paper around to apply to a problem of that kind, too. It’s still in the process of being worked out. And so —
Before we go any further on, I’d like to ask you —
— but the conclusion I have is that one can’t begin to understand what quantum mechanics has to do with physics of living things until some preliminary understanding is had such as what quantum mechanics really means, and how do you find a good model for a candidate for a living system. And it’s got to be a very, it’s got to be a simple model but it can’t be simple because it wouldn’t be living if it were simple.
Is this a conclusion that you came to after you wrote that paragraph in the ‘67 paper?
Oh, before and after. This particular model that I told you about based on this stuff is relatively recent, but — well, another treatment of life and physics is in a book by Schroedinger — what is it called, WHAT IS LIFE?
I think so.
Or something like that. Reading that is a very disappointing experience for me. I don’t find out what life is. But I just get the impression Schroedinger didn’t understand quantum mechanics. But I think it’s a greatly admired book. It’s beautifully written.
I don’t remember when it was written, so I don’t know —
— a long time ago —
— whether he was in a position to understand quantum mechanics that early.
No, or that late. You lose a few…
I did want to ask you, between the Puerto Rico talk and the general theory of, that was published in ‘67, the general theory article, whether there were any specific breakthroughs or insights that we ought to record here as part of the historical story?
Well, no, I don’t think so. Let’s see, the first two of those papers on the quantum theory of the laser were I think — the third paper dealt with the photoelectric counting statistics.
Yes, that was interesting.
That was interesting but it was a very messy paper, and we did not really do very well in explaining anybody’s observations an photoelectric counting statistics. Whereas almost anybody who did such work was comparing his observations with the Lax theory.
Oh, I didn’t know.
Yes, I think — and to some extent, that probably would be attributed to the fact that we didn’t understand things well enough to make the paper good enough. Partly that, although it would have been better if the Lax theory could have been more specific, it got along amazingly well without the need to be.
Were you in touch with people like Armstrong and Ellis and all these people who were doing these photoelectric measurements?
Oh, we really didn’t have much to offer them. The third paper just really, we hadn’t worked up the level of complexity that the thing needed to have considered. Now, there was a kind of an offshoot of this sort of theory, of — I had occasion to have to write an article in a Festschrifft, that isn’t the French word for it, for (Alfred) Kastler, and I hate to write Festschrifften but somehow decided to do it, and here’s something called “The Photoelectric Effect Without Photons” and that’s on page 363. And that paper has a certain amount of mathematical analysis about what the photoelectric effect would be like if there were no photons. And it’s a short article, and it says, “In fact we shall see that the photoelectric effect may be completely explained without invoking the concept of light quanta. To be sure, certain aspects of nature require a quantization of the electromagnetic field for their explanation. For example. For example, one, Planck distribution law for black body radiation, 1900. Two, Compton effect, 1926. Three, spontaneous emission, Dirac, 1927. Four, electrodynamic level shifts, 1947. The photoelectric effect is definitely not included in the foregoing list. It is an historical accident. The photon concept should have acquired its strongest early support from Einstein’s consideration of the photoelectric effect.” This rewriting of history is, shall we say, not catching much acclaim. But —
Of course Einstein doesn’t, he just uses the photoelectric effect at the end of that paper as an example, but the initial considerations as I remember are quite different in that paper. So in a way you were right, it was a kind of accident.
Well, I think the, at that time there was a possible theory around, the Thompson model, a sphere of uniform density of positive charge with an electron of negative charge or electrons bouncing around inside, and if you turn down a classical electromagnetic wave as if, for instance, from a Herz oscillator, then you could work out the equations of motion of the electrons in the presence of that electromagnetic field. You couldn’t solve them without a computer, however. So the physicists of that day weren’t able to follow out the consequences of the theory that they had. If they had followed out the consequences, they would have found that the results didn’t match the experiments. But they didn’t in fact follow out the consequences. They didn’t work out the consequences of the theory. Well, this particular article is simply working out a little more in detail what was known quite early. There were two papers in 1926 that in effect pointed out that you do get the photo effect, just like you would like to be without any quantization of the electromagnetic field. One was Wentzel and one was by Guido Beck.
You introduced this by saying this was related somehow to the theory of photoelectric —
— well, yes, because there was some mathematics going on there which is Scully’s simply transcription of the mathematics that went on in the second and third parts of the quantum theory of the laser, for this problem — that is, what he’s concerned with is showing that if you shine light on an atom that can undergo photo emission, with the probability of having the atom remain falls off exponentially with time. And that takes a little as you can clearly see it’s got to be that way, but to prove that it’s going to be takes a little bit of machinery which Scully had available.
Now, another thing I wanted to ask you, is E.T. Jaynes work at all connected with the kind of thing you were thinking about?
No, not really. It’s not unrelated, but —
I mean, you were very much interested in the connection between semi-classical and quantum theory, and I just wondered if as where you fit in that whole picture.
Well, Jaynes is a very very likable fellow. He got a Princeton PhD working with Wigner. I think it may have been at a time when Wigner was doing other things but at any rate Jaynes didn’t — if he learned quantum mechanics, and I sort of think he did, because he really knows that kind of mathematics very well, but he has never believed in quantum mechanics. He certainly admits that it explains a lot, but he doesn’t like it. Philosophically he I suppose he’s suffering from the same kind of difficulty that Einstein had with quantum mechanics. And so he didn’t like the theory in which for instance Fermi worked it out, as I recall Fermi came up with an atom that is in an excited state, and then after a while it isn’t any more. The atom has been decaying exponentially. And so he worked out what would be the consequences in a theory in which you treated the coupling between the electron and the atom, but you didn’t do it using quantum mechanics, just using classical electrodynamics. And it’s not an easy problem, because you can’t even make a theory of an atom if you don’t have some quantum mechanics. So instead he took, he got around it, this shortcoming, in a way that I couldn’t accept.
So his work was not in any particular contact with what you were doing.
Well, his work is often called neoclassical theory, and it attracted a lot of attention from time to time, and there was, some of the Rochester conferences, some coherence dealt with problems of that kind. There was a famous occasion when Jaynes lectured on his theory and Peter Franken got up and holding a $50 bill and challenging Jaynes to a bet, that even after ten years there wouldn’t have been any experimental basis for believing this neoclassical theory. He was right. And after a bit of hesitation, Jaynes produced the money, and then they had to set up a stake holder, and that turned out to be me.
Yes. And I was appointed as the judge. My decision would determine which had won the bet. Well, then years went by, in fact eleven years went by, and somehow ten didn’t match the schedule of Rochester, the conferences, but eleven did, and I had to make a decision, and I decided that Franken was right. And so I divided the money. The accumulated interest, of course, had to be dealt with, so I subtracted what I imagined my income taxes on the accumulated interest to be, and distributed the remainder of the accumulated interest equally to the two contenders, and gave the $100 to Franken. Jaynes is still friendly. I don’t think his feelings were hurt. But he is deeply and philosophically opposed to quantum mechanics. But he’s a very bright guy.