Oral History Transcript — Dr. Aleksandr Prokhorov
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Interview with Dr. Aleksandr Prokhorov
Aleksandr Prokhorov; September 14, 1984
ABSTRACT: Work at Lebedev Physics Institute; study of radio-wave propagation interrupted by World War II; returns to Institute after being wounded, begins study of nonlinear radiophysics; synchrotron radiation in microwave region; starts accelerator group (Nicolai Basov)i switches to microwave spectroscopy (Charles Townes, Walter Gordy), 1950; ruby crystals (Dr. Manenkov); Prokhorov proposes use of interferometer; gas-dynamic CO2 laser, 1966. Commercial application of lasers in USSR future laser applications.
Guenther:Testing ... this is an interview with Academician Prokhorov in Moscow at the General Physics Institute... 14th 1984. In presence besides Prof. Prokhorov, is Prof. Malikov of the same institute, Prof. J. Thompson of the University of Texas at Arlington, and Prof. A. H. Gunther the interview for the Laser History Project. The interview is, starting at 0945 in the morning. We would like to start off the interview by asking about the environment at the Lebedev prior to the time of your work in the early days; what kind of resources, budget, professional staff, technicians, etc. for your research were available? Did most of the communications among researchers take place at formal seminars, over luncheons, or in what manner? Were you on a seven-day week, even schedule, or a more relaxed schedule? And who were the key members of your group? For example, the molecular spectroscopy group? And what were their special areas of expertise?
Prokhorov:(In English) Yah, I started my scientific work at Lebedev Physics Institute in Moscow. It was little, not so big, about one hundred people total, very small one. And I started to study, in that period, by radio-wave propagation. And I did till 1941. Just before the war, Second World War. And from 1941 to 1944 I was in Red Army in the field. After been wounded, I returned to Lebedev Physics Institute. This was a heavy time for us. Because the war was continuing. And I began to work with nonlinear radiophysics. Because the only field I can do, because we have no much resources and so on. And I ... 1945, I took Ph (sic) degree. It is the first step for the official degree in our country. It is mean kandidat nauk (candidate of sciences), Russian. In 1948 I began to work in the field of new type of oscillators. With Prof. Veksler who first…who first invented new type of accelerator –- a synchrotron radiation in microwave region, for the first step in or degree, it’s Doktor Nauk (interjection – Doctor Science) Doctor of Science, yah. After when I finish this work I had a group, mainly consisted from students and between them was Dr. Basov, who is now no surprise that everybody knows (Interjection — how many were in the group?) About seven persons (interjections — seven students?) No. five students and two scientific staff. (Interjection — and who was the other person on the staff?) Barchukov, Irisova, Osipov…you see that…and other one with…I will remember it, yah. And after I have finished, after 1949 or 1959, I decided to switch my fields with other group to another problem — microwave spectroscopy. The microwave spectroscopy, at that time, was developing in US and England. There was many papers about this subject. (Interjec. — Who were some of the workers that you followed in these other countries?) Other countries? Ah, Bliney (?) I know from US and Charley Townes from US, mainly, and also Gordy, Walter Gordy (interjec. — at Duke University?) Yah, Duke University, yah. But there are other people, of course. And we had some papers in this field, and my group was increased: Manyukovkin, Konyukhov, Murina, Karlov, Mikhelaga were students which come to my research group and we worked in the field of microwave spectroscopy. (Interjec. — And many of those people are still working with you today.) Yeh, and other people which started with me with accelerators also work with me — Dr. Basov and so on. Starting the microwave spectra, we wanted to increase resolution, to resolve hyperfine structure. And, of course, this can be done by using molecular beams, because you can include collision, and Doppler effect. And as we obtained... if you obtain a molecular beam, now understood that we can obtain molecules only in upper states, no this was done before using molecular and atomic beams, it to have all atoms or molecules in upper state. And then understood that it can be used in such media, can be used as amplifier. And I, together with Basov, put effort in developing such devices. To obtain amplification, also oscillation. And we understood at that time that such device can produce monochromatic oscillations, it is a very important step. Because not only amplification but you can obtain monochromatic sources. And nobody did before it. Because before this you see that you can [can't ?] amplify. And this was very important point, and some people didn't understand at that time that it is possible. (Interjec. — Now about what year is this that we are talking about?) Sorry, in 1959 in Cambridge in England I gave a lecture, a paper about the theory of laser. For the first time I showed that this (disc?) device, theory of this device, from you see, as radiophysics. At that time, yes, at that time also was maser done by Charlie Townes and his colleagues. We are parallel in our development, such deal only with molecular can we obtain population inversion in gases for instance. And we offered with Basov a three-level system by pumping. Nika Bloembergen did a very important step that we — Dr. I and Dr. Makinkov — proposed ruby crystals for such devices. It was (interj. — for masers)… (Interj. — What was the quality of the crystal growing at that time, for what size…) For masers it is quite good. For lasers, it was not so very good, at that time. And we developed such devices using ruby crystals for practical things as for astronomy, for observing monochromatic sources in our space, and they use it also now. A maser was developed, everybody dreamed about lasers, of course. As now, everybody who deals with lasers dreams about x- and some gamma rays. And what we were to do important problems to solve (and what we were to do to solve this important problem)? To have…to develop the laser. There were two difficulties to develop the laser. At that time no resonators for the optical wave region were available. The second difficulty was no method was immediately available for gaining inverse population in the optical wave region. You see, if you wanted to use cavities which I am using now in microwave region, then when you go to the optical wave region with the dimension of the cavity, which may become terrible with welding, be very small. With no practical using, it's no practical importance of the sectioning. And if you ... and in many books and papers it was written that we don't know how to solve this problem, because you can't use resonators which are... which we used, are using now, also at that time, for microwave region. And I proposed in 1958, I proposed an open-type of cavity for masers and lasers for the very short waves. But now it is known as Fabry-Perot interferometer. But nobody didn't know that this can [can't?] be used as a resonator. (Interjec. — Were you thinking principally of a plane…) Yes, plane, only plane, only plane, yes, that's right. And now we have different type of such open resonators, of course. But you see, at first, many people didn't believe that this type of resonator can work as a resonator. But I and Barchukov have demonstrated the possibility of such a resonator in a millimeter-wave region. We demonstrated experimentally that this type of resonator works. Sorry, but now I ... maybe we have interrupted ... our self and I can think little bit more and then we shall... [Translator: He says let's take a break.]
Guenther:One of the things that we're doing in the history for the people of America is to find and describe the environment. Now I think you have done a very good job in describing your environment here at the Lebedev in the work you led up to here. I sense from what you've been saying that the prime mover in this was to develop microwave amplifiers, and systems like this for applications in radar and things. Were there other things people were interested in that they saw that this work would apply to and encourage you to work along these lines?
Prokhorov:(in English) Yes, you see what I can say, you see when masers and lasers were developed, they were unusual devices, and the industry engineers didn't understand this type of devices. Quite unusual. And, therefore, we gave many seminars to teach these people, show them the lasers and masers in our laboratory, and so on, and so on ... (American interjec. — To describe the potential applications.) Yes, of course, I think so... not more... physical basis of such devices [someone interjecting in English — "background"] ... background, you see, you just start with this, then you can understand what type of application can be...
Guenther:What you're saying — you taught them the physics and it was to them to see what the application might...
Prokhorov:... they must see themselves. Yah, we have divided...
Guenther:Yes, o.k., well was there any interest from the military in this research?
Prokhorov:Yes, of course they have interested one but we have very new contact with them because we can't give them any good advices to application, for radar of course it's quite obvious, they nothing scientific...
Guenther:You see much of the funding for the early work in the US came from the military to develop masers and microwave amplifiers, what was...
Prokhorov:... For radar, but not for us because we do, how to say, only physical side, we don't develop them radars and so on, we didn't deal with such things and, therefore, we have practically no contact with the military. But they support the industry, of course.
Guenther:They support industry so the transition would be your research, giving seminars to the industrial people, they would then see that this has an application, just like military research, and they would interact directly with the military (Translator: Throughout this sentence Prokhorov has been saying “yes…yes…yes…"). Would this ever then come back down to you? No, just industry, we have only with industry, because we do nothing, we don’t do practical devices for them and, therefore, they need no contact with us. I want to go back to one point that you discussed earlier which is…you became familiar with the work of Bloomberg and Scolville (?) and that primarily from the journals, do you recall what journals this was that you were reading at the time, that made an impact upon your work?
Prokhorov:I think so... Pizdarev (?) Pisarev (?) He was more popular Pisarev (?). At that time [several voices joining in].
Guenther:And the principal conference was this conference you mentioned in Cambridge...
Prokhorov:Yes, but only one paper about masers, my paper at that meeting.
Guenther:Were there any other conferences that you interacted with these people...
Prokhorov:Yes... no... Quantum electronics conference in 1958, that was first quantum electronics conference and there was a paper... I... my paper was about ahhhh... open resonators in 1958 (garbled)... in fifty nine, which was organized by Charlie Townes. It was a very small one, a very good one.
Guenther:Could you tell us how you came to... upon the idea of three-level masers using pumping?
Prokhorov:It is difficult to say because you know we are thinking about can we obtain by another scheme, scheme pumping, you know to obtain... and it is difficult to say because... suddenly came idea, that all.
Prokhorov:Well, thinking very hard, you see, you know if you think all day and night and so on sometimes, good idea comes to you, not every time, of course (laughs).
Guenther:But the light comes on.
Prokhorov:Yes, light comes on (laughter), that's right.... you know, when I was on holidays, I also think about it, nobody disturb me, nobody ask me about nothing, and I can think without any trouble.
Guenther:You can draw pictures in the sand.
Prokhorov:Yah, and surprised (?) (laughter).
Prokhorov:You see, good ideas come to me when on holidays. When nobody disturbs me. You see my wife tells not to disturb me and she doesn't disturb also (laughter).
Guenther:Can you say something about how you interacted with the coworkers that you had here at the Lebedev, and the types of theories that you were employing at that time... that related to lasers and masers, and, and something about the balance between theory and experimental work?
Prokhorov:Yes, you see when I came to work at the Lebedev Physical Institute I dealt mainly with theory. Because we have not good equipment to work due to the war, of course. But, myself, I like experiments and, therefore, after I came to deal with microwave spectroscopy, it was possible to obtain all kinds of devices, klystron, and so on to deal with my specialty and, therefore, I switched myself mainly to experimental work. But I also did a theory, you see, for a three-level system, can we, obtain good time... [says in Russian - "I'll say it in a second...] hmmm how to say ... standard frequency (interjection - frequency standard), frequency standard using three-level system by [word is unintelligible) pumping, you know I showed that it was not a good system (another Russian interjecting - for this particular maser as a ... as a stable..." frequency stable... )... frequency stable, yes. Sometimes I do some theoretical work but mainly I deal with experimental work, I like it.
Guenther:Did, did... How you worked yourself change over the years as your positions changed here at the Lebedev?
Prokhorov:You see I work, I also like to work in laboratory, depending on my position. I try to have, you see I have good relations with scientific groups, with my colleagues no matter what position I hold, because in scientific research there are no bosses, you see, there are same opportunities and the same possibilities, I should show to discuss everything (?) .
Guenther:I think you said something very important when you said in Scientific Research there are no bosses...
Prokhorov:...no bosses, yes.
Guenther:Every must question exactly.
Prokhorov:Yes, that's it exactly. You know, if you have bosses in scientific research, there will be no good scientific discovery. And you microwave switches very easily from one thing to another, you see, we deal with microwave spectroscopy — it is a radio-wave region — then we switch to lasers, everybody switch with me to lasers, and now we deal with other things — solid-state physics and so on, and everybody also switch [unintelligible].
Guenther:What you saying is that people went where the action was...
Guenther:... where the excitement was, where the newness was.
Prokhorov:Yes, yes and they are not afraid to go in new field, and that's very important.
Guenther:Going very good, we just finished first half of the tape, and we're easily through half the questions, so I think we’ll finish in another 30 min.
Prokhorov:I believe it (laughs).
Guenther:Let's continue, where you continue describing your thoughts and recollections, back at the resume bracket, I guess (?).
Prokhorov:Yes, I know, I think so ... I must continue another statement that very important step in development of laser were done by A. Schalow and Townes. In the famous fundamental work about laser which was published in Physical Review. This paper gave great stimulation to laser Development. The first demonstration of laser action was done by Theo Maiman, using ruby crystal. That's very interesting one that Maiman, and myself also tried to do the same thing, I think other laboratories and other scientists tried to do the same.
Guenther:They tried to do it before.
Prokhorov:Before Maiman, of course, before...
Guenther:But it wouldn't work?
Prokhorov:No, because we didn't have this final step, we were only on the way to this research…
Guenther:How did you hear about his laser…
Prokhorov:Also, also from news... from... Nature, I think so, yah. Nature, we didn't have a direct contact. Only by magazine, yah. But as we have ruby and good scientists and we have... in our country, we repeated this work. We have to improve little bit, the quality of the ruby crystal. The ruby crystal was prepared in the Institute of Crystallography of the Academy of Science.
Guenther:So, you repeated the experiment after?
Prokhorov:Yes, afterwards, yes after...
Guenther:But you have tried before, also?
Prokhorov:Yes, we knew that it could be done, in general, but you see, idea is one thing but how to do it is another.
Guenther:What problem did you have?
Prokhorov:Pumping problem, pumping problem... (another Russian interjecting — you need a good ... pumping problem ... quality...) ... yes ruby and pumping problem. You see, what we didn't understand, you know, the quality of the crystal and so on. There were many problems, you see... and we have no many opportunities maybe as Dr. Maimam had, I don't know why...
Guenther:Do you know what technique was being used to grow the rubies at that time?
Guenther:Vernov (?) .... not Chekhrovskiy (?).
Prokhorov:No, no, no... (another Russian interjecting — at that time only process.)
Prokhorov:Yah, yah, yah and Chekhravskiy afterwards, yah. That's an interesting thing, but you see, it happens quite often when you lead, sometimes you're ahead. I think another very important step in laser field is how to obtain a very high-power laser? Everybody tries to obtain a very high-power laser. And I and Konyukhov proposed gas-dynamic CO2 laser. We didn't write that we can't obtain high power because it is to calculate rather primitively, and Gerry (?) from US has demonstrated that one can easily obtain 60 kW CWX.
Guenther:About what time did you come up with this idea.
Prokhorov:(speaking in Russian): When, right now I can't remember. (Speaking in English) But he referred to my paper, Gerry, to our paper.
Guenther:Name is Gerry (someone interjecting - Jerry).
Prokhorov:Yah. At what time I don't know precisely. (Looking through papers, mumbling...)... 1966, yah. But you know, CO2 lasers are now being used widely in different regimes, for different purposes, and we also have to mention that Battelle was the first who proposed this type of CO2 laser. It is also very important. Now understand that semiconductor lasers are also important. And this theme will be discussed by Prof. Basov, who deals with this field, and I give him this opportunity to discuss it. Very important step also was done by Aligevany's (?) coworkers in developing gas-discharge laser. He was first (to develop) gas-discharge laser — neon laser, and he demonstrated the action of such a laser.
Guenther:And, again, you heard about that work through the literature.
Prokhorov:Only through the literature, yah.
Guenther:There was no written communication?
Prokhorov:No, no, no, that's right. You see, that's bad and good. Mainly it's not so good but you have some positive and also negative side of such thing. I think so, maybe, it is enough for lasers, yah?
Guenther:Let me just ask a few other questions...
Prokhorov:(unintelligible) ... multiphoton apparatus (?)
Prokhorov:Yah. You see, in our lab, Dr. Pashinin (says in Russian — you write, Dr. Pashinin) obtained a gas-breakdown laser, who was not the first, of course, it was done, I think, in US or Canada, I don't remember exactly.
Guenther:It was done early in places, Terhuin (?) did it...
Prokhorov:Terhuin, yes we have to mention also Terhuin because he demonstrated that you can obtain, yes that's right, we must start from Terhuin's experiment, he obtained giant pulses from that laser, and it was very important, and using his technique, one can easily produce gas breakdown. And Dr. Pashinin measured the electron temperature for the first time, it was about 1 keV, something like this, he was the first to obtain such things. But why does breakdown occur? Over avalanche process and by other mechanism, and we proposed with Prof. Bunkin (?) Bunkhin that it is a multiphoton absorption; and we gave a paper about this process — it was shown that this can occur. But the best paper was done by Prof. Keldysh (?) and he showed...
Guenther:Classic paper? Classical paper, that's right, that's right, he showed that it can be multiphoton or tunneling effect. Very important paper. But you see it came only from our country, such approach, both papers.
Guenther:I also noticed, if I may state that Prof. Pashinin then spent some time in Canada?
Guenther:And continued work along air breakdown.
Prokhorov:— yah studies with shock hydrodynamics — yah so there was that kind of interchange taking place.
Prokhorov:— yah, were there any western scientists that came over to the Soviet Union at this time and interacted with your group?
Prokhorov:Yah (another voice — "latter on") latter on, yes. But not very much. [Trying to recall in Russian] ... Richardson ...
Guenther:Richardson came here for a while from Canada.
Prokhorov:Yah, yah from Canada, and I think so, it is very important to have a good contact because you know that the science is so complicated and every scientist has a different approach to the same problem, and when you interact, you choose the best solution, and it is very important that such a contact must be, from our side, we would like to have a good contact. Every scientist, from every country, yah.
Guenther:It's getting very close here to the end.
Prokhorov:Yeh (laughs), that's good...
Guenther:Ah, can you say something about the development of the maser and laser community within the Soviet Union and what new research groups were set up in universities or institutes during the fifties and sixties, and any new journals that came out specifically to address, you know, quantum electronics and...
Prokhorov:No... quant.(?)... you see, [Trans: He is speaking in Russian, the third word is unclear, I think he is saying "just repeat this only and nothing else"]... about journal with only quantum electronics...
Prokhorov:Soviet journal, quantum electronics. But everybody in our country, every research institute, physics institute, every university where there are many physical... physics was excited by lasers, and in our country it spread rather good, for instance, in Moscow... (another Russian interjecting in Russian — "conference should be mentioned.")
Prokhorov:(says in Russian) — "wait I... and continues... in Moscow University, for instance, Prof. Khokhlov has developed many nonlinear effects in optical region using a laser, but... it's very important development in this field. I also have to mention Franklin...
Guenther:(interjecting – Peter Franklin)
Prokhorov:...Peter Franklin, who obtained, for the first time, second harmonic radiation in the optical region, it is also a very important step, it's from US. And now lasers are being used very wisely in many institutes, many universities for the research. And, we have many conferences... we have internal conferences but we also... ah... [asking in Russian how to say invite]... invite some foreign guests to take part in this conference. And I think it is very important. And they come especially to take part in our conferences; we also go to other countries and also take part in these conferences. Especially in international conferences.
Guenther:We have been asking the people in US how commercial applications of the lasers have influenced their scientific work, and I think we hear you say that that's primarily carried out in the industries if... from this as a basic research, do you have any contact with ministries to help them in the development of commercial products or commercial applications of lasers.
Prokhorov:You see, what I can answer is this, first of all, we are also interested to have commercial laser, in order to do research it is better to have laser from industry than... it is possible, of course, to produce itself but on the other hand we, of course help them because, well, one good example: you know YAG crystal is very popular now in the whole world, but in our institute Osiko (?) developed new crystal — gallium-gadolinium-strontium-garnet. There is no such crystal in US. It grows very quickly — ten time quicker than YAG; the efficiency is, something like, three times higher, and what we did? We gave this technology to our industry and they now grow the crystals.
Guenther:So, again, it's something that was developed here and given to them.
Guenther:It is not them coming and saying, "we need something to you?"
Prokhorov:Sometimes they ask also, yes. But see, what I can say, we did not I (unintelligible)... crystal and we... you see they can ask us everything, you know sometimes they ask but sometimes we... impossible ...
Guenther:How does (sic) their requests or their needs or desires get... become known to you?
Prokhorov:Oh, they come to me, for instance.
Guenther:This more on the same question. In the West many types of lasers — carbon monoxide, dioxide, iodine, solid-state, electrodynamic, gas-dynamic, and various CW-pulsed and repetitive lasers have all been developed, and many of these have developed because of specific commercial applications for industrial uses: for metal processing, (unintelligible) processing, and what not, and is there any comparable drive to develop laser systems in the Soviet Union based on these specific applications?
Prokhorov:But not with us.
Guenther:Not with you.
Prokhorov:But sometimes, you see, for medical purpose, you see, we do it, you see about ten years ago Dr. Krasnov came to us, he deals with eye disease, (interjection — ophthalmology) yes, and he said what can laser do to cure... (asking in Russian: how do you say in English ... )
Prokhorov:Not cataracts. (another Russian interjecting - just a moment, glaucoma)... glaucoma, yes, can be used for glaucoma... the answer was easy he said that if you want to have a hole, you know, to go liquid through it, and it's the only way not to have thermal effect... without using too much energy you can use laser to drill a hole, and we developed it and he used it successfully. (Another Russian interjecting — in our laboratory.) Dr. Maninkov deal with such problem and he developed such laser and gave to him, and it...
Guenther:Where is this doctor come from? Is he from some... (another Russian interjecting — he is a director of the Medical Research Institute)... yes, and now in the west countries everybody sees that switched laser (?) is very good for ophthalmology. But it was done ten years ago, something like this. Sometimes we do you see, but...
Guenther:If these people... if the people who require the lasers for various applications don't come to you, who do they go to to make these developments?
Prokhorov:Yes. If they have some question, they come to us.
Guenther:The industry comes to you?
Guenther:O. K. What capability does industry have to answer questions of that sort? Do they have PhDs and people trained in optics?
Prokhorov:Yes, yes, yes...
Guenther:Can you give us an example of an industry that would do that?
Prokhorov:You see, in every part of industry we have such (unintelligible), we have no special industry, we do not have special firm or company.
Guenther:These are government institutes that produce industrial products.
Guenther:One thing because the laser has developed so rapidly, in its application to many areas, we have found that there is a need to train not only professionals but to train technicians in this area so that they can install lasers, maintain lasers in systems and to work in research laboratories, and how is the training of laser technicians handled to service your needs here and as well as to serve your industry or the people who use the lasers, how are these people trained? Are there special schools? Are they trained in industry?...
Prokhorov:No, no ... (something on Russia unintelligible in Russian) ... you see we (unintelligible)...
Guenther:That's the professionals?
Prokhorov:Professionals, yes. And they give lectures for industry also, to train them, yes. And industry they have also such training. We don't do, our institute ...
Guenther:No, but you're saying that training of technicians are (sic) done by industry?
Prokhorov:By industry and by higher schools.
Guenther:High school? (Translation: he means higher schools)
Prokhorov:Yes, to some extent... (interjection: universities) — yes, universities (Another Russian interjecting — at Moscow university, a special course in quantum electronics for industrial people).
Guenther:Industrial people; that are not necessarily professionals, they are more technicians. (Another Russian — not only technician, professionals too.)
Guenther:And what's the difference in the number of years they might go to school for this? How much education do they have — the difference between the professional and a technician person?
I don't know (in Russian — "I can't answer this").