How the Laser Happened
Joining us today is a very distinguished guest, Professor Charles Townes from the University of California at Berkeley. He received a Nobel Prize in 1964 for his work in the fundamental physics of quantum electronics and he is also author of How the Laser Happened: The Adventures of a Scientist. Professor Townes received his PhD from the California Institute of Technology in 1939, thereafter he served in various positions at Bell Labs, MIT, and Columbia University before coming to Berkeley.
Frank Ling (FL) talks to Charles Townes (CT) on his work in developing the laser, astrophysics, and his views on science policy and education:
FL: Professor Townes, thank you for joining us today.
CT: Well, glad to be with you.
FL: So. I understand you started your earlier work with microwave radiation systems for spectroscopy and the radar. How did that lead to the development of the maser?
CT: Well, when I went to Bell Telephone Laboratories after getting my degree, I wanted to do science, but the war was coming along and very soon Bell Labs insisted that I should have to work on war problems, engineering problems. So I was assigned the job of designing radar systems, particularly for airplanes. I wasn’t very pleased with that but on the other hand, I knew that all of us had to pitch into the war. But it turned out to be very helpful to me. I learned a great deal of engineering and I learned about microwaves and I recognized then that microwaves could do a very good job of determining a spectrum of molecules and the characteristics of molecules and so on. So, I did that and pretty soon that was popular enough that I got invited to a professorship at Columbia University. I was glad to get into academic work. I continued such work in microwave spectroscopy of molecules. But I wanted to get to shorter waves. I was using waves about 1 centimeter long (half an inch long), I wanted to get down to shorter waves, down to a millimeter or half a millimeter or tenth of a millimeter because those waves would be absorbed by the molecules even more strongly. I would do additional science but nobody knew how to generate such waves. You see we made microwaves using celestrons and magnetrons that had been invented shortly before the war and during the war. They were all very useful but they could not get to short wavelengths. I tried and tried to get to short wavelengths and many different ways. And my students and I tried and nothing worked very well. I was even appointed chairman of the committee, a national committee to try to study how we could get oscillators to shorter waves and that committee traveled around and saw a lot of things, but we didn’t find a way. At the last meeting of the committee, I woke up early in the morning worrying about it, why haven’t we been able to produce shorter waves, I went through all my past thinking. Molecules of course oscillate very fast and produce short waves but you can’t get much energy from them, because certain thermodynamic laws and, hey wait a minute they don’t have to obey thermodynamics. We don’t have to have them at a specific temperature, we can have a lot of excited molecules and none unexcited, so wait a minute, hey that can produce strong energy. I quickly made some notes on a piece of paper and looked like it could be made to work. My idea was to get molecules in the excited state, having excess energy, send the beam into resonant microwave cavity, and then they would emit and then waves would build up in the cavity and take more and more energy from the molecules and that would make an oscillator – my students and I decided to pick out a name – we call it microwave amplification by the stimulated emission of radiation. As the microwaves amplify by the molecules which are stimulated to give up their energy as they had, we send in molecules with excess energy and that provides the energy. Now, I tried to make is work at first with about 1 centimeter wavelength because I had a lot of equipment in the centimeter wavelength. I really wanted to get down to a tenth of that or a hundredth of that, shorter wavelengths. I tried to make it work at first at the centimeter because I thought well I could work that way and then see how it works out. Well, it worked out really well and it was very exciting. And atomic clocks, for example very precise frequencies, much more sensitive than what we had before so that was an exciting field for quite a while. I wanted to get to shorter wavelengths and so I had to push the method.
Very few people thought that the maser, which was amplifying microwaves, could be made to get to shorter wavelengths. They thought you can’t have a lot of excited molecules at short wavelengths because they will fall down to unexcited states so quickly. They’ll lose the energy voluntarily so quickly that you can’t do this at shorter wavelengths. Yes, but I thought you can get to somewhat shorter wavelengths. But I sat at my desk and thought how short I can go. I wrote down some notes and equations and thought if we could feed energy into the molecules and then have them energetic molecules, which can then give up energy, how short wavelengths can we go to? And I looked at the equation and “Hey, wait a minute, looks like we can get right down to visible wavelengths.” Now that’s very short wavelengths. I wanted to get down to a millimeter. Now visible wavelengths are 20,000 times shorter than that. This looks awfully interesting and good. I wanted to get to the infrared, which is a tenth of a millimeter or a hundredth of a millimeter. So I talked to some of my students about it and I was consulting for Bell Telephone Labs at that time, and my brother-in-law Arthur Schawlow, was at Bell Labs and talked to him. I told him what I was doing, I though we could we visible light and he said well, I’ve been wondering that myself and well why don’t we work on this together so he and I worked on this together and we wrote a paper on how to do it and that was the laser. We first called it optical maser because it was like a laser but optics. Eventually it was called laser for Light Amplification by Stimulated Emission of Radiation. Some of my students wanted to call it IRASER, that’s Infrared Amplification by Stimulated Emission of Radiation. But IRASER didn’t last. So, we wrote a paper on how to do it. By then, everybody was so excited about the possibilities and a lot of people jumped in and try building it. All the first lasers were built in industry. Then that made exciting science and many people were using lasers and masers in physics and science as well as in engineering.
FL: And for the maser, it’s partly based on the photoelectric effect that Einstein had described for his first Nobel Prize, is that correct?
CT: Well, Einstein first pointed out that atoms and molecules give off energy and light and radiation and so on. There are two effects or two ways of giving it off. One, is they can just automatically give it off, that’s spontaneous emission. Or they can be stimulated into it by a wave of light or microwave, which tickles the molecule and stimulates it to give it energy and that’s a stimulated emission of radiation and Einstein first pointed out that effect was present.
FL: Looking back, what was it like to do fundamental research in the 1940s and 50s? Are there any differences with how research is carried out presently.
CT: Well, in general people continue to do research on the same kind of drive to find out new things and so on, but we keep finding out new things and those lead us on to other new things and we have new technologies, instruments and so on to measure new things we couldn’t measure before. For example, lasers and masers have been used as instruments to create another about a dozen additional Nobel Prizes. So if we didn’t have them, that kind of science couldn’t be done. Science continues to grow and multiply. It grows like a tree. You add on some and that adds on some more and that adds on some more. Science is in a way always the same, we are still exploring. On the other hand, it is also changing all the time because we are exploring different things, new things.
FL: So if we look at the current technology – lasers for cutting steel, laser eye surgery, security systems, and barcode readers – did you envision any of these applications when you first developed the science for the laser?
CT: I could envision quite a few applications, yes. Many people didn’t think it would be very useful but in fact I took it to a patent attorney and he said well what’s the point in patenting if you don’t see any uses for it. Now I could see immediately its use in communication and I knew it would be important in vision. In addition to getting a straight line, in addition to getting high intensity because you can focus the light, get very high intensity and burn things and so on. So, I could see number of applications but I could by no means see all of them. For example, a doctor came to me saying well I was wondering if we could discuss the possible uses of laser for medicine. I’d like to write a discussion in a paper on that. Would you help me on it and I said okay, alright, we’ll try to work together and write a discussion of how the laser might be used in medical purposes. So we wrote some things and made a number of suggestions, but he didn’t mention detached retina and I had never heard of a detached retina. So we didn’t mention that but that was really the first important medical application of reattaching detached retina. So, yes I could foresee quite a few things but by no means all of things that have happened. That is a characteristic of science, you foresee some things, you explore some things and then add on some more. We’ve seen a lot of really wonderful new things coming from laser.
FL: So speaking of high intensity, there was interest by the government to develop high intensity anti-weapons systems. Do you believe that’s a reasonable goal that deserves funding?
CT: Well, I think one should consider the use of lasers as a weapon, I don’t think it’s really a terribly good weapon however. It is very useful for military purposes for measuring things, checking things, and guiding things. For example, to make a missile hit the target: you hit a bridge instead of hitting a town and tearing things up unnecessarily. It very much increases the accuracy and precision of military instruments, but as a weapon itself, I don’t really think it’s very useful.
FL: So some have argued that the golden age of science ended in the 1960s at the height of the Cold War and since then funding has not kept up and research has not exactly expanded as quickly. Do you believe there is a problem? Certainly many of the technology we have today are based on the seminal discoveries made back then. Is our future threatened by the lack of funding?
CT: Actually funding of science has continued to grow. Science has continued to grow, but we are somewhat short of funding. More funding would be very helpful and I think it would help the country in it’s technology. But funding is not all that bad and science continues. It changes all the time. For example, nanotechnology is a fairly new field. In the 60s it was hardly present, now we can make things very small and work with things very small. Biology is also a fast growing field. Biology used to primarily descriptive, describing the behavior of animals and plants and how the looked and what they did. Now, we try to understand how they work. If we can understand how they work, we can control them more and invent new ways of doing medicine and controlling our own bodies and so on. So biotechnology and biology are fast growing fields. Science changes and continues to grows in large and the country is supporting it reasonably well, not as well as it should.
FL: In the popular culture, the laser is portrayed as beams of light that destroy spaceships and other objects. Are you amused by some of the ways that lasers are portrayed in the popular culture?
CT: Oh yes. I enjoy seeing that. Some of them unrealistic but they are imaginary and actually imagination is part of the growth of science and some of these imaginary things is not going to work out at all but it is fun to see them.
FL: In 1967, you came to Berkeley to pursue research in astrophysics. How did you become interested in studying the sky and what aspects of your earlier work in spectroscopy did you use for astrophysics?
CT: I might say first that when a field becomes popular that I’m working in, I think well they don’t need me to continue working in this, I think I’ll go do something that people are neglecting. So I move from one field to another from time to time. The laser field became very popular and I thought I don’t want to work with lasers directly cause I see some things in astronomy that I think people are missing and I’d like to work on. And one was infrared astronomy to make very precise measurements of spectroscopy in the infrared. I saw some ways of using lasers to make these measurements and I’m using lasers now to measure the size of stars, as a way of detecting the light coming from stars and using multiple telescopes in measuring the size of stars, watching them change in size and blow off material. I have a microscope in the sky developed. At the time, there was much of astrophysics that remained to be developed and it was interesting and I saw things that could be done and I’ve had a very interesting time trying to do that. One other thing I might say is that as a result of that we found masers and lasers in space. Masers and lasers have been out there produced by astronomical objects all this time. Nobody knew they were there. They have been there for billions of years. We didn’t have to invent them on Earth!
FL: Are these collimated beams?
CT: They are somewhat collimated. We don’t know exactly how much they are collimated but some of them are certainly collimated a bit, but they are very intense and it’s amplification of microwaves by molecules. They make very intense microwave light coming to us and water molecules in particular. There are also lasers up there, they are not so obvious but we find them though.
FL: So for the budding scientist, what advice do you have for them? Are there any particular fields they should look at these days?
CT: Well, I think there are many fields of science that are very interesting and I would suggest to anyone in any field to think about what they most enjoy doing, what you think is most interesting and important and drive towards doing that because the things you enjoy doing are the ones you do the best.
FL: I’m just curious. What are some of your earliest influences? Who are your inspirations?
CT: I was brought up on a small farm in South Carolina and my parents enjoyed the outdoors, animal and plant life and so on, and I became interested in natural history. I collected butterflies. My brother and I collected butterflies, insects, and snakes and we identified plants, trees, and so on. I waded in the streams and collected things there and tried to identify them. So I was very interested in natural history and the outdoors including the stars. So that was my initial interest in science to understand things further and further. My brother for example was an entomologist, went on to professionally collect insects, special kinds of insects. He had a very profound collection of parasitic wasps. I’ve collected some for him even fairly recently.
FL: I think we can argue that science eduction in the US, especially in the primary schools, is not very well taught. Do you believe this is a threat to our democracy? I know this is a very difficult questions, but what should we do about it?
CT: You are concerned about how well people are taught in the schools? Well, I think there is a wide variation as to how well people are taught in schools. Some schools are much better than others. Some teachers are much better than others. We do need very intelligent, interesting teachers in our schools and I think partly we ought to pay them more. We ought to respect teachers more. They are a very important part of our society. I had some very good teachers. When I was a youngster, women didn’t have many opportunities for jobs and many of the bright women went into teaching and they were good teachers. Now women can get many other good jobs and that’s a problem for our schools. I think we need to pay people more and emphasize the importance of schools more than we do now.
FL: Lastly, relating to the current election. This year has certainly been quite contentious. In fact, many scientists are concerned about the administration’s science policy. I understand you are one of the signatories of 48 Nobel Prize winners who support Kerry this year and also I understand that scientists are normally non-partisan, but what are your feelings on this election?
CT: Well, I support Kerry rather than Bush. Now the reasons behind that are many fold. So far as science has been concerned, Bush has not been very interested in science, has not been very appreciative of science, not very objective, and he has gotten advice from scientific groups which he has not paid too much attention to. And he wants scientists to give him the advice that he wants. Another thing is I think Bush has made some very bad mistakes internationally. I think he is hurting the United States in relation to other countries. It’s trued Iraq had great difficulties and it would have been good to replace the leader of Iraq as Bush succeeded in doing as an international cooperative thing and people would have understood the situation much better. I think we should have insisted on making it international. As it is now, it looks like the United States is doing all of this and we’ve antagonized the Moslems and we have to turn that around. This must be a helpful world where one country helps another and people recognize that. The United States used to look more like that and now internationally we look very badly.
FL: On a related issue, Russia recently signed the Kyoto Protocol which this administration has rejected since they came in. Do you believe there is now more pressure to adopt the Kyoto Protocol or a similar policy?
CT: Oh yes, I think we need to control greenhouse gas emissions. It’s not going to be easy but we need to work hard on it and that’s something that Bush has not been willing to push very much on. It is important in the long run. We also need to concern ourselves with the use of energy because we will be using up all of the oil and coal in a finite time and most of it will be gone. We’ve got to find new sources of energy and we’ve got to be able to control the greenhouse gases and so on. We need a lot of work on that.
FL: You’ve given advice to many presidents throughout the years. What exactly is the role of scientists in the political arena?
CT: Well science is very important to our civilization and to our lives. We depend a great deal on science and technology and it is becoming more and more important all the time. It’s important for society to understand something about science and technology. But some of it is pretty difficult and so politicians badly need advice from objective scientists who can think hard about what’s best for our society and what’s likely to happen scientifically. Many politicians recognize that need the advice of scientists because they can not understand science as well as they would like but they all ought to understand it as well as they can. I think all of our people need to try to understand science and the future of science because that will affect our society enormously. It already has and continues to do so. I hope there can be more science education for young people.
FL: Professor Townes, thanks for joining us. Thanks for your time.
CT: Well, I’m glad to be here. Best wishes.