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Laser pioneer reflects on making Einstein’s idea real

Q & A with Charles Townes

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12:22pm, April 23, 2010
Magazine issue: Vol. 177 #10, May 8, 2010
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The laser celebrates its 50th birthday this month. Charles Townes shared the 1964 Nobel Prize in physics for his role in the laser’s invention and at age 94 remains active in research at the University of California, Berkeley. Townes spoke about his life in science and the events leading up to the development of the maser — the laser’s microwave cousin — and of the laser itself with Science News reporter Ron Cowen.

In what way did your experience growing up foster your interest in science?

It had a very big influence. We lived on a small farm in Greenville, S.C., and we had to do our own chores and make things work and that was a hands-on experience that [later] was quite important for experimental physics. I was interested in anything and everything, especially natural history and the outside world, and that’s thanks to my father. He would bring home clocks and other gadgets for us to take apart and see how they worked.

Einstein described in 1917 the concept of stimulated emission, which is the basic principle behind the laser and its predecessor, the maser. So why did they take more than 30 years to develop?

The laser and maser could have been developed much earlier. It took time and the right mix of people and events.

After World War II, the military was very good at allowing scientists to explore and expand new fields.... In my case, I was working with microwaves during the war, doing the work on radar, and I recognized that one can do very interesting spectroscopy with microwave radiation, studying the structure of atoms and molecules, if you had an intense source of the radiation.

To develop the maser, we somehow had to get more atoms in an upper energy state than the lower state. At Columbia [University], people were using atomic and molecular beams to separate various energy states. I knew about the work and recognized it was one way to separate and trap atoms in a higher energy state and make a maser.

Several people at Columbia in the early 1950s, including physics Nobel laureate I.I. Rabi, told you that trying to build a maser was a waste of time. What made you disregard that advice?

I’m accustomed to being myself, being independent, and that’s a very important part of creativity. My parents taught me that, too. Don’t do what other people are doing; you do what you think is really right. I had to think about what these people were saying, yes, but it wasn’t troublesome or upsetting when someone disagreed with me. Luckily, I had tenure at Columbia. If I didn’t have tenure, that would have been a bigger problem certainly, whether I would have taken a chance or not [to build the maser], I’m not sure. After we built the maser, Rabi didn’t exactly apologize, but he did congratulate me on my work.

Once you and your colleagues developed the maser, what made you decide to refocus your efforts and try to develop the optical analog — the laser?

I first tried [making an amplified beam] in microwaves because I had microwave equipment and that was the easiest way to do it. And that was so exciting that everyone got interested in it. We were doing very successful spectroscopy and finding out a lot of things about molecules and atoms and nuclei and so on using the maser. But my primary purpose was to try to get down to shorter wavelengths than microwaves, into the infrared and light waves. And I wanted to do that because I saw there were new kinds of spectroscopy to be done there. Everyone was familiar with light waves. After some analysis, we [Townes and his collaborator, brother-in-law Arthur Schawlow] wrote a paper that covered all of that.

In the early 1980s the Reagan administration embraced the idea of a system of lasers powerful enough to destroy nuclear ballistic missiles, a program nicknamed Star Wars. What did you think of that program?
 

Initially, the laser wasn’t thought of as a weapon but pretty soon after it began to be developed, it was examined by many people as a possibility. I think some unnecessary money was spent [on Star Wars], even though we did need to explore the idea. But some people were overly enthusiastic and were convinced it would work. It never worked, and I didn’t expect it to work. And I said that I didn’t think it would work. It’s more feasible now, but we also recognize more clearly how difficult it is to get enough directed energy [into the atmosphere] for such a system. We can get somewhat close but we can’t quite do it. 

At age 94, when most people have long since retired, you’re still doing research, using laser technology to measure the sizes and shapes of stars. What keeps you going?

It’s such fun. I have a great time with it, so why stop?

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