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I had tried two different techniques without success, and finally, Professor Rabi, who was a sort of guru — Dr. I. I. Rabi, one of the many Nobel Laureates to come out of Columbia — came back from Europe from a conference and he was all excited about what was called "optical pumping," using light from one source to excite another medium, in this case for the purpose of getting a population up in an excited state for making measurements. So he came back and said, "Well, I see you that haven't succeeded yet in what you were trying to do (which was to thermally excite [the molecules] — Why don't you try this?" So, being a lowly graduate student, next naturally I tried it. And that got me into optical pumping, and later on I saw how to use that, first to excite a maser — microwave amplifier — and then later on, laser media. And that was the beginning of it all.
So the beginning of it all actually had its start long, long ago, in some sense. To invent anything important or exciting, obviously you have to have a lot of building blocks in your head to do it. So if I say that on a certain night in November, 1957, suddenly, when I couldn't get to sleep, the idea for the laser popped into my head, the way to make that beam — yes, it popped into my head, but only after my head had been working away on all the materials for all those years.
Everybody who does anything creative at all has that feeling, that moment that happens from time to time, where suddenly something comes into your head full blown, almost, whether it's a painting or an idea for a book or a laser or anything else, or maybe a way of making money.... I believe that the mind has been churning away, subconsciously, on all the materials that are necessary to go into it. That stretched back to Yale, where I specialized in optics and spectroscopy there, Yale was a big optical laboratory. Columbia was not, but Columbia had all this microwave spectroscopy, and the maser was first thought of and demonstrated there by Townes and his students. It was really the combination of those things: familiarity with optical techniques, and also being in an atmosphere where all these new things were developing in the microwave area. That combination was needed to come up with something like the laser. Plus the added impetus of working on my thesis using optical pumping.