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Lasers and Fiber Optics Essay




 

Charles H. Townes
Professor, Department of Physics
University of California, Berkeley

The laser invention happened because I wanted very much to be able to make an oscillator at frequencies as high as the infrared in order to extend the field of microwave spectroscopy in which I was working. I had tried several ideas, but none worked very well. At the time I was also chairman of a committee for the navy that was examining ways to obtain very short-wave oscillators. In 1951, on the morning before the last meeting of this committee in Washington, I woke up early worrying over our lack of success. I got dressed and stepped outside to Franklin Park, where I sat on a bench admiring the azaleas and mulling over our problem.

Why couldn't we think of something that would work at high frequencies? I went through the possibilities, including, of course, molecules, which oscillate at high frequencies. Although I had considered molecules before, I had dismissed them because of certain laws of thermodynamics. But suddenly I recognized, "Hey, molecules don't have to obey such a law if they are not in equilibrium." And I immediately took a piece of paper out of my pocket and wrote equations to see if selection of excited molecules by molecular beam methods could produce enough molecules to provide a feedback oscillator. Wow! It looked possible.

I went back to my hotel and told Art Schawlow about the idea, since he was staying at the same place. Back at Columbia University, I wrote the idea carefully in my notebook and had Schawlow witness it in preparation for the possibility of a patent. (In my previous career at Bell Labs, I had produced several patents in the field of radar and hence was familiar with patent requirements.) Soon my students and I began building the first maser—not yet producing light but demonstrating the principles. Its extension to waves as short as light came a few years later, after much excitement over the maser and as a result of my continued collaboration with Schawlow, then at Bell Labs. An essential element in this discovery, I believe, was my experience in both engineering and physics: I knew both quantum mechanics and the workings and importance of feedback oscillators.

When Schawlow and I first distributed our paper on how to make a laser, a number of friends teased me with the comment, "That's an invention looking for an application. What can it do?" To me, communications with a potentially large bandwidth and beam directionality seemed an obvious application. But the use of fibers did not occur to me, and that's what really changed communications, especially with the development of low-loss materials.

Lasers combine optics and electronics. And so in addition to their revolutionary role in communications, lasers by now have found a wealth of applications—in medicine, manufacturing, measurements and control, computing, possibly nuclear power, and much new science. Thirteen Nobel prizes have been awarded for work utilizing lasers or masers as scientific tools.

Both lasers and fiber optics are fields that can be expected to grow and develop further, including in ways still not foreseen. Consider that all of the separate principles and ideas involved in the invention of masers and lasers were known and understood by someone in the scientific or technical community at least as early as the mid-1930s. Yet it took 25 more years for these ideas to be put together to make a laser.  What might we be missing or overlooking now?


 


     Lasers and Fiber Optics
     Timeline
     The Idea
     Working Lasers
     New Applications
     Optical Fiber
     Gossamer Web
     Essay - Charles H. Townes





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