Being Coherent: Three Decades of Laser Development
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Being Coherent: Three Decades of Laser Development In»1916 Albert Einstein published a proof of Planck's law of radiation in which he introduced the phenomenon of stimulated emission. This phenomenon [It was first called "stimulated emission" in 1924 in a paper by J. Van Vleck] was the basis of the laser principle. Unfortunately, knowledge of quantum physics was then too primitive to put the phenomenon to any practical use. With the development of microwave technology during World War II, scientists turned to studying the interactions of microwaves with matter. This led, in 1952, to the first public proposal of a "maser." Joseph Weber, a young electrical engineering professor described the concept at the Electron Tube Research Conference in Ottawa, Canada. Interested in the idea, RCA asked Weber to give a seminar on the topic and paid him $50. The following year at Columbia University, Charles H. Townes, James Gordon, Herbert Zeiger, and their team achieved the first functional device using microwaves to create stimulated emission from ammonia molecules. Townes and his team of students supposedly went to a restaurant to celebrate their discovery and to brainstorm a Latin or Greek name for the device. When no one could agree on a name, they eventually adopted the acronym MASER, for microwave amplification by stimulated emission of radiation. Townes, who had been working for two years and had spent $30,000 of a grant on the project, faced detractors who translated the acronym as "Means of Acquiring Support for Expensive Research"! Three years later, working with Arthur L. Schawiow, a research physicist at Bell Laboratories, Townes proposed extending the maser principle into the infrared and optical range. Schawiow wrote, "October 1957, Charles Townes visited Bell Labs..:.and we had lunch...he was interested in trying to see whether an infrared or optical maser could be constructed, and he thought it might be possible to jump over the far infrared region and go to the near infrared or perhaps even the visible portion of the spectrum. He had some notes and said that he would give me a copy. We agreed that it might be worthwhile for us to collaborate on this study and so we began."
In July 1958 Townes proposed to the Air Force Office of Scientific Research that light amplification by stimulated emission be investigated. After eight months, Schawiow and Townes published "Infrared and Optical Masers," a theoretical paper that appeared in Physical Revieiv, December 15, 1958. This paper described their idea for a system that used potassium vapor instead of ammonia [as used in the maser]. A t first, the Bell Laboratories patent office declined to take notice of the invention, stating that "optical waves had never been of any importance to communications and hence the invention had little bearing on Bell System interests." But two years later, both men did receive a patent for their idea. Gordon Gould, another researcher working independently forTRG, Inc., also filed for a similar patent in 1959, which led to a long-running
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