How the Laser Happened

Charles Townes was born in Greenville, South Carolina, and attended Furman University. After graduate study at Duke University and the California Institute of Technology, he spent the years from 1939 to 1947 at the Bell Telephone Laboratories designing radar-controlled bombing systems. Townes then joined the physics department of Columbia University. In 1951, while sitting on a park bench, the idea for the maser (microwave amplification by stimulated emission of radiation) occurred to him as a way to produce high-intensity microwaves. In 1953 the first maser became operational. In a maser, ammonia (NH3) molecules are raised to an excited vibrational state and then fed into a resonant cavity, where (as in a laser) they stimulated part of the spectrum. "Atomic clocks" of great accuracy are based on this concept, and solid-state maser amplifiers are used in radioastronomy. In 1964 Townes and two Soviet laser pioneers, Aleksander Prokhorov and Nikolai Basov, shared the Nobel Prize. Since 1966 Townes has been at the University of California, Berkeley. 020