Charles Hard Townes

Charles Hard Townes, born in 1915, American physicist and Nobel laureate. Townes made important contributions to the field of quantum theory and significantly improved radar technology. For his fundamental work in the field of quantum electronics, Townes was awarded the 1964 Nobel Prize in physics, which he shared with Soviet physicists Nikolay Basov and Aleksandr Prokhorov.

Born in Greenville, South Carolina, Townes received his B.S. degree in physics and modern languages from Furman University in 1935. He went on to obtain his M.S. degree in physics at Duke University in 1936 and his Ph.D. degree in physics at the California Institute of Technology (Caltech) in 1939. From 1939 to 1947 he worked at Bell Telephone Laboratories. From 1948 to 1961 he taught physics at Columbia University, and from 1961 to 1967 he taught at the Massachusetts Institute of Technology (MIT). In 1967 he became a professor at the University of California at Berkeley, a position he still holds.

At Columbia, Townes studied radar technology, which involves emitting and receiving microwaves—the wavelength of electromagnetic radiation that falls between infrared waves (see Infrared Radiation) and radio waves. During his studies, he recognized the need for a device that would generate microwaves in great intensity, and in 1951 he came upon the idea of producing this energy by manipulating molecules rather than electronic circuits. Townes immediately thought of the ammonia molecule, which had a vibrating frequency and two levels of energy that might lend themselves to producing microwaves. He hypothesized that he could get ammonia molecules “excited” by pumping energy into them through heat or electricity, after which he would expose them to a weak beam of microwaves. Townes knew that molecules so treated would emit their own energy in microwaves, which would strike other molecules and cause them to give up their energy. He hoped that the very feeble incoming microwaves would spur a cascade that would produce a flood of microwaves.

In December 1953 Townes and his students constructed a device that did exactly this, producing microwaves in a beam. They dubbed the process “microwave amplification by stimulated emission of radiation,” which led to the more commonly used term maser. The maser quickly found many applications for its ability to send strong microwaves in any direction. The new device resulted in improvements in radar and also provided the basis for an atomic clock that was far more accurate than any mechanical timepiece ever invented. In the late 1950s Townes and his associates improved upon the maser by creating solid-state (see Condensed-Matter Physics) masers that could amplify (see Amplifier) ultraweak signals better than any other known means of amplification. In 1958 Townes developed the concepts for the visible-light maser, or laser (derived from “light amplification by stimulated emission of radiation”), which delivers infrared or visible light instead of microwaves. Two years later, American physicist Theodore H. Maiman built the first laser. Throughout the rest of his career, Townes's primary interest remained quantum theory, but he also pursued research in radio and infrared astronomy.