Townes, Charles Hard

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TOWNES, Charles Hard

(b. 28 July 1915 in Greenville, South Carolina), physicist and engineer who dedicated his life to applications of microwave generation and amplification and invented the maser and its optical descendent, the laser.

Townes was one of two sons of Henry K. Townes, an attorney, and Ellen Sumter Townes, who helped run the family farm. He attended elementary school, high school, and Furman University in Greenville, graduating with a dual bachelor's degree in physics and modern languages in 1935. Townes finally left his hometown to attend graduate school, obtaining a master's degree from Duke University in Durham, North Carolina, in 1936 and a Ph.D. from the California Institute of Technology, in Pasadena, in 1939, both in physics. He would have liked to go straight into academia, but given the depressed economy, he was grateful to get a job with Bell Telephone Laboratories in Murray Hill, New Jersey, earning $3,016 a year. Townes married Frances H. Brown of Berlin, New Hampshire, in the spring of 1941, and the couple had four daughters. He continued to work at Bell throughout World War II, focusing on the development of radar bombing systems; his findings eventually were incorporated into the B-52 bomber. As radars were shifted to shorter wavelengths, they became less effective; Townes discovered that the radar energy was being absorbed by ammonia and water vapor in the atmosphere. This led him to investigate microwave spectroscopy.

Townes joined the faculty of Columbia University in New York City in 1948 and soon obtained a grant from Union Carbide to do research into microwave generation. In April 1951, unable to sleep, he had an inspiration: "One should be able to put enough excited … molecules through a cavity to produce an oscillator.… The signal, I also knew, would be coherent." It took him three years to turn his vision into reality, amplifying and generating microwaves in ammonia gas by stimulated emission of radiation. He coined a term for his process: microwave amplification by stimulated emission of radiation, or MASER.

Microwaves vibrate with a relatively long wavelength—Townes was working at 1.25 centimeters, or half an inch; to achieve the same results with energy in the visible wavelengths would require working with waves only thousandths of an inch long. Nevertheless, in an article in the December 1958 issue of Physical Review, Townes and his associate Arthur Schawlow showed how their maser could be transformed into an optical maser, or laser. They applied for, and received, a patent for their invention on 25 March 1960, just about the same time that Theodore Maiman of Hughes Aircraft Company built the first practical laser. In 1964 Townes shared the Nobel Prize with Aleksandr Prokhorov and N. G. Basov of the Lebedev Institute in Moscow, who had independently envisioned a similar method of microwave amplification shortly after Townes's inspiration.

Townes moved his academic affiliation to the Massachusetts Institute of Technology in 1961, serving as provost for five years. During this time he also directed a special session on coherent light at the Enrico Fermi International School of Physics in Varenna, Italy, and delivered the Scott Lectures at the University of Toronto. In 1967 he became a professor at the University of California at Berkeley; his research interest since then has been the application of quantum electronics to astronomy. He became professor emeritus in 1986.

One of the highlights of Townes's career occurred in 1969, when the Apollo 11 astronauts placed reflector panels on the moon and astronomers from the University of California and the University of Texas bounced laser beams off the panels and back to Earth, measuring the distance accurately within less than one inch. A second highlight had occurred the previous year, when he detected ammonia in Sagittarius B2, near the center of the galaxy; Townes's discovery demonstrated that interstellar gas exists at much higher densities than had been thought. When radio astronomers, excited by Townes's discovery, turned their antennas toward the constellation of Orion, they found traces of water at such intensities that there was only one explanation: natural masers must occur on an astronomical scale. As Townes boasted, "A single astrophysical water maser can put out much more power than the total radiation from the sun, all at a single … frequency." Since then a number of such masers have been found, lending strong experimental support for the existence of black holes. After 1982 Townes shifted his focus to the infrared spatial interferometer, a device that uses a complex system of mirrors and lasers to measure the size of stars and to discover clouds of dust and gas that are invisible to normal telescopes.

Throughout his career Townes has displayed a special talent for administration. On leave from Columbia between 1959 and 1961, he served as vice president and director of research at the Institute for Defense Analysis, and he established "Jason," a regular gathering of academic scientists and industry representatives whose purpose was to make recommendations to Washington on important scientific topics, such as the development of nuclear energy, control of thermal pollution, and chemical and biological warfare. In 1966 he was appointed to the President's Scientific Advisory Committee (a position he continues to hold) and later served as chair of both the Strategic Weapons Panel of the Defense Department and the Science and Technology Advisory Committee for Manned Space Flight of the National Aeronautics and Space Administration; in this last capacity he made the initial suggestion for the Lunar Rover. He also served as president of the American Physical Society in 1967 and on the Technical Advisory Committee for General Motors.

In addition to the Nobel Prize and numerous honorary degrees, Townes has received medals from the American Academy of Arts and Sciences, the Franklin Institute, the Institute of Physics, and the National Academy of Sciences. In 1967 he received the Institute of Electrical and Electronic Engineers' Medal of Honor "for his significant contributions in the field of quantum electronics which have led to the maser and the laser." Townes has had a brilliant academic career as a professor, administrator, and researcher, but his name always will be associated with a single innovation: the technique of wave amplification through internal reflection, leading to the stimulated emission of radiation—the laser. In Life magazine's 1997 poll naming the most influential people of the last millennium, Townes was 819th on the list.

For additional information about the development of the laser, see Charles H. Townes, How the Laser Happened: Adventures of a Scientist (1999).

Hartley S. Spatt