Charles H. Townes (1915–2015) Laser Co-Inventor, Astrophysicist and US Presidential Adviser

COMMENT OBITUARY Charles H. Townes (1915–2015) Laser co-inventor, astrophysicist and US presidential adviser.

harles Hard Townes trans- instrumentation for astronomy formed modern society by based on techniques drawn from the helping to invent the laser. field of quantum electronics. CHe also made crucial contributions A breakthrough during this to astrophysics and infrared astron- period was his discovery of water omy, and served as a US presidential and ammonia molecules in inter- science adviser. stellar clouds — accumulations of Townes, who died on 27 January gas, plasma and dust in the interstel- in Oakland, California, was born in lar medium. Astrophysicists knew Greenville, South Carolina, in 1915. that such clouds existed, but were He attended Furman University in surprised to learn that complex Greenville, and in 1935 received molecules, including those asso- undergraduate degrees in both phys- ciated with life, could exist in the ics and modern languages. interstellar medium. He pursued graduate studies at Townes also developed techniques COLLECTION/GETTY LIFE PICTURE ALFRED EISENSTAEDT/THE Duke University in Durham, North for infrared astronomy. Infrared Carolina, after being turned down light penetrates much farther than from the California Institute of Tech- visible light into cosmic dust clouds, nology (Caltech) in Pasadena. On which are intimately connected receiving a master’s degree in 1936, with the formation of stars. With he again applied to Caltech, and this his students, he probed the centre of time was accepted. He completed his our Galaxy, and obtained evidence PhD in 1939 under physicist William for the presence of a supermassive Smythe on the process of isolating certain a description of how to construct a version of black hole and measured its mass. He also isotopes of a chemical element from others. the maser using visible light — a laser. Two monitored the diameter of the red-giant star After graduating from Caltech, Townes years later, Theodore Maiman of Hughes Betelgeuse and made the remarkable discov- joined the technical staff of Bell Telephone Research Laboratories in Malibu, Califor- ery that the measured diameter decreased by Laboratories in Murray Hill, New Jersey, nia, designed a functioning laser using an 15% over a mere 15 years. where he worked on the development of optically excited ruby crystal. Townes was an adviser to US presidents radar methods as part of the Second World The influence of the laser has been Dwight D. Eisenhower, John F. Kennedy and War effort. In 1948, he joined the faculty extraordinary, with applications in telecom- Richard Nixon. Among other committees, of Columbia University in New York City. munications, medicine, law enforcement, he chaired the advisory panel for the first His wartime work on radar had given him the military, astronomy and in everyday human landing on the Moon. crucial knowledge in microwave methods, life — it is used in just about everything Townes firmly believed that religious faith and in 1951 — while sitting on a park bench from supermarket scanners to eye surgery. was not incompatible with scientific explora- in Washington DC — he conceived of the Townes shared the 1964 Nobel Prize in Phys- tion of the cosmos, and he was respectful of all maser (microwave amplification by stimu- ics for his work on the maser–laser principle. religions. He argued for the “convergence of lated emission of radiation). In 1961, he left Columbia to become science and religion” — in his view, although This technique produces and amplifies provost at the Massachusetts Institute of each used very different methods, science and microwave radiation by prompting atoms or Technology (MIT) in Cambridge, Massachu- religion were similarly motivated by a desire molecules to make transitions from a high- setts. He maintained a small but productive to understand the mysteries of existence. energy state to a low-energy state, emitting a research programme, which largely con- As my teacher, mentor, colleague and photon in the process. Energy is supplied to centrated on lasers. He and his colleagues friend, Professor Townes had an enormous the maser by an electric discharge or another made measurements of the extremely nar- impact on my life. He was a kind and gener- microwave field. Masers are notable for their row range of wavelengths associated with ous man, and gave much of himself as both high coherence — the emitted molecules laser light, known as the Schawlow–Townes a policy adviser and a teacher. ■ within the maser beam oscillate with the linewidth. (Its properties had previously same frequency and phase. The behaviour been described theoretically by the pair.) Robert Boyd is the Canada Excellence is a result of a chain reaction in which the Townes and his co-workers also began to Research Chair in Quantum Nonlinear emission from one molecule triggers that of explore nonlinear optics, discovering among Optics at the University of Ottawa, Canada, its neighbours. other things a type of light scattering called and professor of optics and of physics at the Townes and his group successfully stimulated Brillouin scattering. University of Rochester, New York, USA. demonstrated the maser in the laboratory in In 1967, Townes moved to the University Charles Townes was his PhD adviser at the 1954 using ammonia gas. In 1958, along with of California, Berkeley, where he spent University of California, Berkeley, from Arthur Schawlow, his brother-in-law and a the rest of his career. Here, he turned his 1971 to 1977. future Nobel prizewinner, Townes published attention to astrophysics, developing e-mail: [email protected]