Charles H. Townes

Charles H. Townes (1915–2015) was an American physicist who shared the 1964 Nobel Prize in Physics for work that led to the maser and laser.

Maser: A device that amplifies or generates coherent electromagnetic waves through stimulated emission, usually at microwave frequencies. Townes and colleagues built the first working maser in 1953.
Microwave spectroscopy: The study of molecular energy levels by measuring absorption or emission of microwave radiation. Townes used it to investigate molecular transitions that could power a maser.
Arthur L. Schawlow: An American physicist who shared the 1981 Nobel Prize in Physics for work on laser spectroscopy. Schawlow and Townes published a 1958 proposal for extending maser principles to optical frequencies.
Columbia University: A private research university in New York City, founded in 1754. Townes developed the ammonia maser at Columbia’s physics department.
Laser spectroscopy: The use of laser light to measure atomic or molecular properties with high precision. Townes’s laser proposals opened a route to precise optical spectroscopy.
Laser: A device that produces coherent light through stimulated emission of radiation. Townes’s maser research helped establish the principles used to create lasers.
Population inversion: A condition in which more particles occupy an excited state than a lower energy state. A population inversion lets a maser amplify radiation rather than absorb it.
James P. Gordon: An American physicist who co-built the first ammonia maser with Charles Townes and Herbert Zeiger. Gordon carried out the experimental work that made Townes’s maser proposal a functioning device.
Bell Labs: A research and development organization known for major contributions to telecommunications and the physical sciences. Townes worked there during World War II on radar and microwave technology.
Molecular astronomy: The study of molecules in space through their electromagnetic spectra. Townes helped use spectral methods to reveal molecules in interstellar clouds.

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