What is a laser?
Laser stands for "Light Amplification by Stimulated Emission of Radiation."
A laser is a device that creates and amplifies a narrow, intense beam of visible light. Making a laser beam involves getting a group of atoms to cooperate and release light in one direction at the same instant.
To make a laser, atoms or molecules of a gas, liquid or crystal, such as a ruby, are exited so that some are at higher energy levels. The resulting energy is bounced back and forth inside a cavity, so that the energy grows. It is then released in a sudden burst of "coherent radiation," according to scientists at Bell Labs, and all the atoms discharge in a rapid chain reaction.
The technology has roots that date back to the 1940s. But a paper titled Infrared and Optical Masers, published in 1958 by Arthur L. Schawlow and Charles H. Townes, is often cited as giving birth to lasers.
Maser stands for "Microwave Amplification by Stimulated Emission of Radiation." Microwave radiation is an invisible part of the overall electromagnetic spectrum.
Though Schawlow and Townes had not yet made an actual laser, they suggested in their paper that the principles of the maser could be extended to the optical regions of the light spectrum. They applied for and received a patent for the laser. Each researcher later received a Nobel Prize in physics for different aspects of their work (Townes in 1964 and Schawlow in 1981).
Theodore Maiman at Hughes Aircraft Company built the first working laser in 1960.
Besides pointing devices, lasers are used to cut metal, perform surgery and run bar-code scanners at the supermarket. Engineers use lasers to precisely measure distances, such as between multiple telescopes whose efforts are combined to create one large telescope. A future space-based telescope planned by NASA would use three spacecraft, flying in formation, coupled only by lasers.
Over the past decade, Townes has drawn on his experience with lasers to develop a novel technique for canceling out all but the most telling wavelengths of radiation coming from the stars. The method recently allowed him and some colleagues to make more precise measurements of stars, challenging conventional views of how some stars evolve.
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