Schawlow, Arthur L. Formerly, Department of Physics, Stanford University, Stanford, California. Nobelist.
Khurgin, Jacob B. Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland.
Last reviewed:March 2020
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- Process of stimulated emission
- Types of lasers
- Gas lasers
- Solid-state lasers
- Semiconductor (diode) lasers
- Tunable lasers
- Short-pulse lasers
- Nonlinear optical techniques for wavelength range expansion
- Related Primary Literature
- Additional Reading
A device that uses the principle of amplification of electromagnetic waves by stimulated emission of radiation, generating a coherent beam of light in the infrared, visible, or ultraviolet portions of the electromagnetic spectrum. The term "laser" is an acronym for "light amplification by stimulated emission of radiation," or a light amplifier. Light amplification is achieved in the so-called gain medium, which is a solid, liquid, or gaseous material that possesses suitable properties such that when the material is externally excited, the probability of stimulated radiation emission in it exceeds the probability of radiation absorption. The vast majority of laser devices (Fig. 1) are amplifiers made into oscillators by feeding appropriately phased output back into the light input. In practice, the unmodified word “laser” has come to mean a device that actually is an oscillator, while the modifier “amplifier” as in “laser amplifier” (technically redundant) or in “optical amplifier” is generally used when referring to the gain medium operating without feedback. See also: Amplifier; Light; Maser; Oscillator; Radiation
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