LASERS: Variety

LASERS: Variety

(Wikipedia excerpt: ..."...A laser [L] is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word [L] originated as an acronym for light amplification by stimulated emission of radiation.[1][2] The first [L] was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow and the optical amplifier patented by Gordon Gould.[3][4][5]

A [L] differs from other sources of light in that it emits light that is coherent. Spatial coherence allows a [L] to be focused to a tight spot, enabling uses such as optical communication,[6] [L] cutting, and lithography. It also allows a [L] beam to stay narrow over great distances (collimation), used in [L] pointers, lidar, and free-space optical communication. [L] can also have high temporal coherence, which permits them to emit light with a very narrow frequency spectrum. Temporal coherence can also be used to produce ultrashort pulses of light with a broad spectrum but durations as short as an attosecond....")