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- Acronym for Light Amplification by Stimulated Emission of Radiation; a device that produces a powerful, highly directional, monochromatic, coherent beam of light. Laser consist of a transparent cylinder with a reflecting surface at one end and a partially reflecting surface at the other. Light waves are reflected back and forth, some of them emerging at the partially reflecting end. The light source may be a ruby, whose chromium atoms are excited by a flash lamp so that they emit pulses of highly coherent light, or a mixture of inert gases that produce a continuos beam, or a cube of treated gallium arsenide which emits infrared radiation when an electric current passes through it.
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| Abstract from DBPedia | A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond. Lasers are used in optical disc drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic and free-space optical communication, semiconducting chip manufacturing (photolithography), laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Semiconductor lasers in the blue to near-UV have also been used in place of light-emitting diodes (LEDs) to excite fluorescence as a white light source. This permits a much smaller emitting area due to the much greater radiance of a laser and avoids the droop suffered by LEDs; such devices are already used in some car headlamps.レーザー (英: laser) とは、Light Amplification by Stimulated Emission of Radiation（誘導放出による光増幅放射）の頭字語（アクロニム）であり、指向性と収束性に優れた、ほぼ単一波長の電磁波（コヒーレント光）を発生させる装置である。レーザとも表記される。レザーとも表記される場合もある。 レーザーの発明により、非線形光学という学問が生まれた。発生する電磁波は、可視光とは限らない。紫外線やX線などのより短い波長、また赤外線のようなより長い波長の光を出す装置もある。ミリ波より波長の長い電磁波を放射するものはメーザーと呼ぶ。 (Source: http://dbpedia.org/resource/Laser) |
