Laser

A laser produces a narrow, intense beam of coherent light through stimulated emission of radiation. Its output can be concentrated in space, time, and wavelength.

Stimulated emission: An excited atom or molecule emits a photon when triggered by another photon, producing a matching photon. This process creates copies of photons that amplify the laser field.
Photon: The quantum of electromagnetic radiation, carrying energy and momentum. Stimulated emission adds photons with the same frequency and direction as the triggering photon.
Laser cutting: A manufacturing process that uses a focused laser beam to cut or engrave material. Concentrated optical power removes material along precise paths.
Light-emitting diode: A semiconductor device that emits light when electrical current crosses a junction. LEDs are efficient light sources but generally lack the narrow beam and coherence of lasers.
Albert Einstein: A German-born theoretical physicist whose work reshaped modern physics, including the theory of stimulated emission. His 1917 treatment of radiation introduced the process underlying laser amplification.
Population inversion: A state in which more particles occupy an excited energy level than a lower one. It lets stimulated emission exceed absorption in the laser medium.
Electromagnetic spectrum: The full range of electromagnetic radiation, arranged by frequency or wavelength. A laser occupies a selected region of this spectrum, from infrared to ultraviolet and beyond.
Optical fiber communication: The transmission of information as light pulses through optical fibers. Lasers provide compact, rapidly modulated sources for fiber-optic data links.
Thermal radiation: Electromagnetic radiation emitted by matter because of its temperature. Thermal sources emit broad, incoherent light rather than a tightly selected laser beam.
Charles H. Townes: An American physicist who helped develop the maser and later advanced the concept of the optical laser. His maser work demonstrated stimulated-emission amplification before optical lasers were built.

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