Editing Optical amplifier (section)

{{Short description|Device that amplifies an optical signal}}
{{distinguish|Operational amplifier}}
{{Use American English|date = April 2019}}
[[File:A Guiding Star.jpg|thumb|300px|Optical amplifiers are used to create [[laser guide star]]s which provide feedback to the [[adaptive optics]] control systems which dynamically adjust the shape of the mirrors in the largest astronomical [[telescope]]s.<ref>{{cite web|title=A Guiding Star|url=http://www.eso.org/public/images/potw1443a/|website=Eso.org|publisher=European Southern Observatory|access-date=29 October 2014}}</ref>]]

An '''optical amplifier''' is a device that amplifies an [[optical]] [[signal (information theory)|signal]] directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a [[laser]] without an [[optical cavity]], or one in which [[feedback]] from the cavity is suppressed. Optical amplifiers are important in [[optical communication]] and [[laser physics]]. They are used as [[optical repeater]]s in the long distance [[fiber-optic cable]]s which carry much of the world's telecommunication links.

There are several different physical mechanisms that can be used to amplify a light signal, which correspond to the major types of optical amplifiers. In doped fiber amplifiers and bulk lasers, [[stimulated emission]] in the amplifier's [[gain medium]] causes amplification of incoming light. In semiconductor optical amplifiers (SOAs), [[electron]]–[[electron hole|hole]] [[Carrier generation and recombination|recombination]] occurs. In [[Raman amplifier]]s, [[Raman scattering]] of incoming light with [[phonon]]s in the lattice of the gain medium produces [[photon]]s coherent with the incoming photons. [[Parametric amplifier]]s use parametric amplification.