Editing Laser diode (section)

{{Short description|Semiconductor laser}}
{{Infobox electronic component
| name = Laser diode
| image = Diode laser.jpg
| caption = A packaged laser diode shown with a [[penny]] for scale: a 488&nbsp;nm [[InGaN]] green-blue laser, which became widely available in mid-2018.
| type = [[semiconductor]], [[light-emitting diode]]
| working_principle = [[semiconductor]], [[carrier generation and recombination]]
| invented = [[Robert N. Hall]], 1962; [[Nick Holonyak|Nick Holonyak, Jr.]], 1962
| first_produced = 
| pins = [[Anode]] and [[cathode]]
| symbol = 
| symbol_caption = 
}}
[[file:Laser diode chip.jpg|thumb|The laser diode chip removed and placed on the eye of a needle for scale]]
[[File:Laser diode with the case and window removed-powered off.jpg|thumb|A laser diode with the case cut away. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power.]]
[[File:Laser diode with case cut away.jpg|thumb|SEM ([[scanning electron microscope]]) image of a commercial laser diode with its case and window cut away. The anode connection on the right has been accidentally broken by the case cut process.]]

A '''laser diode''' ('''LD''', also '''injection laser diode''' or '''ILD''' or '''semiconductor laser''' or '''diode laser''') is a [[semiconductor]] device similar to a [[light-emitting diode]] in which a diode pumped directly with electrical current can create [[active laser medium|lasing]] conditions at the diode's [[p–n junction|junction]].<ref name="ColdrenCorzine2012">{{cite book|author1=Larry A. Coldren|author2=Scott W. Corzine|author3=Milan L. Mashanovitch|title=Diode Lasers and Photonic Integrated Circuits|url=https://books.google.com/books?id=D6Ub126rtPoC|date=2 March 2012|publisher=John Wiley & Sons|isbn=978-1-118-14817-4}}</ref>{{rp|3}}

Driven by voltage, the doped p–n-transition allows for [[carrier generation and recombination|recombination]] of an electron with a [[electron hole|hole]]. Due to the drop of the electron from a higher energy level to a lower one, radiation is generated in the form of an emitted photon. This is spontaneous emission. Stimulated emission can be produced when the process is continued and further generates light with the same phase, coherence, and wavelength.

The choice of the semiconductor material determines the wavelength of the emitted beam, which in today's laser diodes range from the [[infrared]] (IR) to the [[ultraviolet]] (UV) spectra. Laser diodes are the most common type of lasers produced, with a wide range of uses that include [[fiber-optic communication]]s, [[barcode reader]]s, [[laser pointer]]s, [[CD]]/[[DVD]]/[[Blu-ray]] disc reading/recording, [[laser printing]], [[laser scanning]], and [[light beam]] illumination. With the use of a phosphor like that found on white [[LED]]s, laser diodes can be used for general illumination.