Editing Light-emitting diode (section)

== Physics of light production and emission ==
{{main|Light-emitting diode physics}}
In a light-emitting diode, the recombination of electrons and electron holes in a semiconductor produces light (be it infrared, visible or UV), a process called "[[electroluminescence]]". The [[wavelength]] of the light depends on the energy [[band gap]] of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light.<ref name="pears1">{{cite book|last1=Pearsall|first1=Thomas|title=Photonics Essentials, 2nd edition|publisher=McGraw-Hill|date=2010|url=https://www.mheducation.com/highered/product/photonics-essentials-second-edition-pearsall/9780071629355.html|isbn=978-0-07-162935-5|access-date=February 25, 2021|archive-date=August 17, 2021|archive-url=https://web.archive.org/web/20210817005021/https://www.mheducation.com/highered/product/photonics-essentials-second-edition-pearsall/9780071629355.html|url-status=dead}}</ref>

Unlike a [[laser]], the light emitted from an LED is neither spectrally [[Coherence (physics)|coherent]] nor even highly [[monochromatic]]. Its [[Spectrum#Electromagnetic spectrum|spectrum]] is sufficiently narrow that it appears to the [[color vision|human eye]] as a pure ([[Colorfulness#Saturation|saturated]]) color.<ref>{{Cite web|title=LED Basics {{!}} Department of Energy|url=https://www.energy.gov/eere/ssl/led-basics|access-date=2018-10-22|website=www.energy.gov}}</ref><ref>{{cite web|author=<!--Staff writer(s); no by-line.-->|date=2013-07-25|title=LED Spectral Distribution|url=https://optiwave.com/resources/applications-resources/optical-system-led-spectral-distribution/|access-date=20 June 2017|website=optiwave.com}}</ref> Also unlike most lasers, its radiation is not [[Coherence (physics)#Spatial coherence|spatially coherent]], so it cannot approach the very high [[Radiance|intensity]] characteristic of [[laser]]s.