Editing Kerr effect (section)

{{Short description|Change in refractive index of a material in response to an applied electric field}}
{{About|the Kerr nonlinear optical effect|the magneto-optic phenomenon of the same name|magneto-optic Kerr effect}}
{{Use American English|date = March 2019}}
The '''Kerr effect''', also called the '''quadratic electro-optic''' ('''QEO''') '''effect''', is a change in the [[refractive index]] of a material in response to an applied [[electric field]]. The Kerr effect is distinct from the [[Pockels effect]] in that the induced index change for the Kerr effect is [[directly proportional]] to the ''square'' of the electric field instead of varying linearly with it. All materials show a Kerr effect, but certain liquids display it more strongly than others. The Kerr effect was discovered in 1875 by Scottish physicist [[John Kerr (physicist)|John Kerr]].<ref>{{cite journal | last= Weinberger |first=P. | title = John Kerr and his Effects Found in 1877 and 1878 | journal = Philosophical Magazine Letters | volume = 88 | issue = 12 | pages = 897–907 | url = http://www.pwein.at/physics/Lectures/Famous-Papers/PML-2008.pdf | doi = 10.1080/09500830802526604 | date = 2008|bibcode = 2008PMagL..88..897W |s2cid=119771088 }}</ref><ref>{{cite journal | first= John |last=Kerr | title = A new relation between electricity and light: Dielectrified media birefringent | journal = Philosophical Magazine |series= 4  | volume = 50 | issue = 332 | pages = 337–348 |date = 1875 |doi=10.1080/14786447508641302 }}</ref><ref>{{cite journal | first= John |last=Kerr | title = A new relation between electricity and light: Dielectrified media birefringent (Second paper) | journal = Philosophical Magazine |series=4  | volume = 50 | issue = 333 | pages = 446–458 |date = 1875 |doi=10.1080/14786447508641319 }}</ref>

Two special cases of the Kerr effect are normally considered, these being the Kerr electro-optic effect, or DC Kerr effect, and the optical Kerr effect, or AC Kerr effect.