Editing Faraday rotator (section)

{{Short description|Optical polarization rotator based on the Faraday effect}}
[[Image:Faraday-effect.svg|thumb|right|250px|Polarization mechanism due to the Faraday effect. The field lines are usually closed through a [[permanent magnet]] around the rotator.]]
A '''Faraday rotator''' is a [[polarization rotator]] based on the [[Faraday effect]], a [[magneto-optic effect]] involving transmission of light through a material when a longitudinal static magnetic field is present. The [[polarization (waves)|state of polarization]] (such as the axis of [[linear polarization]] or the orientation of [[elliptical polarization]]) is rotated as the wave traverses the device, which is explained by a slight difference in the [[phase velocity]] between the left and right [[circular polarization]]s. Thus it is an example of [[circular birefringence]], as is [[optical activity]], but involves a material only having this property in the presence of a [[magnetic field]].