The magneto-optic effect occurs when a magnetic field breaks the time-reversal symmetry of a medium, causing left- and right-circularly polarized light to experience different refractive indices. This results in the rotation of the plane of polarization for linearly polarized light passing through the material. Engineers exploit this non-reciprocal behavior to build optical isolators, which allow light to pass in one direction but block back-reflections.
The isolator relies on the magneto-optic effect in a Faraday rotator crystal to keep the back-reflections from destabilizing the seed laser.
Related terms
Optical isolator
A one-way valve for light that passes a beam forward and blocks reflections from returning to the laser.
Voigt effect
The induced birefringence in a medium subjected to a transverse magnetic field.
magneto-optic Kerr effect
The change in polarization and intensity of light reflected from a magnetized surface.