This results in the "magneto-optic effect".

In response to a magnetic field, some materials can have a dielectric tensor that is complex-Hermitian; this is called a gyro-magnetic or magneto-optic effect.

Some modulators utilize an acousto-optic effect or magneto-optic effect or take advantage of polarization changes in liquid crystals.

The Allison magneto-optic effect, or simply the Allison effect, was discussed by Irving Langmuir in his now famous 1953 lecture on pathological science.

"Named for the magneto-optic effect in which the polarization plane of an electromagnetic wave is rotated under the influence of a magnetic field parallel to the direction of propagation."

A 'Faraday rotator' is an optical device that rotates the polarization of light due to the Faraday effect, which in turn is based on a magneto-optic effect.

(Despite this, it is still useful to consider the time-reversal non-invariance in a local sense when the external field is held fixed, as when the magneto-optic effect is analyzed.

The operation of the device depends on the Faraday effect (which in turn is produced by magneto-optic effect), which is used in the main component, the Faraday rotator.

A magneto-optic effect is any one of a number of phenomena in which an electromagnetic wave propagates through a medium that has been altered by the presence of a quasistatic magnetic field.

An optical switch may operate by mechanical means, such as physically shifting an optical fiber to drive one or more alternative fibers, or by electro-optic effects, magneto-optic effects, or other methods.

In physics the magneto-optic Kerr effect (MOKE) or the surface magneto-optic Kerr effect (SMOKE) is one of the magneto-optic effects.

Refractive modulators most often make use of electro-optic effect (amplitude & phase modulation), other modulators are made with acousto-optic effect, magneto-optic effect such as Faraday and Cotton-Mouton effects.

Quadratic Magnetic Rotation (also known as QMR or QMR effect) is a type of magneto-optic effect, discovered in the mid 1980s by a team of Ukrainian physicists.

He then worked for a year at the California Institute of Technology before becoming Tait Professor of Natural Philosophy at the University of Edinburgh in 1924, working on quantum optics and magneto-optic effects.

Fast optical switches, such as those using electro-optic or magneto-optic effects, may be used to perform logic operations; also included in this category are semiconductor optical amplifiers, which are optoelectronic devices that can be used as optical switches and be integrated with discrete or integrated microelectronic circuits.

In general, magneto-optic effects break time reversal symmetry locally (i.e. when only the propagation of light, and not the source of the magnetic field, is considered) as well as Lorentz reciprocity, which is a necessary condition to construct devices such as optical isolators (through which light passes in one direction but not the other).