Faraday Rotator
Faraday rotator is based on the nonreciprocity of magneto-optical materials, that is, it can rotate the polarization planes of the normal incident light and the reverse incident light of the same wavelength to the same direction and the same angle, independent of the beam propagation direction. If a Faraday rotator with 45 degree rotation of the polarization plane of the incident beam is placed between a pair of polarizers orthogonal to each other to form an optical isolator, it only allows the forward propagating beam to pass through the system and blocks the backward propagating beam.
Faraday rotator is an important component of optical isolator, which is widely used in various laser systems, such as multi-stage laser amplifier, optical parametric oscillator, ring laser, erbium-doped fiber amplifier, seed injection laser, optical switch, optical modulator and so on.