TGG crystal Terbium Gallium Garnet is an essential magneto-optical crystal l for faraday polarizer. Faraday polarizer is composed of the TGG crystal rod and a specially designed magnet. The polarization of the beam through the magneto-optical materials deflexed and direction of the deflection only has some relations with the direction of the magnetic field and has nothing to do with the direction of the beam propagation. An optical isolator is an optical component which allows the transmission of polarized light in only one direction.