Terbium gallium garnet (TGG)

Terbium gallium garnet crystal (Tb3Ga5O12, TGG) has large magneto-optical constant, low light loss, high thermal conductivity and high laser damage threshold, and is widely used in YAG, Ti-doped sapphire and other multistage amplification, ring, seed injection lasers. TGG single crystal is the best magneto-optical material for making Faraday polarifiers and isolators, suitable for wavelengths of 400~1100nm(not including 470~500nm).

The Faraday polarimeter consists of a TGG crystal rod and a specially designed magnet. The polarization direction of the beam passing through the magneto-optical material will be deflected under the action of the magnetic field, and the deflection direction is only related to the magnetic field direction, and has nothing to do with the beam propagation direction. The optical isolator consists of a 45° deflected polarimeter and a pair of suitably placed polarizers, which allow the beam to pass in only one direction, while blocking the backpropagation beam.