TGG Faraday Crystals / Terbium Gallium Garnet For Optical Isolator Devices

Terbium Gallium Garnet (TGG) Faraday Crystals

Terbium Gallium Garnet (TGG) is a crystal material for optical isolator devices. Optical isolator devices make use of the non-reciprocal Faraday effect in TGG. The Faraday effect is the rotation of the plane of polarization of a light beam as it is transmitted through a material in the presence of an external magnetic field coaxial with the light. The polarization rotation is in the same sense regardless of the direction of propagation of the light. An optical isolator is a Faraday rotator combined with suitably aligned polarizers which allows light to pass in one direction only.

Advantages Of TGG Include:

Superior to terbium-doped glasses

TGG has twice the Verdet constant of a Terbium-doped glass.

The thermal conductivity of crystalline TGG is an order of magnitude greater than a typical glass.

Optical losses are lower for TGG than Tb-doped glasses.

The combination of the above factors make TGG better suited to high average power applications.The principal limiting factor is thermally induced beam distortion. Beam distortion is less for TGG than Tb-doped glasses under the same power loading level