Optical isolators are passive, non-reciprocal devices that utilise the phenomenon of Magneto-Optic Rotation to isolate the source from reflections in an optical system. The heart of the optical isolator is based on a Faraday Rotator using, for example, Yttrium Iron Garnet-YIG (LPE and bulk) or Terbium Gallium Garnet-TGG single crystals.

These among other Faraday media have the ability, when in an appropriate magnetic field, to rotate the plane of linearly polarised light by an amount proportional to its length. YIG crystal is used for wavelengths from 1100 to 2100nm. TGG is utilised in several free space optical isolators for wavelengths between 500 and 1100nm.

All isolator units and Faraday rotators are supplied with a mounting collar for easy mounting and accurate alignment to the polarisation plane of a laser.