The use of crystalline quartz for compensation for thermally induced depolarisation in Faraday isolators

It is shown that a quartz crystal, which is placed inside a telescope and whose optic axis is parallel to a light beam, can reduce the depolarisation of radiation caused by thermally induced birefringence in a Faraday isolator. The isolation ratio was experimentally increased by a factor of eight. An important advantage of this method over previous methods is that standard commercial Faraday rotators can be used.