Temperature dependence of optical anisotropy parameter of CaF2, BaF2 and SrF2 materials

Thermally induced depolarization in undoped CaF2, BaF2 and SrF2 crystals was measured. The obtained results were used to determine temperature dependence of the optical anisotropy parameter ξ of these materials in the 80-300 K range. Temperature dependence of the orientation of crystallographic axes corresponding to the “zero depolarization” orientation was found. It was revealed that thermally induced depolarization in the studied materials cooled to 80 K reduces by more than 100 times, with changes in the parameter ξ being 5.8%, 6.4% and 28%, respectively.