The dependence of optical anisotropy parameter on dopant concentration in Yb:CaF2 and Tb:CaF2 crystals

Optical anisotropy parameters of Yb3+:CaF2 with different concentrations of Yb3+ ions (2.6, 3, 4.2 at.% Yb3+) and 10 at.% Tb3+:CaF2 crystals were determined from measurements of thermally induced depolarization. It was shown that the optical anisotropy parameter depends on dopant, if its concentration is sufficiently high. The crystallographic axes orientation at which there is no thermally induced depolarization was found for each studied crystal.