Study of a thermal lens in thin laser-ceramics discs

Thermal distortions of the radiation phase are studied theoretically in laser ceramics. Special attention is paid to the small-scale phase modulation inherent in ceramics, which is caused by the arbitrary orientation of its single-crystal grains. Expressions are derived which describe the average phase distortion and its dispersion in disc elements in approximations of a thin disc cooled through optical surfaces and of weak heat exchange. The numerical calculation has confirmed the high accuracy of these expressions. The proposed approximate solutions of the heat conduction and elasticity equations are of their own importance. In particular, the obtained solutions can be used to describe phase and polarisation distortions of radiation in an arbitrarily oriented single-crystal disc.