Thermal stresses and end-bulging in the laser disc from a tetragonal [100]-cut crystal

The problem of thermal stresses and strains is considered in relation to the laser disc from a tetragonal crystal cut along [1 0 0] axis under plane stress approximation (for diode-pumped lasers). The formula describing the contribution of end-bulging of the disc to the optical power of the thermal lens is obtained. It is shown that end-bulging for anisotropic crystal is partially responsible for the astigmatism of the thermal lens. The relationship between the anisotropy of thermal expansion and the position of the principal meridional planes of the thermal lens is shown. Thermal stresses, strains and displacements, as well as the end-bulging term of the 'generalized' thermo-optic coefficient are calculated for a disc from an a-cut yttrium vanadate, Nd:YVO4. The stress fracture issues for this crystal are also analyzed.