Thermooptically perturbed resonators

Heating of intracavity solid-state materials causes isotropic and anisotropic variations in the index of refraction which lead to optical phase and amplitude distortions of the oscillating mode. Two important perturbations are discussed: stress birefringence in optically pumped laser rods and spherical aberration due to heating of intracavity elements, such as a nonlinear crystal, by the laser beam. While these perturbations are well determined, their effect on optical resonators cannot be inferred from the single-pass data in any simple way.