Abstract

High repetition-rate thermal loading of nonlinear crystals limits the conversion of efficiency of second harmonic generation (SHG). This paper presents a fully coupled thermal and optical description of SHG in an anisotropic, thermally absorbing medium which may be either uniaxial or biaxial. Computations of beam energies and wavefront structure are performed numerically. The program propagates a fundamental and second harmonic beam through the crystal and then recalculates the changed thermal gradients and indices of refraction before propagation of the following pulse. It is assumed that the optical and thermal properties of the medium are static during the propagation of any single pulse. Typical pulses have half-power widths of 10 to 20 ns, carry 1 Joule of energy, have Gaussian temporal and spatial profiles and are repeated at 20 to 30'Hz. Following each pulse the deposited heat is allowed a three-dimensional diffusion in the crystal according to the time-dependent heat equation.

© 1985 Optical Society of America