Thermal Distortions in Laser-diode– and Flash-lamp–pumped Nd:ylf Laser Rods

LLE Review, Volume 71 137 Laser-diode pumping of solid-state laser materials is proving to be much more advantageous over the more conventional technique of flash-lamp pumping. The electrical to optical efficiency of laser diodes is significantly higher than for flash lamps. In addition, the emission wavelength of laser diodes can be chosen to couple efficiently to the absorption band of the laser ion, resulting in very high overall laser efficiencies. Despite this level of efficiency, both laser-diode– and flashlamp–pumped systems deposit unwanted heat into the gain medium. The resultant thermal loading of the gain medium leads to thermal-optical wavefront distortions that can degrade the performance of a laser system. Exact eigenmode solutions of optical resonators with phase-aberrating elements can be numerically calculated using high-speed computers. These calculations require a detailed knowledge of the wavefront distortions induced by optical pumping in order to design compensating optics for the system. This is especially important when designing a high-average-power laser system.