Thin-Film Evaporative Cooling of a Side-Pumped Solid-State Laser Diode Oscillator for Space-Based LIDAR Applications

摘要

A concept for cooling side-pumped laser crystals, using a thin film of evaporating fluid, was investigated for use on future space-based light detection and ranging (LIDAR) instruments. Analyses of the solid crystal domain show that the thin-film cooling scheme will result in improved thermal management of the lanthanide crystal material investigated. Several candidate flow configurations are presented to produce the desired fluid flow across the crystal surface. One-dimensional, axial flow, two-fluid evaporation models were then solved to characterize the fluid and thermal performance of two of the proposed flow configurations. In addition, an incipience model is presented to determine the film thickness constraints necessary to suppress nucleate boiling. The bulk flow model indicates that excellent thermal management of the crystal, low liquid velocities, and low liquid pressure drops are possible with the two axial flow configurations analyzed. The incipience model indicates that liquid film thickness less than 10 microns may be necessary to ensure the complete absence of vapor bubbles in the liquid flowfield. This result indicates a need to develop three-dimensional fluid models for future studies so that more complex flow geometries may be studied.