Eyesafe laser diode arrays for resonant pumping of Er-doped gain media optimized for cryogenically cooled operation

Growing interest in high-power lasers in the eye-safe spectral domain has instigated the development of solid-state lasers based on Er(3+)-doped materials. Impressive results have been demonstrated in resonantly pumped lasers based on Er:YAG crystals, and cryogenic cooling of the laser crystal has been shown to improve the laser performance. In these initial demonstrations, the pump lasers were InGaAsP/InP 1530 nm laser diode arrays operating at room temperature. The development of pump lasers specifically optimized for operation at cryogenic temperatures along with the solid-state laser crystal will provide disruptive benefits for the complete laser system, including increased pump power, improved laser efficiency, and a compact optical system architecture. Based on work completed during our Phase I effort, we will achieve further improvements in cryogenic pump operation based on an integrated approach for improving various design elements such as epitaxial structure, spectral stabilization, mechanical mounting techniques, and beam collimation. The goal of the program is to deliver a high brightness pump source with an output power of >500 W and a wall plug efficiency of >75%.