Recent Development of High-Energy Short-Pulse Lasers with Cryogenically Cooled Yb:YAG

Abstract

High-power solid-state lasers are among the hot research directions at the forefront of laser research and have major applications in industrial processing, laser-confined nuclear fusion, and high-energy particle sources. In this paper, the properties of Yb:YAG and Nd:YAG crystals as gain media for high-power solid-state lasers were briefly compared, according to the results of which Yb:YAG crystals are more suitable for high-power applications. Then, the effects of the thermodynamic and spectral properties of Yb:YAG crystals with temperature were analyzed in detail, and it was shown that the laser beams amplified by the cryogenically cooled Yb:YAG crystals could have higher beam quality, higher pump absorption efficiency, lower pump threshold, and higher gain. The change in properties of Yb:YAG crystal at low temperature makes it more suitable as a gain medium for high-power lasers. Subsequently, two types of kilowatt-class lasers using cryogenically cooled Yb:YAG crystals as gain media are introduced—100 J, 10 Hz nanosecond lasers and 1 J, 1 kHz picosecond lasers. Their configuration, main parameters, and typical output results were analyzed. Finally, future directions in the development of cryogenically cooled Yb:YAG lasers are discussed.

Enhanced Yb:YAG Active Mirrors for High Power Laser Amplifiers

“…According to the available experimental data for Yb:YAG elements, in the temperature range of 80-300 K emission cross-section at the radiation wavelength (1030 nm) changes by a factor of ~10, the absorption cross-section at the pump wavelength changes by ~2 times, and the thermal conductivity changes by a factor of 5-10 times [39] depending on the degree of doping, the heat capacity is ~5 times [39]. Such changes in the parameters upon transition from cryogenic to room temperature make it necessary to take into account the active element temperature dependencies of the thermophysical and laser parameters.…”