Numerical Analysis of Thermal Effects in a Concept of a Cryogenically Cooled Yb: YAG Multislab 10 J/100-Hz Laser Amplifier

Abstract

A thermo-optical design study of different slab geometries for a cryogenically cooled multislab amplifier operating at 10 J/ 100 Hz is presented. A finite element method (FEM) is used for 3-D analysis of heat distribution, temperature, stress and strain. From this data, birefringence, depolarization losses and wavefront distortion are calculated for a single pass through the amplifier consisting of four slabs. A comparison of different slab shapes shows that a square-shape geometry produces the smallest thermal gradients at the outer sides of the beam region, which results in smaller depolarization losses. Although the design with square-shape slabs is more sensitive to misalignment, our study shows better results compared to the case of circular-shape slabs.

Numerical Simulation of Thermo-Optic Effects in an Nd: Glass Slab with Low Thermally Induced Wavefront Distortion

“…There are some reports about theoretical calculations of thermo-optic effects in the Yb: YAG gain medium with a cladding layer [23,24], but the sizes of pump area in the literature are the same as the Yb: YAG gain medium, which are in ideal cases and require the extremely high performance of the beam alignment. Beam misalignment would cause high-order wavefront distortion, which is difficult to compensate [25]. Actually, the size of the pump area is usually smaller than the gain medium when considering the coupling efficiency and experimental operation difficulty.…”