Numerical Study of a Thermally-compensated High-energy Double-pass Nd:YAG Amplifier Design

We conducted a comparative study of double-pass Nd:YAG laser amplifiers by comparing the thermally-induced optical losses of various designs through numerical simulations. The simulation code was developed to estimate the total optical losses from three thermal effects: depolarization, thermal lensing, and bi-focusing. At first, we verified the code with the well-known single-rod amplifier configurations. After that, we extended the code for dual-rod designs, which are more appropriate for high-energy applications. Finally, the adoption of a diverging input beam is suggested to reduce thermal losses dramatically and to avoid stubborn design issues, such as damage, aberration, system complexity, etc., in dual-rod high-energy double-pass amplifiers.