Articles techniques et présentations

High power lasers have a wide range of applications. The goal of this work is to analyze and further optimize a beam expander made of 2 lenses used with a kW class laser. The preliminary lens design is performed using an optical design software but its performance analysis, when used with a high power continuous wave laser, is simulated using COMSOL Multiphysics® and the Ray Optics Module. A comparative study is performed between a beam expander made of 2 Fused-Silica lenses and another one made of CaF2 and Fused-Silica lenses. The performance is evaluated by the mean of the transmitted wavefront error. Both a transient and a steady state analysis are evaluated. The steady state analysis is performed using the Bidirectionally coupled Ray Tracing study while a transient state analysis is performed coupling a Ray Tracing and a Time dependent study. The results of this analysis are given in terms of wavefront aberration level from which other quality metrics may be derived (wavefront Zernike decomposition, PSF,...) depending on the application system to be designed. Further improvement in the lens design (radius of curvatures, glass thickness,..) would then be possible with the Optimization Module in COMSOL®.