Laser facility such as the Megajoule Laser dedicated to laser-matter interaction including inertial fusion need pre-amplifier modules (PAM) which must respect a high beam quality. The current PAM use Nd:Phosphate material to work at 1053 nm with a repetition rate of 1shot/5min limited by a low thermal diffusion. However, it would be interesting to increase the shot rate for alignment or diagnostic purposes. Therefore, we propose to change this amplification material by crystal Nd:Lu:CaF2 with a thermal diffusion ten times higher in a new amplification architecture scheme in view of achieving a repetition rate of 10Hz. However, this material must fulfill the beam specifications to be integrated in the actual amplification chain. We report here a characterization of the thermal induced effects under a diode pump energy density of 13J/cm2. We begin by studying the spatially resolved induced birefringence with a cross polarizer-analyzer setup and then we measure the wave-front variations along two perpendicular polarizations. As the thermal elevation implies stress and then birefringence, we use an IR camera to study the surface thermal diffusion of the samples. Finally we reconstruct the stress pattern of our samples by simulating the global setup with COMSOL software which includes the thermal and mechanic Multiphysics interaction. This model allows us first to compare with experimental results and then to entirely simulate the mechanical behavior of this new material. These results obtained for the regenerative amplifier would enable us to study a new architecture scheme like disks multi-pass amplifier.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon