20 Mars – Thesis defense - Diane Stoffel

09 h30 Institut Lasers and Plasmas - Le Barp

Nd:Lu:CaF2 laser cristal characterization for amplification at 1053 nm.

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 Phosphate glass doped with Neodymium material to work at 1053 nm with a repetition rate of 1 shot / 5 min 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 view of achieving a repetition rate of 10 Hz. In this PhD work, we report a characterization of the thermal induced effects under a diode inhomogeneous and transverse pump with an energy density of 13 J/cm2. We begin by studying the spatially resolved induced birefringence with a cross polarizer-analyzer setup. 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. A detailed study of the influence of the crystal orientation on the induced birefringence is presented to explain the disparity observed on the different samples Nd :Lu :CaF2 measurements.

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