15 January 2007 Numerical and experimental study of focal spot degragation induced by particles on surface optics
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Abstract
Correctly determining the lifetime of optical components is a major issue in the operation of high power laser facilities such as the Laser Megajoule developed by the Commissariat a l'Energie Atomique (CEA). Laser damage that occurs at the surface is a main cause of optical aging, and may lead to dramatic degradation of the focal spot. To estimate the effect of such defects, we measured and calculated the distortion of the focal spot induced by "model defects." These "model defects" are circular silica dots randomly distributed on a silica substrate. The experiments were conducted in the ANTALIA facility at the Centre d'Etude Scientifique et Technique d'Aquitaine (CESTA). We performed numerical calculations of beam propagation with the Miro software, developed by the CEA. We obtain a remarkable correlation between measurements and simulations in the central part of the focal spot for large defects. However, experimental noise and measurement dynamics become serious problems when we confine our attention to smallerdefects (<500 micron) or to the diffuse light around the central part of the focal spot. We present some modifications of the ANTALIA experimental setup designed to overcome these problems.
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B. Martinez, V. Beau, S. Chico, S. Mainguy, J. L. Rullier, "Numerical and experimental study of focal spot degragation induced by particles on surface optics", Proc. SPIE 6403, Laser-Induced Damage in Optical Materials: 2006, 64030F (15 January 2007); doi: 10.1117/12.695455; https://doi.org/10.1117/12.695455
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