KDP crystal orientation influence on the nanosecond laser-induced damage at 1064nm

We investigate the influence of THG-cut KDP crystal orientation on laser damage at 1064 nm under nanosecond pulses. This study makes a connection between precursor defects and the influence of their orientation on the laser damage. Previous investigations have already been carried out in various crystals and particularly for KDP, indicating propagation direction and polarization dependences. We performed experiments for two orthogonal positions of the crystal and results clearly indicate that KDP crystal laser damage depends on its orientation. We carried out further investigations on the effect of the polarization orientation, by rotating the crystal around the propagation axis. We then obtained the evolution of the damage probability as a function of the rotation angle. To account for these experimental results, we propose a model based on heat transfer, the Mie theory and a Drude model. The geometry of the precursor defects is assumed to be ellipsoid-shaped and we numerically introduce absorption efficiency calculations for this geometry. Modeling simulations are in good agreement with experimental results.