Nonlinear processes and laser damage induced by a temporally modulated nanosecond UV laser beam. Part II: Kerr self-focusing

In this paper, we study the impact of Kerr self-focusing on laser-induced damage of fused silica with temporal modulation. In our experiments, temporal modulations are generated with high bandwidth amplitude modulators between 2 and 10 GHz. Measurement of the spatial profile after propagation is made possible due to a dedicated imaging setup. First results without temporal modulation experimentally and numerically show that the nonlinear gain increases exponentially with intensity. Complementary experiments with temporal modulation at different frequencies show an increase in the nonlinear gain. Eventually, we show that laser-induced damage is enhanced with amplitude modulation, with a dependence on the frequency of the amplitude modulation. Optimization of phase modulation allowed us to mitigate backwards stimulated Brillouin scattering and to focus on the sole impact of Kerr self-focusing on laser-induced damage.(c) 2023 Optica Publishing Group