Nanosecond laser damage initiation at 0.35  μm in fused silica

In nanosecond regime, the laser-induced damage density at the exit surface of fused silica optics at the wavelength of 0.35 μm shows a characteristic behavior: in a specific fluence range, the surface damage density begins to grow exponentially as a function of fluence and then tends to saturate at high fluences. Up to now, no satisfactory explanation of these peculiarities could be provided. We herein detail a statistical model based on laser-matter interaction, where two types of absorbing precursors are involved in the energy deposit: subsurface micro-cracks and surface impurities. We show that the reported model predicts this characteristic damage density for a large range of fluences and different polishing processes.