Laser-induced damage and nonlinear absorption of ultrashort laser pulses in the bulk of fused silica

Abstract

In the last decade, investigations in fs-laser damage mechanisms have proven that the interaction of ultra-short laser pulses with dielectric matter is driven by electronic processes. This fact leads to a deterministic damage behavior and a well defined dependency of the laser-induced damage threshold (LIDT) on the absorption gap of the dielectric optical material. These facts have been considered in detail for dielectric thin films. Additionally, numerous investigations in filamentation, supercontinuum generation (SCG) and optical breakdown in bulk material have been published. The phenomena are also traced back to the interaction of ultra-short laser pulses with dielectric material. In contrast to thin films, these effects are based on a large interaction length of the beam with the dielectria. Consequently, additional nonlinear effects can contribute to the damage process of bulk materials. In the presented work, nonlinear absorption and the LIDT of fused silica are investigated. The influence of the propagation distance of the laser beam in the solid was in the focus of interest for an experiment on a series of fused silica samples of identical material and different thickness. The results of this study show that nonlinear absorption and laser-induced damage strongly vary in dependence of the sample thickness. The variations in the damage threshold range over more than one order of magnitude.