Influence of laser polarization on the laser-induced damage threshold: Comparison with photoionization theory

The influence of laser polarization on the laser-induced damage threshold of fused silica is presented. Measurements were performed using femtosecond and nanosecond laser pulse durations. The impact of laser polarization on the laser damage varies with laser wavelength. While no difference in UV laser damage was observed between linear and circular polarizations, circular polarization improved the damage resistance of fused silica to infrared and visible laser radiation in comparison with linear polarization. By measuring the femtosecond laser damage of a SiO2 thin film deposited onto a substrate, we show that the ratio between the bandgap of the sample and the photon energy causes the polarization dependent laser damage to change. These experimental findings are explained by considering the photoionization theory for solids.