Laser Induced Surface Damage

Abstract

A summary of recent investigations of surface damage of transparent dielectrics is presented. Damage threshold measurements made on Owens-Illinois ED-2 laser glass at normal incidence and at Brewster's angle are reported. For 30-nsec pulses at normal incidence, exit surface damage thresholds are typically 100 J/cm(2) for ED-2 glass. The observed ratio between entrance and exit damage thresholds for the two geometries can be explained by considering the electric field strengths at the surfaces and including interference between incident and reflected light waves. A similar analysis is applied to surface damage that occurs during total internal reflection. Finally the morphology of surface damage of ED-2 laser glass is described, and a model based upon reflections from the laser induced plasma is proposed to explain the observations.