PNNL

Abstract

When a transparent, wide bandgap insulator is exposed to sub-bandgap laser irradiation, defects at and near the surface often dominate the response in terms of particle emission and eventual ablation of material. We explored the consequences of applying a variety of stimuli that can generate defects on single crystal surfaces of inorganic ionic crystals. The stimuli include: electron beam irradiation, a second laser beam, mechanical treatment, and thermal treatment. We found that a common theme evolves where these stimuli generate sites for strong interactions of the probing laser beam, leading to a dramatic decrease in the laser intensities needed for ejection of ions, neutrals, and eventual plume formation.