Surface damage caused by laser radiation to solid transparent dielectrics

The dependence of the threshold power density of laser radiation on the diameter of a focal spot is calculated for the surface damage of solid transparent dielectrics. The calculation is carried out on the assumption that this dependence is governed by the development of thermal instabilities at absorbing inhomogeneities. The results obtained explain physically the experimental data, particularly the observed increase in the surface breakdown threshold when the surface of a dielectric is subjected to a preliminary treatment.