Damage to multilayer dielectric coatings by nanosecond laser pulses

A study was made of damage to multilayer electron-beam-evaporated coatings made from zirconium and silicon dioxides by radiation of wavelengths 1.06 and 0.53 μ and pulse duration 1 nsec from a single-mode neodymium laser. The damage thresholds for the strongest coatings, which were highly reflecting for the first two harmonics of the neodymium laser, were nearly equal at the two wavelengths. Investigations were made of the morphological characteristics of damage to the coatings and of the role of absorbing inhomogeneities in the appearance of microscopic damage, and their influence on the size dependence of the damage threshold was demonstrated. A comparison was made between the optical strengths of different dielectric coatings and of a K8 glass surface.