Enhancement of laser-induced damage threshold of optical coatings by ion-beam etching in vacuum environment

Abstract

Ion-beam sputtering (IBS) method was used to etch the different thickness of the outer layer overcoat for high reflection film. Laser resistance improvements enabling to exceed 1.5× have been observed on high reflection coatings. The smoothing process of surface and subsurface convex defect induced by ion-beam etching caused the decreasing electric field intensity. A process model was presented to understand the smoothing process of surface and subsurface convex defect. The decreasing electric field intensity, accompanying with small surface roughness value, low defect density and organic contamination adsorption concentration of sample surface, was attributed to the high laser-induced damage threshold in vacuum environment.