<title>Normal and interfacial stresses in thin film coated optics: the case of diamond-coated zinc sulfide windows</title>

Abstract

Optical components such as mirrors or windows consisting of a substrate and a coating made up of thin films created at elevated temperatures exhibit substantial residual stresses induced by growth strains as well as thermoelastic strains that develop during the cool-down phase. A comprehensive description of these stresses must include not only the normal stresses in the film layers and the substrate but also the interfacial shearing stresses, which may cause delamination to occur. The primary purpose of this paper is to take advantage of recent progress in describing elastic interactions in multilayered laminates for obtaining conceptually correct formulas for the residual stresses and the substrate's curvature of thin-film coated optics. Available analytical solutions for the normal stresses of elastically isotropic structures made no assumptions regarding layer thicknesses but disregard the potential impact of edge effects.