Chalcogenide Glasses. Part 2. Optical Thickness - Temperature Relation in Chalcogenide Glass Films

摘要

The optical thickness, which is a multiplication of the refractive index and the physical thickness of a film, is the most important parameter in designing a spectral interference filter. This quantity should be stable against all environmental effects, particularly the heating effect. The changes in optical thickness due to heating may be divided into two categories; a reversible change and irreversible change. This report describes the reversible portion of changes in refractive index, film thickness and optical thickness with temperature, caused by temperature coefficient of refractive index and thermal expansion coefficient of chalcogenide glass films. Film compositions studied were; As2S3, As3S7, AsS4, Ge3S7, and Ge5As38S57. This report also describes the spectrophotometric technique utilized to determine the optical parameters.