Abstract

Optical scatter characteristics were measured for high-reflectance (HR) dielectric thin films and polished fused-silica (FS) substrates. The measurements show lower scatter for thin films deposited on superpolished substrates than for identical films on conventionally polished substrates, and less scatter for uncoated superpolished surfaces than for conventionally polished surfaces. Scatter was also greatly affected by the design, the materials, the deposition process, and the process used to clean the substrates. The scatter characteristics were not improved by CO₂ laser cleaning¹ of the substrate prior to film deposition. Measurements were made at the design wavelengths of the thin films (i.e., 633 and 1320 nm) and consisted of bidirectional reflectance distribution function (BRDF) angle scans and spatial mappings.²

© 1992 Optical Society of America