Advances in optical coating uniformity of interference filters

Abstract

We propose a method to obtain uniform multilayer coatings using vacuum assemblies with a linear ion source to manufacture narrow-band interference filters essential in astrophysical research for space object imaging in important spectral lines, and to provide multi-channel fiber-optic transmission of information. Interference filters and other optical systems, for example, high-reflective mirrors, steep-front beam splitters contain up to hundreds of film layers deposited onto a substrate. During the coating deposition, film thickness on the substrate must be strictly withstood and be uniform throughout the entire surface. This can be achieved by placing the linear source and target on the same platform and by conducting a test target sputtering on a fixed substrate. There is an inflection line on the coating thickness distribution on the substrate. By moving the platform, the inflection line midpoint is aligned with the center of the rotating working substrate, and in this position, the substrate is coated to a specified thickness, which is monitored during the deposition process.