Optical coatings on large telescope mirrors (Conference Presentation)

Advanced telescope mirror coatings have become essential for enabling new and exciting astronomical discoveries. With their ability to maximize reflectivity, reduce scattering, withstand aggressive environments, and optimize specific optical properties, advanced thin film deposition systems help telescopes to see farther and fainter with less light than ever before. This paper discusses various types of film stacks and coating technologies that can be used for demanding coating applications. An overview of challenges with different system configurations will be discussed along with practical solutions to enable uniform, high performance, coatings on large mirrors. The suitability of various mirror coating technologies, such as filament evaporation, electron beam evaporation, and magnetron sputtering, will be discussed and compared for specific mirror coating applications. Hardware design challenges, including source placement, mask and uniformity optimization, and shutter reliability, will be evaluated. Prevalent issues with mirror handling, particles, and long-run reliability will also be discussed in detail.