Research development of high reflecting coating for large-diameter mirror

Large-diameter mirrors are the key optical elements in large aperture reflective type optical system, and the optical system performance is directly associated with the reflectance in the working wavelength region. With the great development of the ground-based and space-based observing instruments, more critical performance is required for large-diameter mirrors, such as wider wavelength region, higher reflectance, better environment durability and so on. Kinds of new coating structures, new coating methods, new coating material are emerging to the challenges, meeting the requirements of high reflecting coating for large-diameter mirror. This paper reviews the research development of high reflecting coating for large-diameter mirror home and abroad, and predicts the developing trend for preparing high reflecting coating of large-diameter reflector from Al mirror to Ag mirror as well as from thermal evaporation to magnetron sputtering.