Some aspects of optical coatings in China

Abstract

Up to thirty more years ago one could not find any optical coatings work in China. In the early nineteen fifties Prof. Zenglu He, the former director of the Department of Physics at the Zhejiang University, and his co-workers began to work on optical thin films. Since no vacuum equipment was available at that time, they first had to design and build coating machines, including glass vacuum systems and glass bell jars. They were some of pioneers in this field in China. Since then many optical coatings laboratories were founded in Changchun, Shanghai and other places with purpose of developing multi-layer optical coatings. Nowadays several hundreds thin film people are working in this field, mostly in research institutes and universities in Shanghai, Beijing, Changchun, Chengdu and Hangzhou etc. Their efforts are mainly concentrated on preparing various thin film optical filters for practical applications in optical and laser engineering. The following coatings, such as narrow band filters with center wavelengths from 0.20 to 20 μm, high quality laser mirrors with reflectance of 99.9% at the wavelength 632, 8nm, polarized beam spilitters with extinction ratio up to 300:1, visible and infrared circular variable filters, unprotected cold mirrors, wide band heat reflectors, color seperation filters, multilayer antireflection coatings and many more others have been produced. Almost all types of optical coatings can be produced today in many research institutes and universities only for their own projects. This indicates a significant progress in this field in China. However, most of complex optical coatings are not commercially available so far. Many optical companiesonly produce simple antireflection coatings and metallic mirrors in their production lines.