Optical Glass Bk7/K9, Fused Silica Flat/Concave/Convex Mirror with Dielectric Coating
29 Sep 2022
The purpose of optical coatings is to change the reflectivity of optical surfaces. According to the materials and physical phenomena which are used one can in principle distinguish metallic and dielectric coatings. Metallic coatings are used for reflectors and neutral density filters. The reflectivity which can be achieved is given by the properties of the metal. Dielectric coatings use, however, optical interference to change the reflectivity of the coated surfaces. Another major difference is that the materials used for this kind of coatings show very low absorption. Using optical interference coatings the reflectivity of optical surfaces can be varied from nearly zero (anti reflection coatings) to nearly 100% (low loss mirrors with R > 99.999%). However, these reflectivity values are achieved only for a certain wavelength or wavelength range.