Multilayer antireflection coatings: theoretical model and design parameters

A theoretical model for multilayer antireflection coatings is presented on the basis of the theory of all-dielectric Fabry-Perot interference filters. Effective interfaces are employed, and a new concept of a replacement pair consisting of two layers is introduced. It is shown that incorporation of this pair in a multilayer yields low reflectance values over a wide spectral range. This theoretical model is then used to design various coatings, and three typical examples are given and discussed. The various parameters that control the reflectance behavior in the region of low reflection are also discussed.