Bilayer Coatings for Light Refraction Without Change of Polarization

Abstract

Wave refraction without change of polarization at a dielectric—dielectric interface is achieved with a bilayer coating of two transparent thin films. For given refractive indices of all media, the thicknesses of the two films are determined as functions of the angle of incidence. The polarization-independent reflectance and the differential reflection phase shift of the coated substrate are also calculated. Examples are presented of MgF₂—ZnS and Ge—MgF₂ bilayer coatings on a Ge substrate that refract infrared radiation without change of polarization. Such coatings are useful in the construction of polarization-preserving beam deflectors and beam splitters.