Abstract
The theory of double-layer antireflection coatings using non-quarter-wave films is reviewed and extended. Normal incidence only is considered. The spectral reflectance of a double-layer coating depends on the refractive indices of the layers and the adjacent media, and on ø1and ø2, the phase thicknesses of the layers. It is known that the reflectance is theoretically zero if the refractive indices satisfy certain inequalities and if the phase thicknesses are those calculated from certain equations.