PERFECT BLAZING FOR TRANSMISSION GRATINGS

Using electromagnetic theory, we first establish that a triangular-groove dielectric grating can be optimized to concentrate all the transmitted energy into only one transmitted order. This is done by evaporating an infinitely thin layer of a perfectly conducting metal on the small facet of the grooves. The +l-order transmitted efficiency then approaches 96%, the difference from 100% being due to only the Fresnel normal reflection on the large facet. Second, a similar study is conducted with an antireflection coating added to the large facet. A diffraction efficiency of 100% is then theoretically obtained. © 1990 Optical Society of America.