Rigorous diffraction analysis of metallic binary gratings

Abstract

Recently, surface relief dielectric and metallic gratings have generated great interest for diffractive optics applications. High quality gratings with deep grooves and small grating periods have been recently fabricated using electron-beam technology and using holographic techniques. These gratings exhibit high diffraction efficiencies as predicted by theoretical calculations.1 In this work the rigorous coupled-wave analysis is applied to metallic binary gratings with groove depths and grating periods comparable to the wavelength of light. Two practical binary gratings are considered (a) bulk finite conductivity gratings and (b) dielectric gratings with finite conductivity metallic coatings. Diffraction characteristics, including the angular and wavelength selectivities and their dependence on groove depth, aspect ratio, and polarization are presented and compared to the diffraction characteristics of infinite conductivity gratings. The approximation of infinite conductivity is shown to give very inaccurate results.