Symmetry properties of lossless diffraction gratings

Abstract

Several conservation relations for lossless diffraction gratings, relying upon the symmetry of the structure, are devised for two specific configurations, 1) the long wavelength case for which only the zeroth orders are propagating, and 2) the first order Littrow mount for which only the zeroth and first orders are propagating. The principle of time reversibility has been used to derive general properties applying not only to the propagating plane waves but also to evanescent waves and modal field quantities.