Pure coupled mode analysis of diffraction by isotropic transmission volume gratings

The idea of pure coupled mode approach is extended to the analysis of volume grating structures. In this approach, diffraction orders inside the grating are expanded over TE and TM components and unperturbed wavevectors are used instead of Floquet wavevectors of conventional coupled wave approach. Coupling between these orders are considered to model the diffraction. Three-dimensional grating structures are analyzed, and comparisons with rigorous coupled wave analysis are made to verify the accuracy and determine the range of applicability of the proposed method.