Abstract

To account for the detailed properties of diffraction gratings, an exact electromagnetic model is necessary. We have recently used such a model, the rigorous coupled-wave theory, to study the guided-mode resonance properties of planar dielectric-layer diffraction gratings.¹ Earlier related work was done by Hessel and Oliner.² In this paper, the guided-mode resonances of strip gratings with rectangular grating shape placed on arbitrary substrates are treated. To observe the resonances, the strip grating must have an average permittivity larger than that of the cover region and the substrate (waveguide-like structure). If the permittivities composing the adjacent half-periods of the grating have similar magnitudes, the homogeneous waveguide eigenvalue equation may be used to predict the resonance locations. If this difference is large, as it often is in practice, numerical calculations must be used to obtain the resonance behavior. Calculated results for both cases are presented in this paper, and the resonance properties of bulk and surface-relief gratings are compared.

© 1990 Optical Society of America