Abstract

The rigorous coupled wave theory can be used to describe accurately all physical phenomena associated with diffraction gratings. In this paper a planar diffraction grating with the average dielectric constant larger than that of the surrounding space is treated. In particular, the resonance behavior of the diffracted fields in this structure is studied. As the grating thickness or the incident angle are varied, it is shown that waveguide modes are excited. These modes can cause rapid variations in the intensities of the external propagating diffracted waves. For weakly modulated, relatively thin gratings, the ordinary waveguide eigenvalue equation accurately predicts the occurrence of the resonances. As the modulation or waveguide thickness increases, deviations arise.

© 1989 Optical Society of America