Abstract

The transmittance and reflectance of dielectric and lossy surface-relief gratings in the limit of periods small compared to the incident wavelength are determined for an incident wave of arbitrary angle of incidence and polarization. The orientation of the plane of incidence is also arbitrary; it may contain the grating vector, be normal to the grating vector, or have some other orientation. In the small period limit, all diffracted orders except the zeroth order are cut off, and the grating behaves like a slab of uniaxial material with the optic axis parallel to the grating vector. The refractive indices of the slab are determined by the grating filling factor and the indices of the substrate and surrounding medium. We compare the diffraction efficiencies predicted by this model with those obtained by the rigorous coupled-wave analysis. The wavelength-period ratio necessary for the validity of this model is determined, and we show that antireflection behavior can be obtained by appropriate combinations of groove depth and filling factor.

© 1992 Optical Society of America