Modeling techniques for anisotropic diffraction gratings

Abstract

Diffraction gratings are often used in fiber-optic telecommunication, especially as wavelength (de)multiplexers and three-dimensional micro-optical coupling devices. The use of diffraction gratings made out of anisotropic materials is particularly attractive when trying to design high efficiency, polarization insensitive components. We show that by incorporating perpendicular grating structures of subwavelength dimensions, it is possible to enhance or reduce the polarization dependence of a traditional grating structure. This three-dimensional, form birefringent structure is analyzed with the use of rigorous coupled wave analysis (RCWA) and effective medium theory (EMT). The application of other analytical techniques, such as the coordinate transformation method and the classical differential method, are discussed, in the context of this particular type of grating structure. We present grating structures in which it is possible to enhance or reduce the polarization dependence of the diffraction efficiency, in a given wavelength range.