Surface-charge-induced electric fields in anisotropic crystals

Several classes of electronic imaging devices, such as electrooptic spatial light modulators, employ a structure that consists of a layer of dielectrically anisotropic light-modulating material and an isotropic blocking layer sandwiched between two equipotential planes. This structure is generally addressed by depositing a spatially varying surface charge distribution at the interface between the two media. In this paper, solutions for the electric potential in both media are calculated for the general case where the light-modulating crystal is biaxial and its crystallographic axes are not aligned with the geometric axes of the structure. Specific solutions for sinusoidal charge distributions at the interface are then developed from the general solution, and numerical techniques used to derive plots of the potential and the electric field distributions in the material. The results show that in highly anisotropic oblique-cut crystals, both the transverse and longitudinal field components in the crystal can exhibit non-monotonic behavior with distance away from the interface for high-frequency charge distributions.