Directional-Coupler-Based Polarization Splitting in Asymmetric Metal/Multi-Insulator Configuration for Optical Nanocircuitry

An ultra-compact polarization splitter based on asymmetric metal/multi-insulator directional coupler is proposed and investigated analytically and numerically. A large modal birefringence of >;0.69 is estimated, enabling a clean polarization selective directional coupling within 5.6. The insertion loss of and the splitting and extinction ratios of <;-0.32 are predicted. Modified coupled-mode equations for a coupled lossy waveguide system are also presented.