Bidirectional Polarization Splitting Couplers Based on Dielectric-Coated Metallic Gratings

A new bidirectional polarization splitting coupler based on a metal thin film perforated with periodic slits and coated with dielectric is proposed and theoretically investigated. The back-side incident light coupled to the metal-dielectric-air waveguide is split and launched into TM plasmonic and TE photonic modes simultaneously. The operation principle is clarified and theoretically illustrated using the fully vectorial aperiodic Fourier modal method. Polarization extinction ratios better than 15 dB and crosstalk less than 15 dB are achieved for both polarizations over C-band ranging from 1530 to 1570 nm.