Efficient Unidirectional Optical Coupling for Hybrid Plasmonic Waveguide

A new type of efficient and unidirectional optical coupler composed of periodic nanoslits milled in the metallic surface is proposed for the hybrid plasmonic waveguides. The operation principle is clarified and theoretically illustrated by using the coupled-mode model and the fully vectorial aperiodic Fourier modal method. The coupling efficiency of more than 50% and splitting ratios better than 18 dB at the incident angle θ= 12° could be achieved over the C-band ranging from 1530 to 1570 nm.