Dual-band multiplexer/demultiplexer with photonic-crystal-waveguide couplers for bidirectional communications

An ultrashort photonic-crystal-waveguide (PCW) coupler is numerically designed for dual-band multiplexing/demultiplexing (Muxing/Demuxing). The PCW coupler consists of two line defects of reduced rods in a triangular lattice and Muxing/Demuxing is implemented by the distinction between coupling and decoupling of PCWs. Since waves tend to highly localize within the reduced rods, the backward coupling is suppressed and the efficiency of Muxing/Demuxing is enhanced as compared with the void-rod PCWs. The coupler is utilized to build a bidirectional system for dual-band duplex communications.