Photonic crystal-based compact hybrid WDM/MDM (De)multiplexer for SOI platforms.

A compact hybrid wavelength- (WDM) and mode-division (de)multiplexer (MDM) is proposed, and its performance is evaluated. The design of the device is based on 2D photonic crystals with a square lattice and Si rods. The device can multiplex two eigenmodes, TM and TM, and two wavelengths, 1550 and 1300 nm. Two identical multimode interference couplers and an asymmetric directional coupler are used in implementing both the wavelength- and mode-division multiplexing functions, respectively. To avoid back-reflections, tapers are used at waveguide junctions. The structure is compact with dimensions of 29  μm×12  μm, which is suitable for on-chip integration. Simulation results reveal that the insertion losses and crosstalks are less than -1.0927 and -11.9024  dB, respectively, for all four channels.