Compact silicon-based TM-pass/TE-divide polarization beam splitter using contra-directional grating couplers assisted by horizontal slot waveguide

A compact silicon-based TM-pass/TE-divide polarization beam splitter based on contra-directional grating couplers (CDGCs) is proposed, where two identical corrugated strip waveguides are located at both sides of a central slot waveguide with corrugations on the bottom silicon layer. The waveguide widths are optimized so that only TE mode can satisfy the contra-directional coupling condition. The TE mode will be contradirectionally coupled to the corrugated strip waveguides by using CDGCs, and the final outputs from the two drop ports will be equal. The TM mode is hardly affected and direct passes through the central slot waveguide, the outputs at two drop ports are nearly negligible due to large phase mismatch. The coupling length of the designed device is 14 mu m. The simulation results at the central wavelength of 1550 nm indicate that, the extinction ratio is 38.4 dB (20.9 dB) and the insertion loss is -3.26 dB (-0.14 dB) for TE (TM) mode. Besides, the fabrication tolerances and the power distribution along the propagation direction are presented.