Design of silicon waveguide polarization beam splitter based on reversed Δβ directional coupler

We report a directional coupler type polarization beam splitter using silicon waveguides designed for 1550-1600 nm wavelengths. The device uses the coupling strength difference between the TE and TM modes. We use a reversed Δβ structure to achieve a wide operational wavelength range. The gap between the waveguides needs to be wide enough to attain a sufficient extinction ratio for the TE mode. Simulation results show that an over 100 nm operational 20 dB extinction ratio wavelength range can be attained at 1520-1620 nm wavelengths by this simple structure. The fabrication width tolerance exceeds 10 nm which is enough for foundry processes. © 2020 The Japan Society of Applied Physics.