Compact PSR Based on an Asymmetric Bi-level Lateral Taper in an Adiabatic Directional Coupler

We propose a compact silicon-on-insulator polarization splitter-rotator (PSR). The PSR consists of an asymmetric bilevel lateral taper in an adiabatic directional coupler and convert TM0mode to TE0mode directly without changing the input TE0mode. Compared to the previously reported PSR based on TM0-TE1polarization rotator connected to a TE1-TE0spatial mode order convertor in series, the proposed PSR has a one-step mode conversion, and is inherently more compact. Beside, since the conversion is fully adiabatic, it preserves the benefits of large fabrication tolerance and operation bandwidth. The simulation results show that the TM0-TE0polarization conversion loss is less than 0.5 dB from 1500 to 1700 nm and even less than 0.2 dB over the whole C-band. The TE0-TE0insertion loss is less than 0.01 dB from 1450 to 1750 nm. The polarization crosstalk is below -35 dB within 300-nm bandwidth.