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 TM
₀
mode to TE
₀
mode directly without changing the input TE
₀
mode. Compared to the previously reported PSR based on TM
₀
–TE
₁
polarization rotator connected to a TE
₁
–TE
₀
spatial 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 TM
₀
–TE
₀
polarization 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 TE
₀
–TE
₀
insertion loss is less than 0.01 dB from 1450 to 1750 nm. The polarization crosstalk is below –35 dB within 300-nm bandwidth.