Demonstration of an on-chip broadband polarization splitter and rotator using counter-tapered coupler

A broadband and fabrication-tolerant polarization splitter and rotator (PSR) using a counter-tapered coupler is proposed and demonstrated on silicon-on-insulator (SOI) platform. Compared to previously reported PSRs based on a conventional directional coupler, which suffer from relatively low bandwidth and stringent fabrication requirements, the introduced counter-tapered structure can be used to enlarge the bandwidth and fabrication tolerance. The proposed PSR can be fabricated through a single step of lithography and etching, with a total length of 170μm. The measured results show that the fundamental transverse magnetic (TM0) to fundamental transverse electric (TE0) polarization conversion loss is less than 0.8 dB, while the TE0-TE0 insertion loss is less than 0.5 dB, over the wavelength range from 1520 to 1580 nm. The polarization crosstalk is lower than -20/-18 dB for TE0/TM0 mode, respectively.