Polarization Beam Splitter Based on MMI Coupler With SWG Birefringence Engineering on SOI

We demonstrate a novel polarization beam splitter (PBS) based on a subwavelength grating (SWG) multimode interference (MMI) coupler for the silicon-on-insulator platform. The birefringence of the MMI coupler is engineered using SWG, which leads to a compact design footprint, with a device length of less than 100 μm. Our PBS has simulated extinction ratios (ERs) better than 20 dB for both polarizations over the wavelength range from 1530 to 1625 nm that covers the entire Cand L-bands. The fabricated device achieves the measured ERs larger than 20 dB at the wavelength of 1550 nm for both polarizations, and the insertion losses of 1.9 and 2.5 dB for the transverse electric (TE) and transverse magnetic (TM) polarizations, respectively, at 1550 nm. In addition, the measured ERs are larger than 14.5 dB for the TE polarization and 11.7 dB for the TM polarization over an 84-nm spectral range covering the entire C-band.