Ultra-high extinction ratio polarization beam splitter using an antisymmetric grating-assisted multimode waveguide

Abstract

We have proposed and demonstrated a polarization beam splitter (PBS) with an ultra-high extinction ratio (ER) utilizing an antisymmetric grating-assisted multimode waveguide (AGMW) and an asymmetric directional coupler (ADC) on a silicon-on-insulator (SOI) platform. The AGMW structure is designed to facilitate the conversion of the forward TE0 mode into the backward TE1 mode. Upon injection of the TE0 mode, it transforms into the backward TE1 mode, subsequently undergoing conversion back to a TE0 mode through the ADC and ultimately dropping out from the designated port. In contrast, the injected TM0 mode traverses the device with minimal impact. The simulation results indicate that, for the TE0 mode, a bandwidth of 70 nm with an insertion loss (IL) below 0.65 dB and an ER over 40 dB is achieved. Similarly, for the TM0 mode, the bandwidth with the IL below 0.13 dB and an ER over 40 dB is 90 nm. Experimental validation confirms that, within the measured wavelength range from 1500 to 1580 nm, the bandwidth with an ER exceeding 30 dB is 61 nm for the TE0 mode and 78 nm for the TM0 mode.