High-Performance Silicon Polarization Beam Splitter Assisted by the Sub-Wavelength Structures

A high-performance polarization beam splitter (PBS) is proposed and experimentally demonstrated on the 220-nm silicon-on-insulator (SOI) platform. The proposed PBS consists of a sub-wavelength grating (SWG) assisted adiabatic directional coupler (ADC) and a simple filter at the through port of the ADC. The SWG structures embedded in the ADC can suppress and enhance the optical field evolutions of the fundamental TE and TM modes (referred to as TE and TM modes in short), respectively, thus enhancing the separation of these two modes. The simple filter composed of four Euler bends is used to further improve the polarization extinction ratio (PER) of the TM mode while maintaining low insertion loss (IL) for the TE mode. The simulated results show that our proposed PBS possesses the high performance of IL < 0.3 dB and PER > 30 dB for both the TE and TM modes over the bandwidth of 1.46-
$1.625~\mu \text{m}$
, which covers the most important S, C, and, L bands for optical communications. The experimental results show that the fabricated PBS has excellent performance of IL < 0.8 dB and PER > 24.5 dB over the bandwidth of 1.53-
$1.61~\mu \text{m}$
.