Compact polarization beam splitter assisted by subwavelength grating in triple-waveguide directional coupler

A polarization beam splitter (PBS) is one of the key components for manipulating different polarization states in the areas of optical interconnection and communication. In this paper, a PBS with two coupling regions using a subwavelength grating (SWG) waveguide as a bridge is proposed and investigated on a 340-nm silicon-on-insulator platform. The PBS is designed with a triple-waveguide directional coupler consisting of two identical silicon waveguides and an SWG waveguide sandwiched between them. The tailorable dispersion relation of the SWG waveguide offers a flexible design freedom. With the optimized grating period and duty ratio, the input TE mode will experience efficient coupling between the silicon waveguide and the SWG waveguide, while the TM mode can directly pass through without influence. The results show that with a device length of 6.5 μm, the extinction ratios and insertion losses of the two modes are higher than 27 dB and lower than 0.3 dB at a wavelength of 1550 nm, respectively.