A Compact Ultrabroadband Polarization Beam Splitter Utilizing a Hybrid Plasmonic Y-Branch

A compact and ultrabroadband polarization beam splitter (PBS) utilizing a hybrid plasmonic Y-branch (HPYB) on a silicon-on-insulator (SOI) platform is proposed and numerically demonstrated. The HPYB consists of a vertical hybrid plasmonic waveguide (HPW) and a horizontal HPW formed by silicon (Si) and silver (Ag) strip waveguides sandwiched with a silicon dioxide (SiO2) layer, in which the vertical and horizontal hybrid plasmonic modes (HPMs) are excited by the input transverse electric (TE) and transverse magnetic (TM) modes, respectively. The HPMs are split into different ports and coupled back to TE and TM modes to implement the polarization splitting function. A simplified and compact HPYB is robust for the HPMs' generation. The structure is wavelength insensitive since the HPMs' excitation is weakly correlated to the optical wavelengths. The simulation results show that the HPYB-based PBS has a compact footprint of $5 \times 1.8\ \mu\text{m}^2$ and an ultralarge working bandwidth of 285 nm, with the polarization crosstalk <; -10 dB and the worst-case TE (TM) mode insertion loss of -1.53 (-2.35) dB. The device also exhibits a large fabrication tolerance of 210-nm variation (from -100 to 110 nm) to the waveguide width for both polarizations.