Realization of a compact broadband polarization beam splitter using the three-waveguide coupler

A compact broadband polarization beam splitter is designed and experimentally demonstrated based on a silicon-nitride-assisted three-waveguide coupler. With the help of coving a layer of silicon nitride on the center bridged silicon waveguide, the phase matching is met for the TM mode but not for the TE mode. The final optimized device length is only 7 μm, and the polarization beam splitter has the high extinction ratios of more than 30 dB for the TE mode and that of more than 20 dB for the TM mode in the wavelength ranging from 1.5 μm to 1.6 μm. And the corresponding insertion losses are less than 0.06 dB and 0.35 dB, respectively. The experimental measurement results also show the polarization beam splitter has good performances.