Design and analysis of polarization splitter based on a horizontal slotted waveguide

We theoretically analyze the effective indices of a horizontal slotted waveguide on SOI platform. Based on the analysis, both polarization independent and strongly birefringent waveguides can be constructed in our proposed waveguide geometry. Utilizing the strongly birefringent waveguide, an ultra-compact polarization splitter based on a directional coupler (DC) was proposed and subsequently optimized by 3D-beam propagation method. The simulation results suggest that the coupling length of the DC could be less than 18 μm, and the maximum polarization crosstalk less than −47 and −37  dB for the cross and bar ports, respectively. Around the 1550 nm operating wavelength, a bandwidth of 30 nm is obtained for the crosstalk less than −20  dB. Finally, the tolerance of the splitter is discussed.