Compact Polarization Beam Splitter for Silicon-Based Slot Waveguides Using an Asymmetrical Multimode Waveguide

A compact polarization beam splitter (PBS) for silicon-based slot waveguides is proposed, where an asymmetrical multimode waveguide (AMW), cut by a right angle at one corner, is employed to efficiently separate the TE and TM modes. With the unique modal properties of the slot waveguides, the input TE mode almost passes through the AMW and enters into the bar port, while the input TM mode forms a mirror image at the cross port due to the self-imaging effect. Tapered waveguide structures and S-bend are incorporated into the PBS for enhancing the performance. Results show that a PBS with an AMW of 2.3 μm in length is achieved, where the extinction ratios are 16.6 and 20.9 dB, respectively, for TE and TM modes, and the insertion losses are 1.37 and 0.81 dB, respectively, at the wavelength of 1.55 μm, and the bandwidths can cover the entire C-band for both polarizations. In addition, fabrication tolerances to the structural parameters are investigated and field evolution along the propagation distance through the designed PBS is also demonstrated.