Ultra‐Broadband Reflective Polarization Beam Splitter Based on Tilted Sub‐Wavelength Gratings

Abstract Sub‐wavelength gratings (SWGs) and tilted SWGs (TSWGs) are extensively employed in polarization management of silicon photonics due to their excellent flexibility and scalability. However, the complex structure of most SWG‐assisted polarization beam splitters (PBSs) presents challenges in manufacturability. In this study, a reflective TSWG structure, compatible with slab waveguides for polarization beam splitting, is presented and implemented in a TSWG‐assisted PBS. Transverse magnetic (TM) polarization is transmitted through the TSWG structure, whereas transverse electric (TE) polarization undergoes total internal reflection (TIR) at the TSWG's surface. Benefiting from the distinctive design of the TSWG, which facilitates TIR for the TE mode within the slab waveguide, only a minimal number of TSWG periods is required to achieve effective polarization splitting, markedly simplifying device complexity. Experiment results indicate that the proposed PBS exhibits an extinction ratio (ER) of 36.7 dB at 1550 nm, and greater than 20 dB over an ultra‐broad bandwidth of 279 nm. Within ±10 nm fabrication errors, ERs maintain above 30 dB at 1550 nm wavelength, demonstrating an exceptional robustness. Furthermore, for various application scenarios, we confirm that the design can be adjusted by tuning the structural parameters, offering a highly flexible solution.