Compact ultrabroadband polarization beam splitter on silicon nitride using subwavelength gratings

We propose and experimentally demonstrate a compact ultrabroadband polarization beam splitter (PBS) on a silicon nitride (SiN) platform. This device utilizes birefringence through Brewster-angled SiN subwavelength gratings (SWGs) to separate the transverse electric (TE) and transverse magnetic (TM) modes. The designed PBS has a compact footprint of 32 × 38 µm² for the SWG region. The PBS is fabricated using standard open-access foundry processes, and we achieve measured polarization extinction ratios (PERs) greater than 20 dB across the S+C+L band for both modes.