Silicon polarization beam splitter based on cascaded multimode anti-symmetric apodized Bragg gratings for 1.55 and 2 μm wavebands

Silicon polarization beam splitters (PBS) have garnered significant interest for on-chip polarization management in optical communications and quantum applications. However, maintaining polarization extinction across disparate wavebands remains challenging, and very few on-chip polarization-handling devices can operate with ultrabroad bandwidths or in multi-wave band. Here, we present a novel PBS that can achieve an unprecedented dual-band operation with ultrahigh polarization extinction ratios (PER). The dual-band PBS function is achieved using a dual-band TE0/TE1 mode (de)multiplexer and cascaded multimode anti-symmetric apodized Bragg gratings (MASABGs). The MASABG allows for strong coupling between the TE0 and the TE1 modes. For the fabricated device, the measured bandwidths (BWs) for PER > 20 dB are ∼115 nm for the 1.55-μm band and ∼100 nm for the 2-μm band, respectively. Additionally, the measured ILs are 0.5/1.2 dB at 1550 nm and 3.1/1.1 dB at 2000 nm for TE/TM polarizations.