On-chip passive pump-rejection long-pass filters for integrated SiC-based nonlinear and quantum photonic chips

We present an on-chip passive pump-rejection filter on an integrated silicon carbide (SiC)-on-insulator photonic platform. Our filters exploit the optical absorption from an amorphous silicon (α-Si) thin-film layer deposited on the top surface and on the sidewalls of the SiC waveguide to reject light with a wavelength below 1.0 µm. The filter has a simple design and can be readily fabricated using a standard semiconductor wafer fabrication process and can be integrated as a pump-rejection filter component for SiC-based nonlinear and quantum photonic chips. We experimentally demonstrate a pump-rejection efficiency exceeding 230 dB/mm for 780 nm wavelengths, while we extract an insertion loss of ∼1 dB for the O-, C-, and L-bands.