Ultra-broadband, polarization-insensitive SMF-28 fiber edge couplers for silicon photonics

We have designed, fabricated and tested edge couplers for silicon photonics targeting industry-standard SMF-28 fibers. These edge couplers are based on a SiN inverse taper fabricated on a silicon-on-insulator (SOI) platform combined with an etch-based substrate removal process that prevents leakage of the expanded mode to the underlying silicon substrate. The measured couplers exhibited a 0.5 dB bandwidth exceeding 100 nm, polarization dependent loss (PDL) of less than 0.5 dB and coupling efficiency of approximately −3 dB in O-band. Similarly, a 1 dB bandwidth exceeding 100 nm, PDL less than 1 dB and coupling efficiencies of −3 dB and better than −4 dB for TE and TM modes respectively were demonstrated across the C- and L-bands.