Demonstration of a compact bilayer inverse taper coupler for Si-photonics with enhanced polarization insensitivity.

We demonstrate a compact (30 μm long) broadband bilayer inverse taper edge-coupler for silicon photonics with a 1.7 dB coupling loss from a commercially available focused fiber with 5 μm mode diameter. We compare the performance of our bilayer taper with a conventional SOI inverse taper coupler and show that our bilayer coupler achieves between 1.5 dB to 2 dB improvement in the coupling efficiencies for both the TE and TM polarizations. The dimensions and fabrication steps for our bilayer taper are simple and compatible with standard foundry processes.