High coupling efficiency dual-wavelength band waveguide grating couplers

We present a high-efficiency dual-wavelength band waveguide grating coupler (DWBGC) utilizing an optimized shifted polysilicon overlay grating above a conventional silicon grating. This design enables efficient coupling of O-band and C-band light into opposite directions by a single grating. Simulations predict coupling efficiencies of −2.17 dB (O-band) and −1.65 dB (C-band) with 1 dB bandwidth of 30 nm and 40 nm, while the experimental results achieved −2.79 dB and −2.28 dB with 1 dB bandwidth of 27 nm and 33 nm, respectively. The proposed DWBGC achieves high efficiency without requiring bottom metal reflectors and is fully compatible with standard photolithography processes used in large-scale silicon photonics manufacturing.