Asymmetrically and Vertically Coupled Hybrid Si/GaN Microring Resonators for On-Chip Optical Interconnects

A working small-footprint asymmetrically and vertically coupled hybrid Si/GaN microring resonator (HMR) was demonstrated. The HMR of a minimum radius of 20 μm was fabricated in a high-yield (~90%) hybrid nanophotonic platform that allowed interactions between the GaN microring and the underlying Si waveguide circuit. The HMR's spectral response across the telecommunication C- and L-bands was measured. The high extinction ratio of up to 17 dB, the resonance linewidth as narrow as 40 pm, and the intrinsic quality factor of up to 70 000, which was the highest value for GaN microring reported so far, were achieved. The explicit analytical model for the high-index-contrast HMR was developed. Our basic study opened new possibilities for exploring GaN-Si nonlinear phenomena and for developing complex on-chip optical interconnects.