High-efficiency single-etch grating coupler on a hybrid α-Si/SiN photonic platform

We present the design of a high-efficiency silicon nitride grating coupler with an amorphous silicon overlay. The device combines subwavelength engineering with phase apodization. We anticipate a peak coupling efficiency of -1.2 dB and a 1-dB bandwidth of 30 nm centered at 1310 nm.