Efficient silicon nitride grating coupler with a dielectric multilayer reflector

A highly efficient grating coupler with a dielectric multilayer reflector for silicon nitride photonic integrated circuits was proposed. Design, fabrication and optical characterization were presented. The peak coupling efficiency and 3 dB bandwidth are -4.5 dB and 68.0 nm, respectively. The fabrication process is CMOS-compatible with only one etching step.