Experimental Demonstration of High-Efficiency Silicon Nitride Grating Couplers for O-Band Applications

Silicon nitride offers a broad transparency window and low losses that make it a complementary alternative to silicon-on-insulator. The moderate refractive index contrast of the silicon nitride platform reduces the efficiency of fibre-chip coupling devices. This study presents high-efficiency grating couplers designed for the 1310 nm wavelength regions. Our devices are compatible with a single full-etch step fabrication process. Enhanced performance is predicted through subwavelength metamaterial apodization and beam focalization.