National Research Council of Canada. Information and Communication Technologies
efficiency; optical fibers; photonic devices; photonic integration technology; refractive index; engineered surfaces; fiber chip coupling; fundamental component; photonic integrated circuits; silicon on insulator waveguide; silicon-on- insulators (SOI); single etch process; surface grating couplers; silicon on insulator technology
Surface grating couplers are fundamental components in chip-based photonic devices to couple light between photonic integrated circuits and optical fibers. In this work, we report on a grating coupler with sub-decibel experimental coupling efficiency using a single etch process in a standard 220-nm silicon-on-insulator (SOI) platform. We specifically demonstrate a subwavelength metamaterial refractive index engineered nanostructure with backside metal reflector, with the measured peak fiber-chip coupling efficiency of -0.69 dB (85.3%) and 3 dB bandwidth of 60 nm. This is the highest coupling efficiency hitherto experimentally achieved for a surface grating coupler implemented in 220-nm SOI platform.