Compact single-etched sub-wavelength grating couplers for O-band application

We demonstrate two single-etched sub-wavelength grating coupler (SWGC) designs for O-band application, one targeting at high coupling efficiency and the other targeting at broad operating bandwidth. The high-efficiency SWGC has a measured peak coupling efficiency of 3 : 8 dB and a 3-dB bandwidth of 40 nm, and the broadband SWGC has a measured peak coupling efficiency of 4 : 3 dB and a 3-dB bandwidth of 71 nm. Focusing gratings have been used in our SWGCs to reduce the design footprints and the dimensions of our SWGCs are smaller than 45 mu m X 24 mu m. The back reflections of our SWGCs are suppressed to be below 15 dB over the wavelength range from 1260 nm to 1360 nm. (C) 2017 Optical Society of America