Subwavelength apodized grating coupler for silicon photonics waveguide coupling

A high coupling efficiency grating coupler with subwavelength nanostructure for grating strength apodization is investigated for silicon photonics waveguide coupling application. Based on the 220 nm silicon-on-insulator (SOI) platform with 70 nm shallow etch and 160 nm poly-silicon overlay, maximum coupling efficiency of -1.72dB at 1550 nm wavelength and 1 dB bandwidth of 42 nm are achieved without the use of any back-reflector.