Silicon waveguide grating coupler for perfectly vertical fiber based on a tilted membrane structure

A grating coupler for interfacing between a silicon-on-insulator waveguide and a single-mode fiber located at a perfectly vertical direction is demonstrated based on a tilted membrane structure. The proposed design is compatible with that of conventional grating couplers for oblique fibers and facilitates mass production. A peak coupling efficiency of 28.5% and 1 dB bandwidth of 38 nm are obtained experimentally for transverse-electrics polarized light. Back reflection in the SOI waveguide is also estimated to be 1.4%. The present grating coupler for perfectly vertical fiber exhibits similar performances to the conventional grating coupler for oblique fiber concerning coupling efficiency, bandwidth, and back reflections. (C) 2016 Optical Society of America