Photolithography Fabricated Sub-Decibel High-Efficiency Silicon Waveguide Grating Coupler

Using the optimized shift-pattern overlay method, we present a new high-efficiency silicon waveguide grating coupler operating at 1550 nm center wavelength, which has a simulation predicted coupling loss of 0.68 dB and experimentally measured loss of 0.89 dB. This record result was achieved without any substrate bottom mirrors or use of electron beam lithography and was fabricated with the standard processes of a multi-project wafer fabrication service from a commercial foundry.