Optimized shift-pattern overlay for high coupling efficiency waveguide grating couplers

• DOI: 10.1364/ol.464652
• Publication Date: 2022-07-13T12:30:35Z
• Authors: Xuetong Zhou; Hon Ki Tsang
• Keywords: Waveguide

We propose and validate a new, to the best of our knowledge, approach for increasing coupling efficiency waveguide grating couplers by introducing an optimized shift-patterned polysilicon overlay above silicon structure. After optimizing shifts in position duty cycles each period grating, can form composite subwavelength structures which improve both mode matching directionality coupler, enable design high-efficiency perfectly vertical coupler (PVGC) with -0.91 dB simulated efficiency. The devices are fabricated using photolithography standard commercial multi-project wafer fabrication service IMEC have measured loss approximately 1.45 dB.