A monolithically fabricated apodized a-Si:H grating coupler with metal mirror was demonstrated. The minimum groove length for the apodized grating was more than 100 nm and measured coupling efficiency was 70%.
Inter-layer grating couplers sandwiched by two metal layers were demonstrated for high coupling efficiency vertical coupling between amorphous-Si:H multi-stacked optical waveguides. A coupling efficiency of 83% was achieved with grating couplers formed on 5 μm wide waveguides separated by 1 μm while theoretical coupling efficiency of 90% was obtained.
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