Fig. 4: Experimental setup and measurement of the coupling between the strip waveguide (SWG) and the topological waveguides (TWG). | Nature Communications

Fig. 4: Experimental setup and measurement of the coupling between the strip waveguide (SWG) and the topological waveguides (TWG).

From: Efficient coupling of topological photonic crystal waveguides based on transverse spin matching mechanism

Fig. 4: Experimental setup and measurement of the coupling between the strip waveguide (SWG) and the topological waveguides (TWG).

a Schematic of experimental setup of the measurement. Light signal from an optical fiber tip is coupled into the waveguide (TE mode) through the input grating, and then a 50/50 Y-splitter sends the signals to the optimized coupler (upper branch) and to a reference arm (lower branch). The transmitted power is coupled out from the grating and collected by another optical fiber pigtail for detection. b SEM images of the optimized sample, including the TWG and the input and output waveguides on both sides, as well as the corresponding left and right optimization areas. c Experimentally measured results, and the peak value of 94.2% around 1555 nm is obtained. d Numerically computed results, which agrees well with those of measured results.

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