Fig. 1. Cross-sectional schematics of multilayer SNSPDs with (a) two- and (c) three-layer superconducting nanowires. The detector structure includes the following: (bottom to top) Si substrate, Al, SiO2 layer, and multiple-layer superconducting nanowires. The total absorption (red line) and separated absorption of each layer nanowire of multilayer SNSPDs with (b) two- and (d) three-layer nanowires.

Fig. 2. SEM image of the active area of a bilayer nanowire detector. The inset shows the magnified image of the nanowire. The device diameter, the nanowire width, and the nanowire pitch are 15 μm, 80 nm, and 160 nm, respectively.

Fig. 3. (a) SDE versus bias current at different wavelengths (the dark square line is DCR as a function of bias current). (b) SDE as a function of wavelength from 500 to 1700 nm (blue line), and the red line is the simulated absorptance for comparison.

Fig. 4. (a) Histogram of time-correlated photon counts measured at a wavelength of 1550 nm (blue circle; the red line is the fitted curve using Gaussian distribution). (b) Oscilloscope persistence map of the response at a bias current of 14.5 μA.

Fig. 5. Autocorrelation function G(τ) at the bias current of 14.5 μA.