Fig. 1. One-side cavity model and calculated absorption efficiency of the nanowire absorber. (a) Schematic of the lossy cavity with an embedded nanowire absorber; (b) calculated nanowire absorption spectrum for varying photon loss per round trip in the cavity. The cavity length is fixed at L=1/4(λ/neff). (c) Calculated nanowire absorption spectrum for varying cavity length. The photon loss per round trip is fixed at α2=−1.0  dB.

Fig. 2. Comparison between HIC and MIC waveguides. Cross-sectional schematics and simulated mode profiles of (a) MIC and (b) HIC waveguides. Scale bars, 200 nm; simulated nanowire absorption rates as a function of waveguide width for (c) MIC and (d) HIC waveguides of varying thicknesses.

Fig. 3. Simulated nanowire absorption rates depending on the nanowire width and thickness for the optimized HIC waveguide design.

Fig. 4. Effect of the waveguide types and geometry on the nanowire absorption rates. Cross-sectional schematics of (a) air-cladding waveguide on SiO2, (b) SiO2-cladding buried waveguide, and (c) fully suspended waveguide. (d)–(i) Simulated nanowire absorption rates depending on the waveguide geometry for HIC waveguides with various upper and bottom claddings of different indices. The corresponding simulation results are shown in the same column as the schematics of the waveguides.

Fig. 5. H0-type PhC cavity design and optimization. (a) Schematic illustration of the H0-type PhC cavity formed by slightly shifting two air holes away from their original positions. a, r, and s denote the lattice constant, hole radius, and the amount of hole shifts, respectively. (b) Simulated electric field distribution of the H0-type PhC cavity at the resonant wavelength; scale bar, 200 nm. (c) Simulated intrinsic quality factor Qi and resonant wavelength of the H0-type PhC cavity versus s/a for varying value of a.

Fig. 6. Nanowire absorber integrated with H0-type PhC cavity. (a) Schematic of the H0-type PhC cavity with front partial mirror consisting of two smaller air holes. (b) Schematic of the H0-type PhC cavity with two arc-shaped nanowires embedded inside. (c) Simulated coupling quality factor Qc of the H0-type PhC cavity as a function of the number and the radius of the coupling holes. The blue dashed line represents the absorption quality factor Qa of the cavity with the nanowires loaded. (d) Simulated electric field distribution of the critically coupled H0-type PhC cavity at the resonant wavelength. (e) Simulated power dissipation density in the nanowires at the resonant wavelength. (f) Simulated dependence of the nanowire absorption on the wavelength for varying coupling hole sizes. The FWHM defining the 3 dB bandwidth of the nanowire detector at the critical coupling condition is marked by a pair of purple arrows; all scale bars, 200 nm.

Table 1. Summary and Comparison of SNSPDs with Different Device Structures