Fig. 1. "Hotspot" model detection mechanism of SNSPD^[10]

Fig. 2. Three methods to improve system detection efficiency. (a) Effectively improving optical coupling efficiency by using lens fibers^[11]; (b) absorption efficiency with different optical structures and can be improved to 100% with distributed Bragg reflector^[12]; (c) response efficiency is improved to 100% by WSi material with lower energy gap^[13]

Fig. 3. DCR. (a) Variation curves of SNSPD dark counting rate with bias current at different temperatures [inset: curves of DCR with (black cross) and without fiber optic (red circle) as a function of bias current]^[19]; (b) commercial SNSPD device with high SDE and low DCR

Fig. 4. Comparison of timing jitter between SNSPD and SPAD^[20]

Fig. 5. Non-invasive in vivo confocal microscopy of intact mouse head in NIR-II window^[29]

Fig. 6. Performance comparison of FILM based on PMT and SNSPD^[33]

Fig. 7. Autocorrelation functions^[35]. (a) Rhodamine B; (b) Rhodamine 6G

Fig. 8. Single line oxygen fluorescence detection system based on SNSPD^[38]

Fig. 9. Diffuse reflectance correlation spectroscopy system based on SNSPD. (a) Schematic diagram^[44]; (b) comparison of instrument response function, time-of-flight, and auto-correlation function of SNSPD and SPAD^[46]

Fig. 10. Infrared detector array structure. (a) N×M array^[50]; (b) parallel nanowire array^[21]; (c) superconducting single-photon imaging array based on delay line^[51]

Fig. 11. Commercial SNSPD detection system QEye physical image. (length is 600 mm, width is 600 mm, and height is 1250 mm)

Table 1. Performance of global SNSPD companies