Suppressing Dark Counts of Multimode-Fiber-Coupled Superconducting Nanowire Single-Photon Detector

Abstract

Large active-area superconducting nanowire single-photon detectors (SNSPDs) coupled with multimode fibers (MMFs) can provide high light-gathering capacity, which is essential for free-space detection applications in photon-starved regimes. However, MMFcoupled SNSPDs often suffer from large system dark count rates (DCR sys) over kHz due to blackbody radiation of the MMF at room temperature. Such large DCR sys would significantly degrade signal-to-noise ratio (SNR) of the receiving system. This paper reports an MMFcoupled large-active-area SNSPD system with low DCR sys by using a homemade cryogenic MMF filter bench. The filter bench, which consists of lenses and optical filters, can provide a high transmittance of about 80% at the central wavelength of the passband (1550 ± 12.5 nm) and a wide blocking range from 500 nm to over 6000 nm at 40 K. With using the filter bench, the DCR sys of an MMF-coupled 9-pixel SNSPD array with an active area of 50 μm in diameter is greatly suppressed by 23 dB with 1 dB loss of system detection efficiency (SDE). The detector demonstrates an SDE of 51% at a DCR sys of 100 Hz for 1550 nm photons. Thus, SNR of the detector is enhanced by about 160 times and the noise equivalent power is improved to 3×10 −19 W/Hz 1/2 .

Superconducting microstrip single-photon detector with system detection efficiency over 90% at 1550 nm

“…However, according to our knowledge, this SDE is still the highest value reported for the MMF-coupled detectors at 1550 nm. Meanwhile, owing to the broadband background radiation transmitted by the MMF coupling, a significantly raised DCR was observed, which can be suppressed using cold narrowband filters, e.g., a MMF-coupled filter bench [34]. Through Gaussian fitting, TJ of ~50 ps at I b = 95 µA is obtained, which is slightly different compared to that of the SMF coupling due to the fiber-associated dispersion in optical signal transmission in MMF [35].…”

16-Element Superconducting Nanowire Single-Photon Detector for Gigahertz Counting at 1550-nm

“…This multi-element device showed 83.4% net system detection efficiency with 71,000 dark counts per second, average per-pixel timing jitter of 86.1 ps FWHM, and average perpixel reset time of 9.675 ns-meaning the device can count with > 50% system detection efficiency at 1GHz mean photon rate. Dark counts are elevated above standard commercial SNSPDs due to the FMF-coupling, these could be drastically reduced by coupling the device to SMF (which achieves dark count rates of <100 /s on standard commercial devices) or by using cold filtering techniques 25 . We expect that increasing availability of this type of high-count rate, high efficiency, SNSPD will drive new applications in many fields.…”

Superconducting nanowire single-photon detector: a rising light sensor for bio-fluorescence imaging and microscopy

“…The DCR and FCR could be further reduced by placing a cold filter inside the chip package to filter out the black-body radiation coupled into the MMF. 33 The lowest timing jitter of this particular device is 35 ps, measured in the same way as we used in characterization of SMF-coupled fractal SNSPDs. Compared with the results of the SMF-coupled fractal SNSPDs, the MMF-coupled fractal SNSPD exhibits no significant deterioration on DCR, FCR, or timing jitter, which can be attributed to the relative small photo-sensitive area we used.…”