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

• Published in: IEEE photonics journal 2019-10, Vol.11 (5), p.1-8
• Main Authors: Zhang, Chengjun, Zhang, Weijun, You, Lixing, Huang, Jia, Li, Hao, Sun, Xingqu, Wang, Heqing, Lv, Chaolin, Zhou, Hui, Liu, Xiaoyu, Wang, Zhen, Xie, Xiaoming
• Format: Article
• Language: English
• Subjects: Band-pass filters; Black body radiation; Detectors; Nanowires; Optical fiber filters; Optical filters; Photonics; Photons; Sensors; Signal to noise ratio; Superconductivity; Temperature measurement
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2019.2937537

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, MMF-coupled 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 MMF-coupled 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 .