We demonstrate superconducting nanowire single photon detector (SNSPD) for the wavelength at around 2 μm. The linewidth of the NbN nanowire is squeezed to 56 nm to increase the intrinsic response efficiencies at longer wavelengths such as 2 μm. Serially connecting avalanche architecture is applied to increase the signal-to-noise ratio (SNR) of the response signal. Further, the optical cavity is optimized to improve the absorption of the device. A silica single-mode fiber is adopted to introduce photons to the SNSPD at a temperature of 2.25 K using a Gifford–McMahon cryocooler. The SNSPD exhibits detection efficiencies of 58%, 67%, and 63% at wavelengths of 1550, 1700, and 2000 nm, respectively, with dark count rate of ∼12 kcps, which is reduced to 2 cps when the attached fiber pigtail is all placed inside the 40-K cryostat. The detection efficiency at 2000 nm is 2.5 times greater than that of the best previously developed detector with an efficiency of 25%. Our SNSPD is promising for practical applications in molecular science and earth meteorology.

中文翻译：

---

超导纳米线单光子探测器，2μm 波长效率超过 60%

我们展示了波长约为 2 μm 的超导纳米线单光子探测器 (SNSPD)。NbN 纳米线的线宽被压缩到 56 nm，以提高在较长波长（例如 2 μm）下的固有响应效率。串联雪崩架构用于提高响应信号的信噪比（SNR）。此外，光学腔被优化以提高器件的吸收。使用 Gifford-McMahon 低温冷却器，采用二氧化硅单模光纤在 2.25 K 的温度下将光子引入 SNSPD。SNSPD 在 1550、1700 和 2000 nm 波长下的检测效率分别为 58%、67% 和 63%，暗计数率约为 12 kcps，当连接的光纤尾纤全部完成时，暗计数率降至 2 cps放置在 40-K 低温恒温器内。2000 nm 处的检测效率是之前开发的最佳检测器的 2.5 倍，效率为 25%。我们的 SNSPD 有望用于分子科学和地球气象学的实际应用。