Shortly after their inception, superconducting nanowire single-photon detectors (SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency, high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons ($<0.8\mathrm{eV}$) with high efficiency and low timing jitter has remained a challenge. To achieve unity internal efficiency at mid-infrared wavelengths, previous works used amorphous superconducting materials with low energy gaps at the expense of reduced time resolution (close to a nanosecond), and by operating them in complex milliKelvin (mK) dilution refrigerators. In this work, we provide an alternative approach with SNSPDs fabricated from 5 to 9.5 nm thick NbTiN superconducting films and devices operated in conventional Gifford-McMahon cryocoolers. By optimizing the superconducting film deposition process, film thickness, and nanowire design, our fiber-coupled devices achieved $>70\%$ system detection efficiency (SDE) at 2 μm and sub-15 ps timing jitter. Furthermore, detectors from the same batch demonstrated unity internal detection efficiency at 3 μm and 80% internal efficiency at 4 μm, paving the road for an efficient mid-infrared single-photon detection technology with unparalleled time resolution and without mK cooling requirements. We also systematically studied the dark count rates (DCRs) of our detectors coupled to different types of mid-infrared optical fibers and blackbody radiation filters. This offers insight into the trade-off between bandwidth and DCRs for mid-infrared SNSPDs. To conclude, this paper significantly extends the working wavelength range for SNSPDs made from polycrystalline NbTiN to 1.5–4 μm, and we expect quantum optics experiments and applications in the mid-infrared range to benefit from this far-reaching technology.

中文翻译：

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在 Gifford-McMahon 低温冷却器中使用具有高时间分辨率的超导 NbTiN 纳米线进行高效的中红外单光子检测

超导纳米线单光子探测器 (SNSPD) 诞生后不久，便成为领先的量子光探测技术。SNSPD 能够以接近单位的效率、高时间分辨率、低暗计数率和快速恢复时间检测单光子，其性能优于传统的单光子检测技术。然而，检测较低能量的单光子（$<0.8\mathrm{电子伏特}$) 具有高效率和低时序抖动仍然是一个挑战。为了在中红外波长实现统一的内部效率，以前的工作使用具有低能隙的非晶超导材料，但以降低时间分辨率（接近纳秒）为代价，并通过在复杂的毫开尔文 (mK) 稀释冰箱中操作它们。在这项工作中，我们提供了一种替代方法，使用由 5 到 9.5 nm 厚的 NbTiN 超导薄膜制造的 SNSPD 和在传统 Gifford-McMahon 低温冷却器中运行的器件。通过优化超导薄膜沉积工艺、薄膜厚度和纳米线设计，我们的光纤耦合器件实现了$>70\%$系统检测效率 (SDE) 在 2 μm 和低于 15 ps 的时序抖动。此外，同一批次的探测器在 3 μm 处表现出统一的内部探测效率，在 4 μm 处表现出 80% 的内部效率，为具有无与伦比的时间分辨率且无需 mK 冷却要求的高效中红外单光子探测技术铺平了道路。我们还系统地研究了与不同类型的中红外光纤和黑体辐射滤光片耦合的探测器的暗计数率 (DCR)。这有助于深入了解中红外 SNSPD 的带宽和 DCR 之间的权衡。总而言之，本文将由多晶 NbTiN 制成的 SNSPD 的工作波长范围显着扩展至 1.5-4 μm，