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arXiv:2606.07140

Improved Cryogenic Photodiode Optical Biasing for Low-Noise and Low-Jitter Superconducting Nanowire Single-Photon Detectors

Jia-Hao Hu, Wei-Jun Zhang, Wen-Shuo Yu, Yu-Ze Wang, Dong-Wei Chu, Ya-Tao Peng, Hui-Qin Yu, Pu-Sheng Yuan, Ling Wu, Li-Xing You

quant-phphysics.app-phphysics.ins-detSubmitted Jun 5, 2026• Announced Jun 8, 2026• 0 citations
v1 · Jun 5, 2026v2 · Jun 15, 2026
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Abstract

We experimentally demonstrate an improved optical biasing scheme for superconducting nanowire single-photon detectors (SNSPDs), which employs a cryogenic InGaAs-InP photodiode (PD) as a local bias source. It is found that, under illumination from a stable external light source, this PD generates a stable photocurrent in a cryogenic environment (~2.3 K), with fluctuations in the photocurrent primarily attributed to fluctuations in the incident optical power. Furthermore, by screening and effectively blocking stray photons leaking from the PD, which give rise to background dark counts, we have achieved an SNSPD exhibiting an ultra-low intrinsic dark count rate of 1e-4 cps. Utilizing this improved optical biasing technique, our SNSPD achieved performance comparable to that obtained under conventional electrical biasing: a system detection efficiency of 80.7%, a background dark count rate of 32.6 cps, and a minimum timing jitter of 57.5 ps. These results indicate that cryogenic-PD-based optical biasing serves as a viable, low-noise, and low-jitter alternative to traditional electrical biasing. Moreover, this work offers useful design guidance for the future development of PD-based low-noise bias sources and for the construction of all-photonic SNSPD systems tailored for high-precision quantum photonics applications.

Comments
12 pages, 5 figures

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We experimentally demonstrate an improved optical biasing scheme for superconducting nanowire single-photon detectors (SNSPDs), which employs a cryogenic InGaAs-InP photodiode (PD) as a local bias source. It is found that, under illumination from a stable external light source, this PD generates a stable photocurrent in a cryogenic environment (~2.3 K), with fluctuations in the photocurrent primarily attributed to fluctuations in the incident optical power. Furthermore, by screening and effectively blocking stray photons leaking from the PD, which give rise to background dark counts, we have achieved an SNSPD exhibiting an ultra-low intrinsic dark count rate of 1e-4 cps. Utilizing this improved optical biasing technique, our SNSPD achieved performance comparable to that obtained under conventional electrical biasing: a system detection efficiency of 80.7%, a background dark count rate of 32.6 cps, and a minimum timing jitter of 57.5 ps. These results indicate that cryogenic-PD-based optical biasing serves as a viable, low-noise, and low-jitter alternative to traditional electrical biasing. Moreover, this work offers useful design guidance for the future development of PD-based low-noise bias sources and for the construction of all-photonic SNSPD systems tailored for high-precision quantum photonics applications.
Superconducting Nanowire Single Photon Detectors (SNSPDs) have become an integral part of quantum optics in recent years because of their high performance in single photon detection. We present a method to replace the electrical input by supplying the required bias current via the photocurrent of a photodiode situated on the cold stage of the cryostat. Light is guided to the bias photodiode through an optical fiber, which enables a lower thermal conduction and galvanic isolation between room temperature and the cold stage. We show that an off-the-shelf InGaAs–InP photodiode exhibits a responsivity of at least 0.55 A/W at 0.8 K. Using this device to bias an SNSPD, we characterize the count rate dependent on the optical power incident on the photodiode. This configuration of the SNSPD and photodiode shows an expected plateau in the single photon count rate with an optical bias power on the photodiode above 6.8 µW. Furthermore, we compare the same detector under both optical and electrical bias, and show there is no significant changes in performance. This has the advantage of avoiding an electrical input cable, which reduces the latent heat load by a factor of 100 and, in principle, allows for low loss RF current supply at the cold stage.
Today Superconducting Nanowire Single-Photon Detectors (SNSPDs) are commonly used in different photon-starved applications, including testing and diagnostics of VLSI circuits. Detecting very faint signals in the near-infrared wavelength range requires not only good detection efficiency, but also very low Dark Count Rate (DCR) and jitter. For example, low noise is crucial to enable ultra-low voltage optical testing of integrated circuits. The effect of detector temperature and background thermal radiation on the noise of superconducting single-photon detectors made of NbN meanders is studied in this paper. It is shown that two different regimes can be identified in the DCR vs. bias current characteristics. At high bias, the dark count rate is dominated by the intrinsic noise of the detector, while at low bias current it is dominated by the detection of stray photons that get onto the SNSPD. Changing the detector temperature changes its switching current and only affects the high bias branch of the characteristics: a reduction of the DCR can be achieved by lowering the SNSPD base temperature. On the other hand, changing the temperature of the single-photon light source (e.g. the VLSI circuit under test) only affects the low bias regime: a lower target temperature leads to a smaller DCR.
Superconducting nanowire single-photon detectors (SNSPDs) are integral to the fields of quantum information and quantum communication, offering high efficiency, low dark count rate, high count rate, and minimal timing jitter. However, a common challenge with SNSPDs is their propensity for latching and nonlinear count rate increase under high incident photon fluxes due to the traditional external readout circuitry. This issue is primarily caused by large dynamic inductance and the ac-coupled effects of the bias and amplifier capacitors. In this study, we carefully selected a commercial SNSPD with an efficiency of over 95%. To address the aforementioned challenges, we implemented a resistor–inductor-type filter structure, which is directly coupled to a low-temperature amplifier, and their operating temperature is 40 K. Experimental results revealed that the enhanced SNSPD readout circuit achieves a count rate that is approximately 3.5 times greater than that of the traditional circuit. Moreover, the timing jitter of the SNSPD was optimized, decreasing by approximately 3.6 times under high incident photon fluxes. These performance enhancements could significantly improve high-speed optical communication and quantum precision measurement.
Single-photon sources and detectors are key enabling technologies for photonics in quantum information science and technology (QIST). QIST applications place high-level demands on the performance of sources and detectors; it is therefore essential that their properties can be characterized accurately. Superconducting nanowire single-photon detectors (SNSPDs) have spectral sensitivity from visible to beyond 2 μm in wavelength, picosecond timing resolution (Jitter <100 ps FWHM) and the capacity to operate ungated with low dark counts (<1 kHz). This facilitates data acquisition at high rates with an excellent signal-to-noise ratio. We report on the construction and characterization of a two-channel SNSPD system. The detectors are mounted in a closed-cycle refrigerator, which eliminates reliance on liquid cryogens. Our specification was to deliver a system with 1% efficiency in both channels at a wavelength of 1310 nm with 1 kHz dark count rate. A full width at half maximum timing jitter of less than 90 ps is achieved in both channels. The system will be used to detect individual photons generated by quantum-optical sources at telecom wavelengths. Examples include single-photon sources based on quantum dots (emitting at 1310 nm). The SNSPD system's spectral sensitivity and timing resolution make it suited to characterization of such sources, and to wider QIST applications.
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Superconducting devices offer the potential to perform at speeds and detection efficiencies higher than what is possible using conventional technologies (such as semiconducting avalanche photodiodes and photomultiplier tubs) for wavelengths from the ultraviolet to the mid-infrared. As a result, there has been increasing interest in using superconducting optical photon detectors in a variety of applications. There has been significant progress in using these types of detectors in areas of basic research such as quantum information science and quantum optics. These applications require detectors that have extremely low dark count rates, high count rates, and high quantum efficiency. I will begin by describing some of our earlier work on superconducting Transition-Edge Sensor (TES). In particular, I will describe some of the engineering involved in the cryogenic, electrical, and optical packaging so that these devices can be easily coupled into fiber-based optics. I will also describe our recent work on developing superconducting nanowire single photon detectors (SNSPD or SSPD). An SNSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When one or more photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. At NIST and JPL, we have been developing nanowire detectors using an amorphous alloy of tungsten-silicide. We will describe to construct systems using tungsten-silicide nanowires to achieve high detection efficiency (>90% at 1550nm). I will also describe our work to improve the performance of the device by fabricating multiple nanowires in an electrically parallel structure to implement a superconducting nanowire avalanche photodiode (SNAP)[1]. One example of this type of detector is shown in Fig 1. In this case, there are two tungsten silicide layers separated by a dielectric layer to optimize detection of light for any polarization[2]. In addition, progress on other types of SNAP detectors will be described to increase the signal size from a single photon, reduce the recovery time of the device, and to improve the jitter.