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Quantum Sensing and Nano Electronics and Photonics

Fast time-gated superconducting nanowire single-photon detectors

Antonio Guardiani, Lieuwe Locht, Martín Caldarola, Andreas Fognini, Sinda Meijri

Published Mar 21, 2025• 0 citations
Publisher

Abstract

Superconducting Nanowire Single-Photon Detectors (SNSPDs) are well known for their single-photon sensitivity, low jitter, and high efficiency. Their dynamic range is generally limited either to zero or one (no photon, or a photon absorbed), and if single-photon sensitivity is needed in the vicinity of a strong light pulse, a counteraction like gating needs to be deployed. In such a scheme, we aim at the fastest possible transition time which is helpful to increase sensitivity, to temporally filter any strong laser excitation, and further suppress dark counts. Here, we present our work of time-gated SNSPDs where the detection current can be switched on- and off to allow the detector not to be saturated. We start our discussion by introducing the simplest gating scheme based on a square wave resulting in switch-off-switching transition times of ≈50ns. Then we present a new method to improve this relatively slow transition time to the sub-nanosecond range. Latest measurements of efficiency recovery and jitter are presented, and we show that a 1550nm light pulse with 100’000 photons within 500ns, applied right before the on-transition of the SNSPD, does not yet affect the performance in the on-state.

DOI
10.1117/12.3057941

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Superconducting Nanowire Single-Photon Detectors (SNSPDs) are well known for their single-photon sensitivity, low jitter, and high efficiency. Their dynamic range is generally limited either to zero or one (no photon, or a photon absorbed), and if single-photon sensitivity is needed in the vicinity of a strong light pulse, a counteraction like gating needs to be deployed. In such a scheme, we aim at the fastest possible transition time which is helpful to increase sensitivity, to temporally filter any strong laser excitation, and further suppress dark counts. Here, we present our work of time-gated SNSPDs where the detection current can be switched on- and off to allow the detector not to be saturated. We start our discussion by introducing the simplest gating scheme based on a square wave resulting in switch-off-switching transition times of ≈50ns. Then we present a new method to improve this relatively slow transition time to the sub-nanosecond range. Latest measurements of efficiency recovery and jitter are presented, and we show that a 1550nm light pulse with 100’000 photons within 500ns, applied right before the on-transition of the SNSPD, does not yet affect the performance in the on-state.
Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.
In recent years, Superconducting Nanowire Single-Photon Detectors (SNSPDs) have obtained tremendous attention as a possible key technology for photonic quantum processing and faint light detection. Here, we present our recent progress on engineering of the properties of NbTiN SNSPDs fabricated on various substrates measured. We discuss approaches to simultaneously improve the most important figures of merit (DCR, dead time, timing jitter, efficiency) as well as efficient characterization methods. Specifically, for the latter we investigate the impact of the substrate material on the performance parameters as well as the fundamental interrelation of the resulting voltage pulse properties, such as pulse height, rise time and timing jitter, and their dependence on the applied bias current.
Detecting single photons is essential for applications such as dark matter detection, quantum science and technology, and biomedical imaging. Superconducting nanowire single-photon detectors (SNSPDs) excel in this task due to their near-unity detection efficiency, subhertz dark count rates, and picosecond timing jitter. However, a local increase of current density (current crowding) in the bends of meander-shaped SNSPDs limits these performance metrics. By locally irradiating the SNSPD’s straight segments with helium ions while leaving the bends unirradiated, we realize current crowding–free SNSPDs with simultaneously enhanced sensitivity: After irradiation with 800 ions nm −2 , locally irradiated SNSPDs showed a relative saturation plateau width of 37%, while fully irradiated SNSPDs reached only 10%. This larger relative plateau width allows operation at lower relative bias currents, thereby reducing the dark count rate while still detecting single photons efficiently. We achieve an internal detection efficiency of 94% with 7 mHz dark count rate near the onset of saturating detection efficiency for a wavelength of 780 nm.
Superconducting nanowire single photon detectors (SNSPDs) have demonstrated advantages over traditional detectors in many fields [1]. Most fiber-coupled SNSPDs are coupled to single mode fibers, limiting their usability for applications where large surface area detectors are needed, for example fluorescence detection and satellite-based quantum communication [2][3]. Other important requirements for many applications are broadband detection efficiency, and low timing jitter [4]. So far, the increased meander length of multimode detectors, and the therefore increased kinetic inductance and number of imperfections due to film inhomogeneities have limited the timing jitter [5]. Moreover, combining low timing jitter with high detection efficiency and low dark count rate in one device is challenging due to the tradeoffs between different properties of SNSPDs [6]. In this paper, we achieved high efficiency and strong saturation over a broad wavelength range with a low timing jitter of 16.99 ps while maintaining a low dark count rate of < 0.2 Hz for an SNSPD coupled to a 50 µm core multimode fiber. To enhance the broadband absorption from 405 nm to 830 nm, detectors were fabricated on an optimized SiO2 cavity and Aluminum mirror. The geometry of the nanowire was also tuned to reach a good internal saturation of efficiency over the visible/NIR range but also to carry high current to get a large signal. Furthermore, a cryogenic readout amplifier was optimized to improve the signal to noise ratio and thus lead to high time resolution. Our devices can be readily used to enable higher resolution and faster quantum optics, bio-imaging, laser ranging and other optical experiments.
Abstract Superconducting Nanowire Single-Photon Detectors (SNSPDs) are key building blocks for photonic quantum technologies due to their ability to detect single photons with ultra-high efficiency, low dark counts and fast temporal resolution. Superconducting materials exhibiting high uniformity, large absorption cross-section and atomic-scale thickness are desirable to extend single-photon detection from the near-infrared up to the terahertz regime, where existing material choices are especially constrained. Substrate independence would further open the way to integrating detectors onto functional materials and heterostructures, enhancing performance and enabling proximal readout of a wide range of individual excitations. Here, we pattern the prototypical two-dimensional superconductor niobium diselenide (NbSe 2 ) into few-layer nanowires less than 100 nm wide and demonstrate single-photon detection at 780 nm and 1550 nm. At the same time, the dark-count rate remains below 1 Hz up to the switching current and we achieve a timing jitter below 50 ps. We estimate via a diffusive hot-spot model that materials and geometric parameters would allow a theoretical cut-off wavelength in the millimetre range, assuming state-of-the-art device parameters. Our results open up routes toward quantum-limited detectors integrated into quantum-photonic circuits and quantum devices, with the potential for novel detection capabilities and unprecedented energy sensitivity.
High detection efficiency and low intrinsic dark count rate are two advantages of superconducting nanowire single photon detectors (SNSPDs). However, the stray photons penetrated into the fiber would cause the extrinsic dark count rate, owing to the free running mode of SNSPDs. In order to improve the performance of SNSPDs in realistic scenarios, stray photons should be investigated and suppression methods should be adopted. In this study, we demonstrate the pulse-gated mode, with 500 kHz gating frequency, of a commercial SNSPD system for suppressing the response of stray photons about three orders of magnitude than its free-running counterpart on the extreme test conditions. When we push the gating frequency to 8 MHz, the dark count rate still keeps under 4% of free-running mode. In experiments, the intrinsic dark count rate is also suppressed to 4.56 × 10−2 counts per second with system detection efficiency of 76.4372%. Furthermore, the time-correlated single-photon counting analysis also approves the validity of our mode in suppressing the responses of stray photons.