We demonstrate a GHz-gated operation of superconducting nanowire single-photon detectors suitable for synchronous applications. In comparison with conventional dc-biased nanowire detectors, this method prevents the detector from latching and can suppress dark counts and background noise. Using a gating frequency of 3.8 GHz and a fast, synchronized laser diode, we show that the detector's operation point follows the oscillating current and its detection efficiency depends on the relative frequency and phase of the bias and modulated optical signal. The obtained experimental results are in good agreement with simulations, showing that the duty cycle of a gated detector can be adjusted in a wide range in case of a pronounced saturation of the current-dependent detection efficiency. This operation mode could be suitable for applications such as quantum key distribution and time-of-flight laser ranging.
We demonstrate a GHz-gated operation of superconducting nanowire single-photon detectors suitable for synchronous applications. In comparison with conventional dc-biased nanowire detectors, this method prevents the detector from latching and can suppress dark counts and background noise. Using a gating frequency of 3.8 GHz and a fast, synchronized laser diode, we show that the detector's operation point follows the oscillating current and its detection efficiency depends on the relative frequency and phase of the bias and modulated optical signal. The obtained experimental results are in good agreement with simulations, showing that the duty cycle of a gated detector can be adjusted in a wide range in case of a pronounced saturation of the current-dependent detection efficiency. This operation mode could be suitable for applications such as quantum key distribution and time-of-flight laser ranging.
We demonstrate a GHz-gated operation of resonator-coupled superconducting nanowire single-photon detectors suitable for synchronous applications. In comparison with conventional dc-biased nanowire detectors, this method prevents the detector from latching and can suppress dark counts and background noise. Using a gating frequency of 3.8 GHz and a fast, synchronized laser diode, we show that the detector's operation point follows the oscillating current and its detection efficiency depends on the relative frequency and phase of the bias and modulated optical signal. The obtained experimental results are in good agreement with simulations, showing that the duty cycle of a gated detector can be adjusted in a wide range in the case of a pronounced saturation of the current-dependent detection efficiency. This operation mode could be suitable for applications such as quantum key distribution and time-of-flight laser ranging.
This paper presents a detailed investigation of superconducting nanowire single-photon detectors biased with microwave and direct currents. We developed a hybrid detector, which allows the operation in the RF and dc operation mode. With this hybrid detector, we are able to compare the count rates of the same nanowire biased with dc and RF currents. Furthermore, we demonstrate the use of the oscillating current in the RF operation mode as a reference signal in a synchronous single-photon detection mode.
Superconducting nanowire single-photon detectors (SNSPDs) are attractive because of their wide response band, low noise, and high repetition rate in practical applications. Owing to these advantage, SNSPDs are particularly useful for high efficiency (>80%) in laser-ranging systems operating at 1064 nm. However, the superconducting nanowire may latch in a permanent resistive state because of the backscattering problem, which may prevent it from detecting targeted reflection photons. This paper proposes an SNSPD that operates in a quasi-gated mode with the help of a programmed source and improved feeding circuit. The programmed source switches the SNSPD off at a low level, and switches it on at a high level. Such an on-off switching process enables the SNSPD to recover automatically from latching through compulsory initialization in each period, therefore, resolving the problem caused by strong backscatterings in laser ranging systems. The quasi-gated SNSPD can also be used in other applications operating in a nonstop mode, even with occasional latchings.
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.
Superconducting nanowire single photon detector (SNSPD) has been widely used in many fields such as quantum computing, quantum key distribution and laser radar, due to its high detection efficiency, low dark count rate, high counting rate, and low timing jitter. In most cases, the SNSPD works under the DC-bias mode that can detect single photons arrived at any time. In some cases such as satellite laser ranging and single-photon laser radar where the light pulses arrive regularly, the AC-bias mode enables the SNSPD to work with higher counting rates and lower background dark counts, which however requires complicated readout due to the low signal-to-noise ratio of the photon response. In this work, we report on an AC-biased SNSPD system with a self-differential readout circuit. The system includes a 2-pixel SNSPD consisting of two parallel nanowires, which are biased with 100 MHz sinusoidal current. The output signals of these two nanowires are amplified and combined for the differential readout of the photon response. The resulting response pulse possesses a signal-to-noise ratio ten times higher than that extracted before self-differential readout. In addition, the dark counts are reduced by a factor of 4, and the count rates are increased by a factor of 1.5, in comparison with those under the DC-bias mode. This work provides a specific method to read out the AC-biased SNSPD.