Abstract Count rate (CR) is one of the key parameters of superconducting nanowire single-photon detectors (SNSPDs). The practical SNSPDs usually have a CR of a few MHz to a few tens of MHz owing to the large kinetic inductance originating from the long nanowire, which is necessary for effectively coupling the photons. A feasible approach to decrease the kinetic inductance and consequently increase the detection speed is to replace a long single nanowire with multiple individual nanowires in an array. In this study, we report an SNSPD of nine interleaved nanowires with 70% system detection efficiency (SDE) and 200 Hz dark count rate at the low-photon-flux limit of 1550 nm. Owing to the small dead time (<6 ns) of each nanowire, the SNSPD achieved a maximum CR of 0.93 GHz at a photon flux of 1.26 × 10 10 photons s −1 with an SDE of ∼7.4%, and a CR of 200 MHz with an SDE of over 50%. Furthermore, a photon number resolvability of up to nine photons was also demonstrated.
Abstract Count rate (CR) is one of the key parameters of superconducting nanowire single-photon detectors (SNSPDs). The practical SNSPDs usually have a CR of a few MHz to a few tens of MHz owing to the large kinetic inductance originating from the long nanowire, which is necessary for effectively coupling the photons. A feasible approach to decrease the kinetic inductance and consequently increase the detection speed is to replace a long single nanowire with multiple individual nanowires in an array. In this study, we report an SNSPD of nine interleaved nanowires with 70% system detection efficiency (SDE) and 200 Hz dark count rate at the low-photon-flux limit of 1550 nm. Owing to the small dead time (<6 ns) of each nanowire, the SNSPD achieved a maximum CR of 0.93 GHz at a photon flux of 1.26 × 10 10 photons s −1 with an SDE of ∼7.4%, and a CR of 200 MHz with an SDE of over 50%. Furthermore, a photon number resolvability of up to nine photons was also demonstrated.
Increasing the count rate (CR) is one of the key issues in the development of superconducting nanowire single-photon detectors (SNSPDs) for different applications. This study aims to design, fabricate, and analyze a 16-pixel interleaved nanowire SNSPD array, which exhibits a system detection efficiency (SDE) of 72% and a dark CR of 100 Hz at a low-photon-flux limit and a wavelength of 1550 nm. By exploiting the increased pixel number and reduced dead time (10photons/s. Moreover, the SNSPD achieved a photon number resolution of up to 16 photons.
Abstract A series superconducting nanowire single-photon detector is a high performance nanowire array detector that has the potential to reach a high system detection efficiency (SQE), a high counting rate (CR) and photon number resolving functionality. Interconnected with a simplified readout, it shows promise for large scale expansion and has good prospects for future applications in single-photon imaging, quantum optics, quantum computing and deep-space communication. In this paper, we demonstrate a high SQE and CR series superconducting nanowire single-photon detector with an active area of 20 × 20 μ m 2 . The detector shows a maximum SQE of 68% at 1550 nm with a dark count rate of 200 Hz and a wide response wavelength from 1100–2000 nm. It also achieves a CR over 300 MHz at single photon power level and has the capability of resolving photon numbers by up to six photons.
Ever since superconducting nanowire single-photon detectors (SNSPDs or SSPDs) were demonstrated, they have attracted a considerable attention due to the detectors’ promising performance that includes high detection efficiency (DE), low dark count rate (DCR), broadband sensitivity, and low timing jitter. The system detection efficiency (SDE) has been improved to be over 90% with a wavelength of 1550 nm in a fiber-coupled system by embedding the SNSPD in optical cavities. However, the implementation of optical cavity usually reduces the bandwidth of SNSPDs. As a result, there are some recent works on increasing the bandwidth of SNSPD. Furthermore, the size of the active area of meandered nanowires has to be compatible with the core size of an optical fiber such that good optical coupling can be achieved; this setup requires a long nanowire with a large kinetic inductance, thus resulting in a small counting rate and a large timing jitter, particularly for multi-mode fiber-coupled devices. Nevertheless, a particularly impressive waveguide-coupled SNSPD has been developed in recent years. By placing an SNSPD atop an optical waveguide that has been fabricated on various substrate materials, photons propagating in the waveguide have been found to be evanescently absorbed by nanowires that are only a few tens of microns long. The on-chip DE of this device has been estimated to be over 90%, thus indicating that it has both high absorptance and high intrinsic DE. If the waveguide and the nanowire are correctly dimensioned, the absorptance of this device can reach over 90% for a wavelength range of more than 700 nm. Furthermore, the length of the nanowire is shorter than that of the fiber-coupled SNSPD, thus leading to a higher count rate and lower timing jitter (~18 ps). However, unsatisfactory coupling losses between the optical fiber and the waveguide in such devices can decrease its SDE (~10%), thus limiting its applicability to quantum photonic integrated circuits (QPIC). Recently, we proposed a type of SNSPD that was coupled with microfibers (MFs), and simulations for this SNSPD indicated that its absorption would be as high as 90%. Microfibers and nanofibers, tapered adiabatically from standard fibers, with diameters close to or smaller than the wavelength of the guided light were demonstrated to have low transmittance losses by Tong et al. in 2003. MFs have been shown to have many interesting properties, such as strong evanescent fields, tight optical confinement, wideband abilities, and small masses; these properties are appealing for applications such as optical sensing and coupling. MFs also provide seamless connections with high transmittance from standard fibers; therefore, MF-coupled SNSPDs can achieve both high SDEs and wideband compatibility. We proposed and demonstrated the MF-coupled SNSPDs successfully. The simulation results indicate that with optimal device structure, the optical absorption with efficiency < 90% can be realized over a wavelength range of 350 nm to 2150 nm. The fabricated MF-coupled SNSPD, shows unparalleled broadband system detection efficiencies (SDEs) of more than 50% from 630 nm to 1500 nm. The SDEs reach 66% at 785 nm and 45% at 1550 nm. These results pave the way for ultra-broadband weak light detection with quantum-limit sensitivity.
Superconducting series nanowire single-photon detectors (SNDs) have been used for resolving photon numbers. But it can also exhibit a higher counting rate than a single superconducting nanowire single-photon detector (SNSPD), because the serial architecture allows multiple detectors working in parallel and the inductance of each pixel is reduced. In this paper, we found each pixel of the SND could reset fast although the whole detector took a much longer time for recovering. Therefore, the speed of an SND with a large kinetic inductance of 1.25 μH was characterized and compared to a standard SNSPD with the same total inductance. By measuring the detected photon rate over the input photon rate, we obtained a photon counting rate enhancement by 7.5 times. Meanwhile, the timing jitter of the SND was 63 ps at single photon detection regime. Our results show that the series structure and the readout scheme are quite practical in realizing high speed single-photon detectors besides resolving photon numbers.
Superconducting nanowire single-photon detectors (SNSPDs) with both an ultra-large-active area and a high count rate (CR) are challenging from the design and fabrication. Here, we develop a NbN SNSPD with a circular active area of 300 μm-in-diameter and use multiple approaches to boost the maximal count rate (MCR). This large-active-area SNSPD is divided into nine pixels (parts). Each pixel consists of serially connected two superconducting nanowire avalanche photodetectors (SC-2SNAP), which yielded a four-fold reduction in the kinetic inductance of a single pixel. To further increase MCR, an optimized series resistance of about 380 Ω is added to each pixel, reducing the full recovery time of each pixel from a few microseconds to approximately 90 ns. All nine pixels show uniform superconducting critical temperatures of ∼7.4 K and switching currents in the range of 15.3–16.7 μA. When the detector coupled to a single-mode fiber and illuminated with 1064-nm photons, the single-pixel exhibits a well-saturated system detection efficiency (SDE) of 67% at a dark CR of 30 Hz, and its CR exceeds 10 MHz with an SDE of 50%. When coupled to a 200-μm multi-mode fiber, the total SDE of nine pixels is approximately 42% and the total MCR exceeds 43 MHz.
Superconducting nanowire single-photon detectors (SNSPDs) have enabled the realization of several quantum optics technologies thanks to their high system detection efficiency (SDE), low dark counts, and fast recovery time. However, the widespread use of linear optical quantum computing, quasi-deterministic single-photon sources, and quantum repeaters requires even faster detectors that can also distinguish between different photon-number states. Here, we present an SNSPD array composed of 14 independent pixels, achieving an SDE of 90% in the telecommunications band. By reading each pixel of the array independently, we show detection of telecommunication photons at 1.5 GHz with 45% absolute SDE. We exploit the dynamic photon-number resolution of the array to demonstrate accurate state reconstruction for a wide range of light inputs, including operation with long-duration light pulses, as obtained with some cavity-based sources. We show two-photon and three-photon fidelities of 74% and 57%, respectively, which represent state-of-the-art results for fiber-coupled SNSPDs.