Superconducting nanowire single photon detector (SNSPD) plays a significant role in plenty of fields such as quantum information, deep space laser communication and lidar, while the mechanism of the photon response process still lacks a recognized theory. It is prerequisite and essential for fabricating high-performance SNSPD to understand in depth and clarify the photon response mechanism of the SNSPD. As mature theories on the SNSPD response progress, hot-spot model and vortex-based model both have their disadvantages: in the former there exists the cut-off wavelength and in the later there is the size effect, so they both need further improving. The Cut-off wavelength means that the detection efficiency of the SNSPD drops to zero with the increase of light wavelength, which is indicated by the hot-spot model but not yet observed in experiment. The size effect implies that the vortex does not exist in the weak link with the width less than 4.41ξ, where ξ is the GL coherence length. Phase slip is responsible for the intrinsic dissipation of superconductors, which promises to expound the SNSPD photon response progress and to establish a complete theory. This paper reviews and discusses the fundamental conception, the development history and the research progress of the hot-spot models, i.e. the vortex-based model and the superconductor phase slips, providing a reference for studying the SNSPD photon response mechanism.
Superconducting nanowire single photon detector (SNSPD) plays a significant role in plenty of fields such as quantum information, deep space laser communication and lidar, while the mechanism of the photon response process still lacks a recognized theory. It is prerequisite and essential for fabricating high-performance SNSPD to understand in depth and clarify the photon response mechanism of the SNSPD. As mature theories on the SNSPD response progress, hot-spot model and vortex-based model both have their disadvantages: in the former there exists the cut-off wavelength and in the later there is the size effect, so they both need further improving. The Cut-off wavelength means that the detection efficiency of the SNSPD drops to zero with the increase of light wavelength, which is indicated by the hot-spot model but not yet observed in experiment. The size effect implies that the vortex does not exist in the weak link with the width less than 4.41ξ, where ξ is the GL coherence length. Phase slip is responsible for the intrinsic dissipation of superconductors, which promises to expound the SNSPD photon response progress and to establish a complete theory. This paper reviews and discusses the fundamental conception, the development history and the research progress of the hot-spot models, i.e. the vortex-based model and the superconductor phase slips, providing a reference for studying the SNSPD photon response mechanism.
The superconducting nanowire single photon detector (SNSPD) is currently one of the best detectors with comprehensive performance in the mid-infrared wavelength, which has been widely used in quantum optics, LiDAR, and biological fluorescence detection. To develop new devices with excellent performance, the photon detection mechanism of SNSPD still needs further research. Here we find that the single quantum phase slip is the dominating mechanism leading to dark-count and photon-response events in SNSPD below the quantum temperature. We fabricate the nanowire with a length of 7.5 μm and a width of 25 nm using niobium nitride film with a thickness of 5 nm. The distribution of the superconducting switching current is measured as a function of temperature at temperatures ranging from 0.3 to 7 K. We observe single quantum phase slips in the nanowire at the temperature below 1.2 K, and we further investigate the quantitative relationship between the single quantum phase slip rate and the superconducting switching rate of the nanowire under the laser illumination. Experimental results show that the single quantum phase slip is a significant factor leading to photon response and dark counts in the nanowire below the quantum temperature. Our research helps to further reveal the photon detection mechanism of the SNSPD, laying a theoretical foundation for the development of high-performance SNSPD.
Abstract Superconducting nanowire single-photon detectors (SNSPDs) have been widely applied in quantum information and deep-space exploration owing to their high detection efficiency, low dark count rate, and wide spectral response. In particular, the heat transfer in SNSPDs largely affects their performance parameters (e.g. quantum efficiency, count rates and recovery time), which can be modulated to optimize the performance and develop novel devices. Considering the potential of SNSPDs and the significance of heat transfer, the most recent progress toward understanding the mechanism and the modulation of heat transfer in SNSPDs is critically reviewed, with particular emphasis on the macroscopic correlation with device performance parameters and the microscopic analysis of existing theories, especially at interfaces. Furthermore, representative novel devices inspired by the need for heat transfer modulation in SNSPDs are discussed in detail. Finally, the development of heat transfer in SNSPDs is placed in perspective with the aim of highlighting future theoretical directions and practical applications.
Photon detectors connect optical and electrical systems by converting light to electrical signals. Single photon detectors detect single photons which measure ultra-weak light. Traditional semiconductor single-photon detectors suffer from high dark count rates, low infrared detection efficiency, and poor temporal resolution. Superconducting-nanowire single-photon detectors (SNSPDs) overcome these limitations using the hotspot effect. SNSPDs have created a solid foundation for optical technologies and become key in quantum information, LiDARs and Deep-Space Communications. This paper reviews working principles and performance metrics: system detection efficiency, dark count rate, recovery time, and timing jitter. The study summarizes applications in quantum information (quantum key distribution, optical quantum computing), single-photon LiDAR, and deep-space optical communication, replacing most single-photon avalanche diodes (SPADs). Recent experiments show that SNSPD-based systems can achieve meter-scale detection of sea fog, interplanetary laser communication over billions of kilometers, and boson sampling with 20 photons. Ongoing research is expected to improve performance in maximum count rate, system integration, and cryogenic operation, as well as to find applications in emerging fields such as environmental monitoring.
Superconducting nanowire single photon detector (SNSPD) is a leading candidate for applications requiring the fundamental limit of light detection at high detection rates. While SNSPD technology employing nanowires from conventional low temperature superconducting detectors is mature with several commercial solutions, other material options with higher transition temperature approaching liquid nitrogen with faster signal responses are actively being explored. In this context, we develop a comprehensive model that predicts the final potential response from an SNSPD incorporating several physical and material aspects. A phase diagram of photon detection is developed that describes the latching phases and the photon sensitivity as a function of biasing current and temperature for both low temperature and high temperature superconductors. On the one hand, while low temperature superconductors are observed to be more sensitive than high temperature superconductors (HTSs) under any given biasing condition, a biasing window for a single photon detection with HTS nanowires is identified. On the other hand, HTS nanowires demonstrate three orders of magnitude faster response times than the low temperature superconductor nanowire at the same biasing condition, making it uniquely suited for several practical applications.
Superconducting nanowire single photon detector (SNSPD) is an optical detector with quantum-limit sensitivity. The detection mechanism is based on the Cooper-pair breaking by the photon energy, which results in a phase transition from superconducting state to non-superconducting state. SNSPDs surpass the semiconducting counterparts with high detection efficiency, low dark count rate, small timing jitter, short dead time, broad spectrum sensitivity as well as free-running etc. SNSPDs with high performance have been applied in various fields, such as, quantum information, laser communication, light detection and ranging. The progress of SNSPD research and development, application as well as commercialization at home and abroad in the past few years was summarized. An outlook of SNSPDs' RD as well as applications was also provided.
Superconducting microstrips single-photon detectors (SMSPDs) are a novel type of single-photon sensor based on superconducting thin films patterned into micrometer-scale strip widths. Compared with superconducting nanowire single-photon detectors (SNSPDs), SMSPDs not only substantially lower the fabrication dependence on high-precision electron-beam lithography, but also exhibit lower kinetic inductance, higher bias current, and weaker polarization sensitivity. These advantages pave a new route toward superconducting single-photon detection systems with large active areas and low dark-count rates. Because of their performance, SMSPDs exhibit tremendous application potential in cutting-edge fields such as quantum communication, LiDAR, dark-matter searches, and high-energy particle detection. Accordingly, this paper provides a systematic review of recent advances in SMSPD research, covering the underlying physical mechanisms, material systems, geometrical design, readout circuitry, and application domains. Firstly, this review elaborates on the photon response mechanism of SMSPDs and clarifies its correlation with vortex dynamics. Secondly, this review categorizes the superconducting materials used for SMSPD fabrication and analyzes the influences of characteristic thin-film parameters on device performance. Furthermore, this work concludes the evolution and optimization strategies of geometrical design and readout circuit schemes for SMSPDs, and presents the current application status. Finally, we offer perspectives on its future development trajectory. This review provides a foundation in physical mechanisms and design guidance for the development of large active area SMSPDs with high efficiency and low dark counts.