Local detection efficiency of a NbN superconducting single photon detector explored by a scattering scanning near-field optical microscope

Wang, Qiang; Renema, Jelmer J.; Engel, A.; Exter, M. P. van; Dood, M. J. A. de

doi:10.1364/oe.23.024873

Cited by 7 publications

(7 citation statements)

References 33 publications

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“…The effects of geometry on timing jitter became clearer when devices that involve SNSPDs connected in parallel (superconducting nanowire avalanche photodetectors, SNAPs) and other large‐area devices demonstrated high SNR but high timing jitter . Similar to DE and DCR, constrictions in the wires (narrower areas due to inhomogeneity in fabrication, due to substrates effects, due to granular structure or due to current crowding) deteriorate also timing performance . Pictorial illustration of the effects of constrictions and inhomogeneities on timing jitter is given in Figure .…”

Section: Intrinsic Properties and Functionalitymentioning

confidence: 99%

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Superconducting Nanowires for Single‐Photon Detection: Progress, Challenges, and Opportunities

2019

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Single-photon detectors and nanoscale superconducting devices are two major candidates for realizing quantum technologies. Superconducting-nanowire single-photon detectors (SNSPDs) comprise these two solid-state and optic aspects enabling high-rate (1.3 Gb s −1 ) quantum key distribution over long distances (>400 km), long-range quantum communication (>1200 km), as well as space communication (239 000 miles). The attractiveness of SNSPDs stems from competitive performance in the four single-photon relevant characteristics at wavelengths ranges from UV to the mid-IR: high detection efficiency, low false-signal rate, low uncertainty in photon time arrival, and fast reset time. However, to date, these characteristics cannot be optimized simultaneously. In this review, the mechanisms that govern these four characteristics are presented, and it is demonstrated how they are affected by material properties and device design as well as by the operating conditions, allowing aware optimization of SNSPDs. Based on the evolution in the existing literature and state of the art, it is proposed how to choose or design the material and device for optimizing SNSPD performance, while possible future opportunities in the SNSPD technology are also highlighted.

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Section: Intrinsic Properties and Functionalitymentioning

confidence: 99%

“…The dimensions of the wires also have a strong effect on the timing jitter. Longer and narrower wires comprise higher probability for inhomogeneities and constrictions . These dimensions affect also the timing jitter more directly.…”

Section: Intrinsic Properties and Functionalitymentioning

confidence: 99%

Superconducting Nanowires for Single‐Photon Detection: Progress, Challenges, and Opportunities

2019

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“…In addition to characterizing the properties of the near-field interaction, the ability to directly probe evanescent fields, without the need to scatter the evanescent field into propagating radiation, is a promising approach for improving the sensitivity of SNOM and for expanding the applications of this technique to new areas. The presented work is a step towards developing a nanoscale single-photon detector integrated onto a scanning tip [14][15][16] .…”

Section: Motivationmentioning

confidence: 99%

Position-Dependent Local Detection Efficiency in a Nanowire Superconducting Single-Photon Detector

et al. 2015

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We probe the local detection efficiency in a nanowire superconducting single-photon detector along the cross-section of the wire with a spatial resolution of 10 nm. We experimentally find a strong variation in the local detection efficiency of the device. We demonstrate that this effect explains previously observed variations in NbN detector efficiency as function of device geometry.Nanowire superconducting single-photon detectors (SSPDs) consist of a superconducting wire of nanoscale cross-section [1], typically 4 nm by 100 nm. Photon detection occurs when a single quantum of light is absorbed and triggers a transition from the superconducting to the normal state. SSPDs have high efficiency, low jitter, low dark count rate and fast reset time [2], and are therefore a key technology for, among others, quantum key distribution Although progress has been made recently, the underlying physical mechanism responsible for photon detection on the nanoscale is still under active investigation. A combination of theory [6,7], experiments [8][9][10] and simulations [11,12] on NbN SSPDs indicates that the absorption of a photon destroys Cooper pairs in the superconductor and creates a localized cloud of quasiparticles that diverts current across the wire. This makes the wire susceptible to the entry of a superconducting vortex from the edge of the wire. Energy dissipation by this moving vortex drives the system to the normal state.An important and unexpected implication of this detection model is a nanoscale position variation in the photodetection properties of the device. The conditions at the entry point of the vortex determine the energy required for it to cross the wire. This causes photons absorbed close to the edge to have a local detection efficiency (LDE) [13] compared to photons absorbed in the center of the wire [12]. This effect has practical implications for the operation of SSPDs, since it represents a potential limitation of the detection efficiency. In addition, SSPDs have been proposed for nanoscale sensing, either in a near-field optical microscope configuration [14] or as a subwavelength multiphoton probe [15], where this effect would be of major importance for the properties of such a microscope. While this effect has been predicted theoretically, clear experimental evidence is missing. * renema@physics.leidenuniv.nlIn this work, we experimentally explore the nanoscale variations in the intrinsic response of the detector. We spatially resolve the LDE with a resolution of approximately 10 nm, better than λ/50, using far-field illumination only. We find that our results are qualitatively consistent with numerical simulations [11,12]. Our results provide excellent quantitative agreement with experiments that indicate a polarization dependence in the LDE that was hitherto not understood [16].The key technique used in this work is a differential polarization measurement that probes the IDE of the detector (see Figure 1). The technique is based on the fact that polarized light is absorbed preferentially in dif...

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“…Calculations for the 1000-nm wavelength show that the enhancement is a broadband effect. More-complex designs, not necessarily limited to the use of dielectrics, can be envisaged that enhance device performance further or that resonantly enhance the IDE for a particular wavelength or wavelength range [40].…”

Section: Discussionmentioning

confidence: 99%

Design of NbN Superconducting Nanowire Single-Photon Detectors with Enhanced Infrared Detection Efficiency

et al. 2017

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We optimize the design of NbN nanowire superconducting single-photon detectors using the recently discovered position-dependent detection efficiency in these devices. This optimized design of meandering wire NbN detectors maximizes absorption at positions where photon detection is most efficient by altering the field distribution across the wire. In order to calculate the response of the detectors with different geometries, we use a monotonic local detection efficiency from a nanowire and optical absorption distribution via finite-difference-time-domain simulations. The calculations predict a trade-off between average absorption and absorption at the edge, leading to a predicted optimal wire width close to 100 nm for a 1550-nm wavelength, which drops to a 50-nm wire width for a 600-nm wavelength. The absorption at the edges can be enhanced by depositing a silicon nanowire on top of the superconducting nanowire, which improves both the total absorption efficiency and the internal detection efficiency of meandering wire structures. The proposed structure can be integrated in a relatively simple cavity structure to reach absorption efficiencies of 97% for perpendicular and 85% for parallel polarization.

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Local detection efficiency of a NbN superconducting single photon detector explored by a scattering scanning near-field optical microscope

Cited by 7 publications

References 33 publications

Superconducting Nanowires for Single‐Photon Detection: Progress, Challenges, and Opportunities

Superconducting Nanowires for Single‐Photon Detection: Progress, Challenges, and Opportunities

Position-Dependent Local Detection Efficiency in a Nanowire Superconducting Single-Photon Detector

Design of NbN Superconducting Nanowire Single-Photon Detectors with Enhanced Infrared Detection Efficiency

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