Zolotov, P., Divochiy, A., Vakhtomin, Y., Moshkova, M., Morozov, P., Seleznev, V., et al. (2018). Photon-number-resolving SSPDs with system detection efficiency over 50% at telecom range. In Proc. AIP Conf. (Vol. 1936, 020019).
Abstract: We used technology of making high-efficiency superconducting single-photon detectors as a basis for improvement of photon-number-resolving devices. By adding optical cavity and using an improved NbN superconducting film, we enhanced previously reported system detection efficiency at telecom range for such detectors. Our results show that implementation of optical cavity helps to develop four-section device with quantum efficiency over 50% at 1.55 µm. Performed experimental studies of detecting multi-photon optical pulses showed irregularities over defining multi-photon through single-photon quantum efficiency.
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Baeva, E., Sidorova, M., Korneev, A., & Goltsman, G. (2018). Precise measurement of the thermal conductivity of superconductor. In Proc. AIP Conf. (Vol. 1936, 020003 (1 to 4)).
Abstract: Measuring the thermal properties such as the heat capacity provide information about intrinsic mechanisms operated inside. In general, the ratio between electron and phonon specific heat Ce/Cp shows how the absorbed energy shared between electron and phonon subsystems. In this work we make estimations for amplitude-modulated absorption of THz radiation technique for investigation of the ratio Ce/Cp in superconducting Niobium Nitride (NbN) at T = Tc. Our results indicates that experimentally the frequency of modulation has to be extra large to extract the quantity. We perform a new technique allowed to work at low frequency with accurately measurement of absorbed power.
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Milostnaya, I., Korneev, A., Tarkhov, M., Divochiy, A., Minaeva, O., Seleznev, V., et al. (2008). Superconducting single photon nanowire detectors development for IR and THz applications. J. Low Temp. Phys., 151(1-2), 591–596.
Abstract: We present our progress in the development of superconducting single-photon detectors (SSPDs) based on meander-shaped nanowires made from few-nm-thick superconducting films. The SSPDs are operated at a temperature of 2–4.2 K (well below T c ) being biased with a current very close to the nanowire critical current at the operation temperature. To date, the material of choice for SSPDs is niobium nitride (NbN). Developed NbN SSPDs are capable of single photon counting in the range from VIS to mid-IR (up to 6 μm) with a record low dark counts rate and record-high counting rate. The use of a material with a low transition temperature should shift the detectors sensitivity towards longer wavelengths. We present state-of-the art NbN SSPDs as well as the results of our recent approach to expand the developed SSPD technology by the use of superconducting materials with lower T c , such as molybdenum rhenium (MoRe). MoRe SSPDs first were made and tested; a single photon response was obtained.
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Goltsman, G., Korneev, A., Izbenko, V., Smirnov, K., Kouminov, P., Voronov, B., et al. (2004). Nano-structured superconducting single-photon detectors. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 520(1-3), 527–529.
Abstract: NbN detectors, formed into meander-type, 10×10-μm2 area structures, based on ultrathin (down to 3.5-nm thickness) and nanometer-width (down to below 100 nm) NbN films are capable of efficiently detecting and counting single photons from the ultraviolet to near-infrared optical wavelength range. Our best devices exhibit QE >15% in the visible range and ∼10% in the 1.3–1.5-μm infrared telecommunication window. The noise equivalent power (NEP) ranges from ∼10−17 W/Hz1/2 at 1.5 μm radiation to ∼10−19 W/Hz1/2 at 0.56 μm, and the dark counts are over two orders of magnitude lower than in any semiconducting competitors. The intrinsic response time is estimated to be <30 ps. Such ultrafast detector response enables a very high, GHz-rate real-time counting of single photons. Already established applications of NbN photon counters are non-invasive testing and debugging of VLSI Si CMOS circuits and quantum communications.
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Манова, Н. Н., Корнеева, Ю. П., Корнеев, А. А., Слыш, В., Воронов, Б. М., & Гольцман, Г. Н. (2011). Сверхпроводниковый NbN однофотонный детектор, интегрированный с четвертьволновым резонатором. ПЖТФ, 37(10), 7.
Abstract: Исследована спектральная зависимость квантовой эффективности сверхпроводниковых NbN однофотонных детекторов, интегрированных с оптическими четвертьволновыми резонаторами с использованием диэлектриков Si3N4, SiO2, SiO.
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Kerman, A. J., Yang, J. K. W., Molnar, R. J., Dauler, E. A., & Berggren, K. K. (2009). Electrothermal feedback in superconducting nanowire single-photon detectors. Phys. Rev. B, 79(10), 4.
Abstract: We investigate the role of electrothermal feedback in the operation of superconducting nanowire single-photon detectors (SNSPDs). It is found that the desired mode of operation for SNSPDs is only achieved if this feedback is unstable, which happens naturally through the slow electrical response associated with their relatively large kinetic inductance. If this response is sped up in an effort to increase the device count rate, the electrothermal feedback becomes stable and results in an effect known as latching, where the device is locked in a resistive state and can no longer detect photons. We present a set of experiments which elucidate this effect and a simple model which quantitatively explains the results.
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Ferrari, S., Kovalyuk, V., Vetter, A., Lee, C., Rockstuhl, C., Semenov, A., et al. (2019). Analysis of the detection response of waveguide-integrated superconducting nanowire single-photon detectors at high count rate. Appl. Phys. Lett., 115(10), 101104.
Abstract: Nanophotonic circuitry and superconducting nanowires have been successfully combined for detecting single photons, propagating in an integrated photonic circuit, with high efficiency and low noise and timing uncertainty. Waveguide-integrated superconducting nanowire single-photon detectors (SNSPDs) can nowadays be engineered to achieve subnanosecond recovery times and can potentially be adopted for applications requiring Gcps count rates. However, particular attention shall be paid to such an extreme count rate regime since artifacts in the detector functionality emerge. In particular, a count-rate dependent detection efficiency has been encountered that can compromise the accuracy of quantum detector tomography experiments. Here, we investigate the response of waveguide-integrated SNSPDs at high photon flux and identify the presence of parasitic currents due to the accumulation of charge in the readout electronics to cause the above-mentioned artifact in the detection efficiency. Our approach allows us to determine the maximum photon count rate at which the detector can be operated without adverse effects. Our findings are particularly important to avoid artifacts when applying SNSPDs for quantum tomography.
We acknowledge support through ERC Consolidator Grant No. 724707 and from the Deutsche Forschungsgemeinschaft through Project No. PE 1832/5-1,2, as well as funding by the Volkswagen Foundation. This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 675745. V.K. and G.G. acknowledge support from the Russian Science Foundation Project No. 16-12-00045 (NbN film deposition and testing). A.V. acknowledges support from the Karlsruhe School of Optics and Photonics (KSOP).
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Vodolazov, D. Y., Korneeva, Y. P., Semenov, A. V., Korneev, A. A., & Goltsman, G. N. (2015). Vortex-assisted mechanism of photon counting in a superconducting nanowire single-photon detector revealed by external magnetic field. Phys. Rev. B, 92(10), 104503 (1 to 9).
Abstract: We use an external magnetic field to probe the detection mechanism of a superconducting nanowire single-photon detector. We argue that the hot belt model (which assumes partial suppression of the superconducting order parameter Δ across the whole width of the superconducting nanowire after absorption of the photon) does not explain observed weak-field dependence of the photon count rate (PCR) for photons with λ=450nm and noticeable decrease of PCR (with increasing the magnetic field) in a range of the currents for photons with wavelengths λ=450–1200nm. Found experimental results for all studied wavelengths can be explained by the vortex hot spot model (which assumes partial suppression of Δ in the area with size smaller than the width of the nanowire) if one takes into account nucleation and entrance of the vortices to the photon induced hot spot and their pinning by the hot spot with relatively large size and strongly suppressed Δ.
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Lusche, R., Semenov, A., Korneeva, Y., Trifonov, A., Korneev, A., Gol'tsman, G., et al. (2014). Effect of magnetic field on the photon detection in thin superconducting meander structures. Phys. Rev. B, 89(10), 104513 (1 to 7).
Abstract: We have studied the influence of an externally applied magnetic field on the photon and dark count rates of meander-type niobium nitride superconducting nanowire single-photon detectors. Measurements have been performed at a temperature of 4.2 K, and magnetic fields up to 250 mT have been applied perpendicularly to the meander plane. While photon count rates are field independent at weak applied fields, they show a strong dependence at fields starting from approximately ±25 mT. This behavior, as well as the magnetic field dependence of the dark count rates, is in good agreement with the recent theoretical model of vortex-assisted photon detection and spontaneous vortex crossing in narrow superconducting lines. However, the local reduction of the superconducting free energy due to photon absorption, which is the fitting parameter in the model, increases much slower with the photon energy than the model predicts. Furthermore, changes in the free-energy during photon counts and dark counts depend differently on the current that flows through the meander. This indicates that photon counts and dark counts occur in different parts of the meander.
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Kerman, A. J., Dauler, E. A., Yang, J. K. W., Rosfjord, K. M., Anant, V., Berggren, K. K., et al. (2007). Constriction-limited detection efficiency of superconducting nanowire single-photon detectors. Appl. Phys. Lett., 90(10), 101110 (1 to 3).
Abstract: We investigate the source of the large variations in the observed detection efficiencies of superconducting nanowire single-photon detectors between many nominally identical devices. Through both electrical and optical measurements, we infer that these variations arise from “constrictions:” highly localized regions of the nanowires where the effective cross-sectional area for superconducting current is reduced. These constrictions limit the bias-current density to well below its critical value over the remainder of the wire, and thus prevent the detection efficiency from reaching the high values that occur in these devices when they are biased near the critical current density.
This work is sponsored by the United States Air Force under Contract No. FA8721-05-C-0002.
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Terai, H., Miki, S., Yamashita, T., Makise, K., & Wang, Z. (2010). Demonstration of single-flux-quantum readout operation for superconducting single-photon detectors. Appl. Phys. Lett., 97(11), 3.
Abstract: A readout circuit using superconducting single-flux-quantum (SFQ) circuits has been developed to realize an independently addressable array of superconducting single-photon detectors (SSPDs). We tested the SFQ readout circuits by connecting with SSPDs. The error rates of readout circuits were below 10–5 for input signal amplitude of greater than 18.2 μA. Detection efficiencies (DEs) for single-photon incidents were measured both with and without the connection of a readout circuit. The observed DEs traced almost the same curves regardless of the connection of the readout circuit, except that the SSPD is likely to latch by connecting the readout circuit.
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Vetter, A., Ferrari, S., Rath, P., Alaee, R., Kahl, O., Kovalyuk, V., et al. (2016). Cavity-enhanced and ultrafast superconducting single-photon detectors. Nano Lett., 16(11), 7085–7092.
Abstract: Ultrafast single-photon detectors with high efficiency are of utmost importance for many applications in the context of integrated quantum photonic circuits. Detectors based on superconductor nanowires attached to optical waveguides are particularly appealing for this purpose. However, their speed is limited because the required high absorption efficiency necessitates long nanowires deposited on top of the waveguide. This enhances the kinetic inductance and makes the detectors slow. Here, we solve this problem by aligning the nanowire, contrary to usual choice, perpendicular to the waveguide to realize devices with a length below 1 mum. By integrating the nanowire into a photonic crystal cavity, we recover high absorption efficiency, thus enhancing the detection efficiency by more than an order of magnitude. Our cavity enhanced superconducting nanowire detectors are fully embedded in silicon nanophotonic circuits and efficiently detect single photons at telecom wavelengths. The detectors possess subnanosecond decay ( approximately 120 ps) and recovery times ( approximately 510 ps) and thus show potential for GHz count rates at low timing jitter ( approximately 32 ps). The small absorption volume allows efficient threshold multiphoton detection.
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Maingault, L., Tarkhov, M., Florya, I., Semenov, A., Espiau de Lamaëstre, R., Cavalier, P., et al. (2010). Spectral dependency of superconducting single photon detectors. J. Appl. Phys., 107(11), 116103 (1 to 3).
Abstract: We investigate the effect of varying both incoming optical wavelength and width of NbN nanowires on the superconducting single photon detectors (SSPD) detection efficiency. The SSPD are current biased close to critical value and temperature fixed at 4.2 K, far from transition. The experimental results are found to verify with a good accuracy predictions based on the “hot spot model,” whose size scales with the absorbed photon energy. With larger optical power inducing multiphoton detection regime, the same scaling law remains valid, up to the three-photon regime. We demonstrate the validity of applying a limited number of measurements and using such a simple model to reasonably predict any SSPD behavior among a collection of nanowire device widths at different photon wavelengths. These results set the basis for designing efficient single photon detectors operating in the infrared (2–5 μm range).
This work was supported by European projects FP6 STREP “SINPHONIA” (Contract No. NMP4-CT-2005-16433) and IP “QAP” (Contract No. 15848).
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Kerman, A. J., Dauler, E. A., Keicher, W. E., Yang, J. K. W., Berggren, K. K., Gol’tsman, G., et al. (2006). Kinetic-inductance-limited reset time of superconducting nanowire photon counters. Appl. Phys. Lett., 88(11), 111116 (1 to 3).
Abstract: We investigate the recovery of superconducting NbN-nanowire photon counters after detection of an optical pulse at a wavelength of 1550nm, and present a model that quantitatively accounts for our observations. The reset time is found to be limited by the large kinetic inductance of these nanowires, which forces a tradeoff between counting rate and either detection efficiency or active area. Devices of usable size and high detection efficiency are found to have reset times orders of magnitude longer than their intrinsic photoresponse time.
The authors acknowledge D. Oates and W. Oliver (MIT Lincoln Laboratory), S.W. Nam, A. Miller, and R. Hadfield (NIST) and R. Sobolewski, A. Pearlman, and A. Verevkin (University of Rochester) for helpful discussions and technical assistance. This work made use of MIT’s shared scanning-electron-beam-lithography facility in the Research Laboratory of Electronics. This work is sponsored by the United States Air Force under Air Force Contract No. FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the authors and are not necessarily endorsed by the United States Government.
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Il'in, K. S., Verevkin, A. A., Gol'tsman, G. N., & Sobolewski, R. (1999). Infrared hot-electron NbN superconducting photodetectors for imaging applications. Supercond. Sci. Technol., 12(11), 755–758.
Abstract: We report an effective quantum efficiency of 340, responsivity >200 A W-1 (>104 V W-1) and response time of 27±5 ps at temperatures close to the superconducting transition for NbN superconducting hot-electron photodetectors (HEPs) in the near-infrared and optical ranges. Our studies were performed on a few nm thick NbN films deposited on sapphire substrates and patterned into µm-size multibridge detector structures, incorporated into a coplanar transmission line. The time-resolved photoresponse was studied by means of subpicosecond electro-optic sampling with 100 fs wide laser pulses. The quantum efficiency and responsivity studies of our photodetectors were conducted using an amplitude-modulated infrared beam, fibre-optically coupled to the device. The observed picosecond response time and the very high efficiency and sensitivity of the NbN HEPs make them an excellent choice for infrared imaging photodetectors and input optical-to-electrical transducers for superconducting digital circuits.
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