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Dauler, E. A., Robinson, B. S., Kerman, A. J., Yang, J. K. W., Rosfjord, E. K. M., Anant, V., et al. (2007). Multi-element superconducting nanowire single-photon detector. IEEE Trans. Appl. Supercond., 17(2), 279–284.
Abstract: A multi-element superconducting nanowire single photon detector (MESNSPD) is presented that consists of multiple independently-biased superconducting nanowire single photon detector (SNSPD) elements that form a continuous active area. A two-element SNSPD has been fabricated and tested, showing no measurable crosstalk between the elements, sub-50-ps relative timing jitter, and four times the maximum counting rate of a single SNSPD with the same active area. The MESNSPD can have a larger active area and higher speed than a single-element SNSPD and the input optics can be designed so that the detector provides spatial, spectral or photon number resolution.
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Slysz, W., Wegrzecki, M., Bar, J., Grabiec, P., Gorska, M., Rieger, E., et al. (2007). Fiber-coupled NbN superconducting single-photon detectors for quantum correlation measurements. In M. Dusek, M. S. Hillery, W. P. Schleich, I. Prochazka, A. L. Migdall, & A. Pauchard (Eds.), Proc. SPIE (Vol. 6583, 65830J (1 to 11)). Spie.
Abstract: We have fabricated fiber-coupled superconducting single-photon detectors (SSPDs), designed for quantum-correlationtype experiments. The SSPDs are nanostructured ( 100-nm wide and 4-nm thick) NbN superconducting meandering stripes, operated in the 2 to 4.2 K temperature range, and known for ultrafast and efficient detection of visible to nearinfrared photons with almost negligible dark counts. Our latest devices are pigtailed structures with coupling between the SSPD structure and a single-mode optical fiber achieved using a micromechanical photoresist ring placed directly over the meander. The above arrangement withstands repetitive thermal cycling between liquid helium and room temperature, and we can reach the coupling efficiency of up to 33%. The system quantum efficiency, measured as the ratio of the photons counted by SSPD to the total number of photons coupled into the fiber, in our early devices was found to be around 0.3 % and 1% for 1.55 &mgr;m and 0.9 &mgr;m photon wavelengths, respectively. The photon counting rate exceeded 250 MHz. The receiver with two SSPDs, each individually biased, was placed inside a transport, 60-liter liquid helium Dewar, assuring uninterrupted operation for over 2 months. Since the receiver’s optical and electrical connections are at room temperature, the set-up is suitable for any applications, where single-photon counting capability and fast count rates are desired. In our case, it was implemented for photon correlation experiments. The receiver response time, measured as a second-order photon cross-correlation function, was found to be below 400 ps, with timing jitter of less than 40 ps.
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Zinoni, C., Alloing, B., Li, L. H., Marsili, F., Fiore, A., Lunghi, L., et al. (2007). Single-photonics at telecom wavelengths using nanowire superconducting single photon detectors. In CLEO/QELS (QTuF6 (1 to 2)). Optical Society of America.
Abstract: Novel single-photon detectors based on NbN superconducting nanostructures promise orders-of- magnitude improvement over InGaAs APDs. We demonstrate this improved performance for the first time by measuring the g(2)(τ) on single photon states produced by a quantum dot at telecom wavelength.
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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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Słysz, W., Wegrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2007). Fibre-coupled, single photon detector based on NbN superconducting nanostructures for quantum communications. J. Modern Opt., 54(2-3), 315–326.
Abstract: We present a novel, two-channel, single photon receiver based on two fibre-coupled, NbN, superconducting, single photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders and are known for ultrafast and efficient detection of visible-to-infrared photons. Coupling between the NbN detector and optical fibre was achieved using a micromechanical photoresist ring placed directly over the SSPD, holding the fibre in place. With this arrangement, we obtained coupling efficiencies up to ∼30%. Our experimental results showed that the best receiver had a near-infrared system quantum efficiency of 0.33% at 4.2 K. The quantum efficiency increased exponentially with the photon energy increase, reaching a few percent level for visible-light photons. The photoresponse pulses of our devices were limited by the meander high kinetic inductance and had the rise and fall times of approximately 250 ps and 5 ns, respectively. The receiver's timing jitter was in the 37 to 58 ps range, approximately 2 to 3 times larger than in our older free-space-coupled SSPDs. We stipulate that this timing jitter is in part due to optical fibre properties. Besides quantum communications, the two-detector arrangement should also find applications in quantum correlation experiments.
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Rosfjord, K. M., Yang, J. K. W., Dauler, E. A., Kerman, A. J., Vikas Anant, Voronov, B. M., et al. (2006). Nanowire Single-photon detector with an integrated optical cavity and anti-reflection coating. Opt. Express, 14(2), 527–534.
Abstract: We have fabricated and tested superconducting single-photon detectors and demonstrated detection efficiencies of 57% at 1550-nm wavelength and 67% at 1064 nm. In addition to the peak detection efficiency, a median detection efficiency of 47.7% was measured over 132 devices at 1550 nm. These measurements were made at 1.8K, with each device biased to 97.5% of its critical current. The high detection efficiencies resulted from the addition of an optical cavity and anti-reflection coating to a nanowire photodetector, creating an integrated nanoelectrophotonic device with enhanced performance relative to the original device. Here, the testing apparatus and the fabrication process are presented. The detection efficiency of devices before and after the addition of optical elements is also reported.
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Chulkova, G., Milostnaya, I., Tarkhov, M., Korneev, A., Minaeva, O., Voronov, B., et al. (2006). Superconducting single-photon nanostructured detectors for advanced optical applications. In Proc. Symposium on Photonics Technologies for 7th Framework Program (Vol. 400).
Abstract: We present superconducting single-photon detectors (SSPDs) based on NbN thin-film nanostructures and operated at liquid helium temperatures. The SSPDs are made of ultrathin NbN films (2.5-4 nm thick, Tc= 9-11K) as meander-shaped nanowires covering the area of 10× 10 µm2. Our detectors are operated at the temperature well below the critical temperature Tc and are DC biased by a current Ib close to the meander critical current Ic. The operation principle of the detector is based on the use of the resistive region in a narrow ultra-thin superconducting stripe upon the absorption of an incident photon. The developed devices demonstrate high sensitivity and response speed in a broadband range from UV to mid-IR (up to 6 µm), making them very attractive for advanced optical technologies, which require efficient detectors of single quanta and low-density optical radiation.
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Tarkhov, M., Morozov, D., Mauskopf, P., Seleznev, V., Korneev, A., Kaurova, N., et al. (2006). Single photon counting detector for THz radioastronomy. In Proc. 17th Int. Symp. Space Terahertz Technol. (pp. 119–122).
Abstract: In this paper we present the results of the research on the superconducting NbN-ultrathin-film single- photon detectors (SSPD) which are capable to detect single quanta in middle IR range. The detection mechanism is based on the hotspot formation in quasi-two-dimensional superconducting structures upon photon absorption. Spectral measurements showed that up to 5.7 gm wavelength (52 THz) the SSPD exhibits single-photon sensitivity. Reduction of operation temperature to 1.6 K allowed us to measure quantum efficiency of -4% at 60 THz. Although further decrease of the operation temperature far below 1 K does not lead to any significant increase of quantum efficiency. We expect that the improvement of the SSPD's performance at reduced operation temperature will make SSPD a practical detector with high characteristics for much lower THz frequencies as well.
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Smirnov, K., Korneev, A., Minaeva, O., Divochij, A., Rubtsova, I., Antipov, A., et al. (2006). Superconducting single-photon detector for near- and middle IR wavelength range. In Proc. 16th Int. Crimean Microwave and Telecommunication Technology (Vol. 2, pp. 684–685).
Abstract: Presented in this paper are the results of research of NbN-film superconducting single-photon detector. At 2 K temperature, quantum efficiency in the visible light (0.56 mum) reaches 30-40 %. With the wavelength increase quantum efficiency decreases and comes to 20% at 1.55 mum and 0.02% at 5.6 mum. Minimum dark counts rate is 2times10-4s-1. The jitter of detector is 35 ps. The detector was successfully implemented for integrated circuits non-invasive optical testing. It is also perspective for quantum cryptography systems
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Słysz, W., Węgrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2006). Fiber-coupled single-photon detectors based on NbN superconducting nanostructures for practical quantum cryptography and photon-correlation studies. Appl. Phys. Lett., 88(26), 261113 (1 to 3).
Abstract: We have fabricated and tested a two-channel single-photon detector system based on two fiber-coupled superconducting single-photon detectors (SSPDs). Our best device reached the system quantum efficiency of 0.3% in the 1540-nm telecommunication wavelength with a fiber-to-detector coupling factor of about 30%. The photoresponse consisted of 2.5-ns-wide voltage pulses with a rise time of 250ps and timing jitter below 40ps. The overall system response time, measured as a second-order, photon cross-correlation function, was below 400ps. Our SSPDs operate at 4.2K inside a liquid-helium Dewar, but their optical fiber inputs and electrical outputs are at room temperature. Our two-channel detector system should find applications in practical quantum cryptography and in antibunching-type quantum correlation measurements.
The authors would like to thank Dr. Marc Currie for his assistance in early time-resolved photoresponse measurements and Professor Atac Imamoglu for his support. This work was supported by the Polish Ministry of Science under Project No. 3 T11B 052 26 (Warsaw), RFBR 03-02-17697 and INTAS 03-51-4145 grants (Moscow), CRDF Grant No. RE2-2531-MO-03 (Moscow), RE2-2529-MO-03 (Moscow and Rochester), and US AFOSR FA9550-04-1-0123 (Rochester). Additional funding was provided by the grants from the MIT Lincoln Laboratory and BBN Technologies Corp.
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Milostnaya, I., Korneev, A., Rubtsova, I., Seleznev, V., Minaeva, O., Chulkova, G., et al. (2006). Superconducting single-photon detectors designed for operation at 1.55-µm telecommunication wavelength. In J. Phys.: Conf. Ser. (Vol. 43, pp. 1334–1337).
Abstract: We report on our progress in development of superconducting single-photon detectors (SSPDs), specifically designed for secure high-speed quantum communications. The SSPDs consist of NbN-based meander nanostructures and operate at liquid helium temperatures. In general, our devices are capable of GHz-rate photon counting in a spectral range from visible light to mid-infrared. The device jitter is 18 ps and dark counts can reach negligibly small levels. The quantum efficiency (QE) of our best SSPDs for visible-light photons approaches a saturation level of ~30-40%, which is limited by the NbN film absorption. For the infrared range (1.55µm), QE is ~6% at 4.2 K, but it can be significantly improved by reduction of the operation temperature to the 2-K level, when QE reaches ~20% for 1.55-µm photons. In order to further enhance the SSPD efficiency at the wavelength of 1.55 µm, we have integrated our detectors with optical cavities, aiming to increase the effective interaction of the photon with the superconducting meander and, therefore, increase the QE. A successful effort was made to fabricate an advanced SSPD structure with an optical microcavity optimized for absorption of 1.55 µm photons. The design consisted of a quarter-wave dielectric layer, combined with a metallic mirror. Early tests performed on relatively low-QE devices integrated with microcavities, showed that the QE value at the resonator maximum (1.55-µm wavelength) was of the factor 3-to-4 higher than that for a nonresonant SSPD. Independently, we have successfully coupled our SSPDs to single-mode optical fibers. The completed receivers, inserted into a liquid-helium transport dewar, reached ~1% system QE for 1.55 µm photons. The SSPD receivers that are fiber-coupled and, simultaneously, integrated with resonators are expected to be the ultimate photon counters for optical quantum communications.
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Dauler, E. A., Kerman, A. J., Robinson, B. S., Yang, J. K. W., Voronov, B. M., Gol’tsman, G. N., et al. (2006). Achieving high counting rates in superconducting nanowire single-photon detectors. In CLEO/QELS (JTuD3 (1 to 2)). Optical Society of America.
Abstract: Kinetic inductance is determined to be the primary limitation to the counting rate of superconducting nanowire single-photon counters. Approaches for overcoming this limitation will be discussed.
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Rosfjord, K. M., Yang, J. K. W., Dauler, E. A., Anant, V., Berggren, K. K., Kerman, A. J., et al. (2006). Increased detection efficiencies of nanowire single-photon detectors by integration of an optical cavity and anti-reflection coating. In CLEO/QELS (JTuF2 (1 to 2)).
Abstract: We fabricate and test superconducting NbN-nanowire single-photon detectors with an integrated optical cavity and anti-reflection coating. We design the cavity and coating such as to maximize absorption in the NbN film of the detector.
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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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Корнеев, А. А., Минаева, О., Рубцова, И., Милостная, И., Чулкова, Г., Воронов, Б., et al. (2005). Сверхпроводящий однофотонный детектор на основе ультратонкой пленки NbN. Квантовая электроника, 35(8), 698–700.
Abstract: Представлены результаты исследований сверхпроводящих однофотонных детекторов, изготовленных из ультратонкой пленки NbN. Развитие технологического процесса изготовления детекторов, а также снижение рабочей температуры до 2 К позволили существенно увеличить квантовую эффективность: для видимого света (λ = 0.56 мкм) она составила 30%–40%, т.е. достигла предела, определяемого коэффициентом поглощения пленки. С ростом длины волны квантовая эффективность экспоненциально падает, составляя ~20% на λ=1.55 мкм и ~0.02% на λ = 5 мкм. При скорости темнового счета ~10-4s-1 экспериментально измеренная эквивалентная мощность шума составила 1.5 × 10-20 Вт/Гц-1/2; в дальнейшем она может быть уменьшена до рекордно низкого значения 5 × 10-21 Вт/Гц-1/2. Временное разрешение детектора равно 30 пс.
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