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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Korneev, A., Divochiy, A., Tarkhov, M., Minaeva, O., Seleznev, V., Kaurova, N., et al. (2008). New advanced generation of superconducting NbN-nanowire single-photon detectors capable of photon number resolving. In J. Phys.: Conf. Ser. (Vol. 97, 012307 (1 to 6)).
Abstract: We present our latest generation of ultrafast superconducting NbN single-photon detectors (SSPD) capable of photon-number resolving (PNR). We have developed, fabricated and tested a multi-sectional design of NbN nanowire structures. The novel SSPD structures consist of several meander sections connected in parallel, each having a resistor connected in series. The novel SSPDs combine 10 μm × 10 μm active areas with a low kinetic inductance and PNR capability. That resulted in a significantly reduced photoresponse pulse duration, allowing for GHz counting rates. The detector's response magnitude is directly proportional to the number of incident photons, which makes this feature easy to use. We present experimental data on the performances of the PNR SSPDs. The PNR SSPDs are perfectly suited for fibreless free-space telecommunications, as well as for ultrafast quantum cryptography and quantum computing.
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Korneev, A., Divochiy, A., Marsili, F., Bitauld, D., Fiore, A., Seleznev, V., et al. (2008). Superconducting photon number resolving counter for near infrared applications. In P. Tománek, D. Senderáková, & M. Hrabovský (Eds.), Proc. SPIE (Vol. 7138, 713828 (1 to 5)). Spie.
Abstract: We present a novel concept of photon number resolving detector based on 120-nm-wide superconducting stripes made of 4-nm-thick NbN film and connected in parallel (PNR-SSPD). The detector consisting of 5 strips demonstrate a capability to resolve up to 4 photons absorbed simultaneously with the single-photon quantum efficiency of 2.5% and negligibly low dark count rate.
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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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Korneev, A., Divochiy, A., Tarkhov, M., Minaeva, O., Seleznev, V., Kaurova, N., et al. (2008). Superconducting NbN-nanowire single-photon detectors capable of photon number resolving. In Supercond. News Forum.
Abstract: We present our latest generation of ultra-fast superconducting NbN single-photon detectors (SSPD) capable of photon-number resolving (PNR). The novel SSPDs combine 10 μm x 10 μm active area with low kinetic inductance and PNR capability. That resulted in significantly reduced photoresponse pulse duration, allowing for GHz counting rates. The detector’s response magnitude is directly proportional to the number of incident photons, which makes this feature easy to use. We present experimental data on the performance of the PNR SSPDs. These detectors are perfectly suited for fibreless free-space telecommunications, as well as for ultra-fast quantum cryptography and quantum computing.
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Smirnov, K. V., Vachtomin, Y. B., Ozhegov, R. V., Pentin, I. V., Slivinskaya, E. V., Korneev, A. A., et al. (2008). Fiber coupled single photon receivers based on superconducting detectors for quantum communications and quantum cryptography. In P. Tománek, D. Senderáková, & M. Hrabovský (Eds.), Proc. SPIE (Vol. 7138, 713827 (1 to 6)). Spie.
Abstract: At present superconducting detectors become increasingly attractive for various practical applications. In this paper we present results on the depelopment of fiber coupled receiver systems for the registration of IR single photons, optimized for telecommunication and quantum-cryptography. These receiver systems were developed on the basis of superconducting single photon detectors (SSPD) of VIS and IR wavelength ranges. The core of the SSPD is a narrow ( 100 nm) and long ( 0,5 mm) strip in the form of a meander which is patterned from a 4-nm-thick NbN film (TC=10-11 K, jC= 5-7•106 A/cm2); the sensitive area dimensions are 10×10 μm2. The main problem to be solved while the receiver system development was optical coupling of a single-mode fiber (9 microns in diameter) with the SSPD sensitive area. Characteristics of the developed system at the optical input are as follows: quantum efficiency >10 % (at 1.3 μm), >4 % (at 1.55 μm); dark counts rate ≤1 s-1; duration of voltage pulse ≤5 ns; jitter ≤40 ps. The receiver systems have either one or two identical channels (for the case of carrying out correlation measurements) and are made as an insert in a helium storage Dewar.
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Okunev, O., Chulkova, G., Milostnaya, I., Antipov, A., Smirnov, K., Morozov, D., et al. (2008). Registration of infrared single photons by a two-channel receiver based on fiber-coupled superconducting single-photon detectors. In I. A. Sukhoivanov, V. A. Svich, & Y. S. Shmaliy (Eds.), Proc. SPIE (Vol. 7009, 70090V (1 to 8)). SPIE.
Abstract: Single-photon detectors (SPDs) are the foundation of all quantum communications (QC) protocols. Among different classes of SPDs currently studied, NbN superconducting SPDs (SSPDs) are established as the best devices for ultrafast counting of single photons in the infrared (IR) wavelength range. The SSPDs are nanostructured, 100 μm2 in total area, superconducting meanders, patterned by electron lithography in ultra-thin NbN films. Their operation has been explained within a phenomenological hot-electron photoresponse model. We present the design and performance of a novel, two-channel SPD receiver, based on two fiber-coupled NbN SSPDs. The receivers have been developed for fiber-based QC systems, operational at 1.3 μm and 1.55 μm telecommunication wavelengths. They operate in the temperature range from 4.2 K to 2 K, in which the NbN SSPDs exhibit their best performance. The receiver unit has been designed as a cryostat insert, placed inside a standard liquid-heliumstorage dewar. The input of the receiver consists of a pair of single-mode optical fibers, equipped with the standard FC connectors and kept at room temperature. Coupling between the SSPD and the fiber is achieved using a specially designed, precise micromechanical holder that places the fiber directly on top of the SSPD nanostructure. Our receivers achieve the quantum efficiency of up to 7% for near-IR photons, with the coupling efficiency of about 30%. The response time was measured to be < 1.5 ns and it was limited by our read-out electronics. The jitter of fiber-coupled SSPDs is < 35 ps and their dark-count rate is below 1s-1. The presented performance parameters show that our single-photon receivers are fully applicable for quantum correlation-type QC systems, including practical quantum cryptography.
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Jukna, A., Kitaygorsky, J., Pan, D., Cross, A., Perlman, A., Komissarov, I., et al. (2008). Dynamics of hotspot formation in nanostructured superconducting stripes excited with single photons. Acta Physica Polonica A, 113(3), 955–958.
Abstract: Dynamics of a resistive hotspot formation by near-infrared-wavelength single photons in nanowire-type superconducting NbN stripes was investigated. Numerical simulations of ultrafast thermalization of photon-excited nonequilibrium quasiparticles, their multiplication and out-diffusion from a site of the photon absorption demonstrate that 1.55 μm wavelength photons create in an ultrathin, two-dimensional superconducting film a resistive hotspot with the diameter which depends on the photon energy, and the nanowire temperature and biasing conditions. Our hotspot model indicates that under the subcritical current bias of the 2D stripe, the electric field penetrates the superconductor at the hotspot boundary, leading to suppression of the stripe superconducting properties and accelerated development of a voltage transient across the stripe.
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Goltsman, G., Korneev, A., Divochiy, A., Minaeva, O., Tarkhov, M., Kaurova, N., et al. (2009). Ultrafast superconducting single-photon detector. J. Modern Opt., 56(15), 1670–1680.
Abstract: The state-of-the-art of the NbN nanowire superconducting single-photon detector technology (SSPD) is presented. The SSPDs exhibit excellent performance at 2 K temperature: 30% quantum efficiency from visible to infrared, negligible dark count rate, single-photon sensitivity up to 5.6 µm. The recent achievements in the development of GHz counting rate devices with photon-number resolving capability is presented.
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Ozhegov, R. V., Smirnov, A. V., Vakhtomin, Y. B., Smirnov, K. V., Divochiy, A. V., & Goltsman, G. N. (2009). Ultrafast superconducting bolometer receivers for terahertz applications. In Proc. PIERS (867). 777 Concord Avenue, Suite 207 Cambridge, MA 02138: The Electromagnetics Academy.
Abstract: The research by the group of Moscow State Pedagogical University into the hot-electron phenomena in thin superconducting films has led to the development of new types of detectors and their use both in fundamental and applied studies. In this paper, we present the results of testing the terahertz HEB receiver systems based on ultrathin (∼ 4 nm) NbN and MoRe detectors with a response time of 50 ps and 1 ns, respectively. We have developed three types of devices which differ in the way a terahertz signal is coupled to the detector and cover the following ranges: 0.3–3 THz, 0.1–30 THz and 25–70 THz. In the case of the receiving system optimized for 0.3–3 THz, the sensitive element (a strip of asuperconductor with planar dimensions of 0.2μm (length) by 1.7μm (width)) was integrated witha planar broadband log-spiral antenna. For additional focusing ofthe incident radiation a silicon hyperhemispherical lens was used. For the 0.1–30 THz receivingsystem, the sensitive element was patterned as parallel strips(2μm wide each) filling an area of 500×500μm2with a filling factor of 0.5. In the receivingsystem of this type we used direct coupling of the incident radiation to the sensitive element. Inthe 25–70 THz range (detector type 2/2a in Table 1) we used a square-shaped superconductingdetector with planar dimensions of 10×10μm2. Incident radiation was coupled to the detectorwith the use of a germanium hyperhemispherical lens.The response time of the above receiving systems is determined by the cooling rate of the hotelectrons in the film. That depends on the electron-phonon interaction time, which is less forultrathin NbN than in MoRe.
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Smirnov, K. V., Vakhtomin, Y. B., Divochiy, A. V., Ozhegov, R. V., Pentin, I. V., Slivinskaya, E. V., et al. (2009). Single-photon detectors for the visible and infrared parts of the spectrum based on NbN nanostructures. In Proc. Progress In Electromagnetics Research Symp. (pp. 863–864). Moscow, Russia.
Abstract: The research by the group of Moscow State Pedagogical University into the hot-electron phenomena in thin superconducting films has led to the development of new types ofdetectors [1, 2] and their use both in fundamental and applied studies [3–6]. In this paper, wepresent the results of the development and fabrication of receiving systems for the visible andinfrared parts of the spectrum optimised for use in telecommunication systems and quantumcryptography.
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Ozhegov, R. V., Gorshkov, K. N., Smirnov, K. V., Gol’tsman, G. N., Filippenko, L. V., & Koshelets, V. P. (2010). Terahertz imaging system based on superconducting integrated receiver. In Proc. 2-nd Int. Conf. Terahertz and Microwave radiation: Generation, Detection and Applications (pp. 20–22).
Abstract: The development of terahertz imaging instruments for security systems is on the cutting edge of terahertz technology. We are developing a THz imaging system based on a superconducting integrated receiver (SIR). An SIR is a new type of heterodyne receiver based on an SIS mixer integrated with a flux-flow oscillator (FFO) and a harmonic mixer which is used for phase-locking the FFO. Developing an array of SIRs would allow obtaining amplitude and phase characteristics of incident radiation in the plane of the receiver. Employing an SIR in an imaging system means building an entirely new instrument with many advantages compare to traditional systems: i) high temperature resolution, comparable to the best results for incoherent receivers; ii) high spectral resolution allowing spectral analysis of various substances; iii) the local oscillator frequency can be varied to obtain images at different frequencies, effectively providing “color” images; iv) since a heterodyne receiver preserves the phase of the radiation, it is possible to construct 3D images. The paper presents a prototype THz imaging system using an 1 pixel SIR. We have studied the dependence of the noise equivalent temperature difference (NETD) on the integration time and also possible ways of achieving best possible sensitivity. An NETD of 13 mK was obtained with an integration time of 1 sec a detection bandwidth of 4 GHz at a local oscillator frequency of 520 GHz. An important advantage of an FFO is its wide operation range: 300-700 GHz.
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Elvira, D., Michon, A., Fain, B., Patriarche, G., Beaudoin, G., Robert-Philip, I., et al. (2010). Time-resolved spectroscopy of InAsP/InP(001) quantum dots emitting near 2 μm. Appl. Phys. Lett., 97(13), 131907 (1 to 3).
Abstract: By using superconducting single photon detectors, we perform time-resolved characterization of a small ensemble of InAsP/InP quantum dots grown by metal organic vapor phase epitaxy, emitting at wavelengths between 1.6 and 2.2 μm. We demonstrate that alloying phosphorus with InAs allows to shift the emission wavelength toward higher wavelengths, while keeping the high optical quality of these quantum dots at room temperature, with no decrease in their radiative lifetime. This work was partially supported by Russian Ministry of Science and Education: Federal State Program “Scientific and Educational Cadres of Innovative” state Contract Nos. 02.740.0228, 14.740.11.0343, 14.740.11.0269, and P931, and RFBR Project No. 09-02-12364.
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Smirnov, K. V., Vakhtomin, Y. B., Divochiy, A. V., Ozhegov, R. V., Pentin, I. V., & Gol'tsman, G. N. (2010). Infrared and terahertz detectors on basis of superconducting nanostructures. In IEEE (Ed.), Microwave and Telecom. Technol. (CriMiCo), 20th Int. Crimean Conf. (pp. 823–824).
Abstract: Results of development of single-photon receiving systems of visible, infrared and terahertz range based on thin-film superconducting nanostructures are presented. The receiving systems are produced on the basis of superconducting nanostructures, which function by means of hot-electron phenomena.
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Shangina, E. L., Smirnov, K. V., Morozov, D. V., Kovalyuk, V. V., Gol’tsman, G. N., Verevkin, A. A., et al. (2010). Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons. Semicond., 44(11), 1427–1429.
Abstract: The temperature and concentration dependences of the frequency bandwidth of terahertz heterodyne AlGaAs/GaAs detectors based on hot electron phenomena with phonon cooling of two-dimensional electrons have been measured by submillimeter spectroscopy with a high time resolution. At a temperature of 4.2 K, the frequency bandwidth at a level of 3 dB (f 3 dB) is varied from 150 to 250 MHz with a change in the concentration n s according to the power law f 3dB ∝ n −0.5 s due to the dominant contribution of piezoelectric phonon scattering. The minimum conversion loss of the semiconductor heterodyne detector is obtained in structures with a high carrier mobility (μ > 3 × 105 cm2 V−1 s−1 at 4.2 K).
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