|
|
Sobolewski, R., Xu, Y., Zheng, X., Williams, C., Zhang, J., Verevkin, A., et al. (2002). Spectral sensitivity of the NbN single-photon superconducting detector. IEICE Trans. Electron., E85-C(3), 797–802.
Abstract: We report our studies on the spectral sensitivity of superconducting NbN thin-film single-photon detectors (SPD's) capable of GHz counting rates of visible and near-infrared photons. In particular, it has been shown that a NbN SPD is sensitive to 1.55-µm wavelength radiation and can be used for quantum communication. Our SPD's exhibit experimentally measured intrinsic quantum efficiencies from 20% at 800 nm up to 1% at 1.55-µm wavelength. The devices demonstrate picosecond response time (<100 ps, limited by our readout system) and negligibly low dark counts. Spectral dependencies of photon counting of continuous-wave, 0.4-µm to 3.5-µm radiation, and 0.63-µm, 1.33-µm, and 1.55-µm laser-pulsed radiations are presented for the single-stripe-type and meander-type devices.
|
|
|
|
Beck, M., Leiderer, P., Kabanov, V. V., Gol'tsman, G., Helm, M., & Demsar, J. (2012). Energy-gap dynamics of a superconductor NbN studied by time-resolved terahertz spectroscopy. In INIS (Vol. 45, pp. 1–3).
Abstract: Using time-resolved terahertz (THz) spectroscopy we performed direct studies of the photoinduced suppression and recovery of the SC gap in a conventional SC NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the important microscopic constants: the Cooper pair-breaking rate via phonon absorption and the bare quasiparticle recombination rate. From the latter we were able to extract the dimensionless electron-phonon coupling constant, λ=1.1±0.1, in excellent agreement with theoretical estimates. The technique also allowed us to determine the absorbed energy required to suppress SC, which in NbN equals the thermodynamic condensation energy (in cuprates the two differ by an order of magnitude). Finally, we present the first studies of dynamics following resonant excitation with intense narrow band THz pulses tuned to above and below the superconducting gap. These suggest an additional process, particularly pronounced near Tc, that could be attributed to amplification of SC via effective quasiparticle cooling.
|
|
|
|
Hübers, H. - W., Semenov, A., Schubert, J., Gol'tsman, G., Voronov, B., & Gershenzon, E. (2000). Performance of the phonon-cooled hot-electron bolometric mixer between 0.7 THz and 5.2 THz. In Proc. 8-th Int. Conf. on Terahertz Electronics (pp. 117–119).
Abstract: We report on the phonon cooled NbN hot electron bolometer as mixer in the terahertz frequency range. Its hybrid antenna consists of a hyperhemispheric silicon lens and a logarithmic-spiral feed antenna. Noise temperatures have been measured between 0.7 THz and 5.2 THz. A quarter wavelength layer of Parylene works as antireflection coating for the silicon lens and reduces the noise temperature by about 30. It was found that the antenna pattern at 2.5 THz is determined by the feed antenna and not by the diameter of the lens.
|
|
|
|
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.
|
|
|
|
Divochiy, A., Marsili, F., Bitauld, D., Gaggero, A., Leoni, R., Mattioli, F., et al. (2008). Superconducting nanowire photon-number-resolving detector at telecommunication wavelengths. Nat. Photon., 2(5), 302–306.
Abstract: Optical-to-electrical conversion, which is the basis of the operation of optical detectors, can be linear or nonlinear. When high sensitivities are needed, single-photon detectors are used, which operate in a strongly nonlinear mode, their response being independent of the number of detected photons. However, photon-number-resolving detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication and quantum information processing, the photon-number-resolving functionality is key to many protocols, such as the implementation of quantum repeaters1 and linear-optics quantum computing2. A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, such as in long-distance optical communications, fluorescence spectroscopy and optical time-domain reflectometry. We demonstrate here a photon-number-resolving detector based on parallel superconducting nanowires and capable of counting up to four photons at telecommunication wavelengths, with an ultralow dark count rate and high counting frequency.
|
|
|
|
Semenov, A. D., Gol'tsman, G. N., & Sobolewski, R. (2002). Hot-electron effect in superconductors and its applications for radiation sensors. Supercond. Sci. Technol., 15(4), R1–R16.
Abstract: The paper reviews the main aspects of nonequilibrium hot-electron phenomena in superconductors and various theoretical models developed to describe the hot-electron effect. We discuss implementation of the hot-electron avalanche mechanism in superconducting radiation sensors and present the most successful practical devices, such as terahertz mixers and direct intensity detectors, for far-infrared radiation. Our presentation also includes the novel approach to hot-electron quantum detection implemented in superconducting x-ray to optical photon counters.
|
|
|
|
Kitaygorsky, J., Komissarov, I., Jukna, A., Sobolewski, R., Minaeva, O., Kaurova, N., et al. (2006). Nanosecond, transient resistive state in two-dimensional superconducting stripes. In Proc. APS March Meeting (H38.13).
Abstract: We have observed, nanosecond-in-duration, transient voltage pulses, generated across two-dimensional (2-D) NbN stripes (width: 100--500 nm; thickness: 3.5--10 nm) of various lengths (1--500 μm), when the wires were completely isolated from the outside world, biased at currents close to the critical current, and kept at temperatures below the mean-field critical temperature Tco. In 2-D superconducting films, at temperatures below the Kosterlitz-Thouless transition, all vortices are bound and the resistance is zero. However, these vortices can get unbound when a large enough transport current is applied. The latter results in a transient resistive state, which manifests itself as spontaneous, 2.5--8-ns-long voltage pulses with the amplitude corresponding to the unbinding potential of a vortex pair. In our 100-nm-wide stripes, we have also observed the formation of phase slip centers (PSCs) at temperatures close to Tco, and a mixture of PSCs and unbound vortex-antivortex pairs at low temperatures.
|
|
|
|
Ryabchun, S., Tong, C. - Y. E., Blundell, R., & Gol'tsman, G. (2009). Stabilization scheme for hot-electron bolometer receivers using microwave radiation. IEEE Trans. Appl. Supercond., 19(1), 14–19.
Abstract: We present the results of a stabilization scheme for terahertz receivers based on NbN hot-electron bolometer (HEB) mixers that uses microwave radiation with a frequency much lower than the gap frequency of NbN to compensate for mixer current fluctuations. A feedback control loop, which actively controls the power level of the injected microwave radiation, has successfully been implemented to stabilize the operating point of the HEB mixer. This allows us to increase the receiver Allan time to 10 s and also improve the temperature resolution of the receiver by about 30% in the total power mode of operation.
|
|
|
|
Korneev, A., Vachtomin, Y., Minaeva, O., Divochiy, A., Smirnov, K., Okunev, O., et al. (2007). Single-photon detection system for quantum optics applications. IEEE J. Select. Topics Quantum Electron., 13(4), 944–951.
Abstract: We describe the design and characterization of a fiber-coupled double-channel single-photon detection system based on superconducting single-photon detectors (SSPD), and its application for quantum optics experiments on semiconductor nanostructures. When operated at 2-K temperature, the system shows 10% quantum efficiency at 1.3-¿m wavelength with dark count rate below 10 counts per second and timing resolution <100 ps. The short recovery time and absence of afterpulsing leads to counting frequencies as high as 40 MHz. Moreover, the low dark count rate allows operation in continuous mode (without gating). These characteristics are very attractive-as compared to InGaAs avalanche photodiodes-for quantum optics experiments at telecommunication wavelengths. We demonstrate the use of the system in time-correlated fluorescence spectroscopy of quantum wells and in the measurement of the intensity correlation function of light emitted by semiconductor quantum dots at 1300 nm.
|
|
|
|
Lobanov, Y., Shcherbatenko, M., Shurakov, A., Rodin, A. V., Klimchuk, A., Nadezhdinsky, A. I., et al. (2014). Heterodyne detection at near-infrared wavelengths with a superconducting NbN hot-electron bolometer mixer. Opt. Lett., 39(6), 1429–1432.
Abstract: We report on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer. The results are important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects, as well as for quantum optical tomography and fiber-optic sensing. Receiver configuration as well as fiber-to-detector light coupling designs are discussed. Light absorption of the superconducting detectors was enhanced by nano-optical antennas, which were coupled to optical fibers. An intermediate frequency (IF) bandwidth of about 3 GHz was found in agreement with measurements at 300 GHz, and a noise figure of about 25 dB was obtained that was only 10 dB above the quantum limit.
|
|
