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Author Ferrari, S.; Kovalyuk, V.; Hartmann, W.; Vetter, A.; Kahl, O.; Lee, C.; Korneev, A.; Rockstuhl, C.; Gol'tsman, G.; Pernice, W.
Title Hot-spot relaxation time current dependence in niobium nitride waveguide-integrated superconducting nanowire single-photon detectors Type Journal Article
Year 2017 Publication Opt. Express Abbreviated Journal Opt. Express
Volume 25 Issue 8 Pages 8739-8750
Keywords SSPD, SNSPD, photon counting; Infrared; Quantum detectors; Integrated optics; Multiphoton processes; Photon statistics
Abstract We investigate how the bias current affects the hot-spot relaxation dynamics in niobium nitride. We use for this purpose a near-infrared pump-probe technique on a waveguide-integrated superconducting nanowire single-photon detector driven in the two-photon regime. We observe a strong increase in the picosecond relaxation time for higher bias currents. A minimum relaxation time of (22 +/- 1)ps is obtained when applying a bias current of 50% of the switching current at 1.7 K bath temperature. We also propose a practical approach to accurately estimate the photon detection regimes based on the reconstruction of the measured detector tomography at different bias currents and for different illumination conditions.
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Call Number RPLAB @ kovalyuk @ Serial (down) 1118
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Author Semenov, A. V.; Devyatov, I. A.; Ryabchun, S. A.; Maslennikov, S. N.; Maslennikova, A. S.; Larionov, P. A.; Voronov, B. M.; Chulkova, G. M.
Title Absorption of terahertz electromagnetic radiation in dirty superconducting film at arbitrary type of the spectral functions Type Journal Article
Year 2011 Publication Rus. J. Radio Electron. Abbreviated Journal Rus. J. Radio Electron.
Volume Issue 10 Pages
Keywords terahertz electromagnetic radiation; superconductors; detectors of terahertz range
Abstract A problem of absorption of high-frequency electromagnetic field in dirty superconductor is treated within Keldysh technic. Expression for the source term in the kinetic equation for quasiparticle distribution function is derived. The result is significant for deriving a consistent microscopic theory of superconducting detectors for terahertz frequency range, perspective detectors on kinetic inductance of current-biased superconducting strip and on Josephson inductance of tunnel.
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Notes 7 pages Approved no
Call Number Serial (down) 1117
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Author Korneeva, Yuliya; Florya, Irina; Vdovichev, Sergey; Moshkova, Mariya; Simonov, Nikita; Kaurova, Natalia; Korneev, Alexander; Goltsman, Gregory
Title Comparison of hot-spot formation in NbN and MoN thin superconducting films after photon absorption Type Conference Article
Year 2017 Publication IEEE Transactions on Applied Superconductivity Abbreviated Journal IEEE Transactions on Applied Superconductiv
Volume 27 Issue 4 Pages 5
Keywords Thin film devices, Superconducitng photoncounting devices, Nanowire single-photon detectors
Abstract In superconducting single-photon detectors SSPD

the efficiency of local suppression of superconductivity and hotspot

formation is controlled by diffusivity and electron-phonon

interaction time. Here we selected a material, 3.6-nm-thick MoNx

film, which features diffusivity close to those of NbN traditionally

used for SSPD fabrication, but with electron-phonon interaction

time an order of magnitude larger. In MoNx detectors we study

the dependence of detection efficiency on bias current, photon

energy, and strip width and compare it with NbN SSPD. We

observe non-linear current-energy dependence in MoNx SSPD

and more pronounced plateaus in dependences of detection

efficiency on bias current which we attribute to longer electronphonon

interaction time.
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Notes Approved no
Call Number RPLAB @ kovalyuk @ Serial (down) 1114
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Author Shurakov, A.; Tong, Cheuk-yu E.; Grimes, P.; Blundell, R.; Golt'sman, G.
Title A microwave reflection readout scheme for hot electron bolometric direct detector Type Journal Article
Year 2015 Publication IEEE Trans. THz Sci. Technol. Abbreviated Journal IEEE Trans. THz Sci. Technol.
Volume 5 Issue Pages 81-84
Keywords HEB detectors
Abstract In this paper, we propose and present data from a fast THz detector based on the repurpose of hot electron bolometer mixers (HEB) fabricated from superconducting NbN thinfilm. This detector is essentially a traditional NbN bolometer element that operates under the influence of a microwave pump. The in-jected microwave power serves the dual purpose of enhancing the detector sensitivity and reading out the impedance changes of the device in response to incidentTHz radiation. We have measured an optical Noise Equivalent Power of 4 pW/ Hz for our detector at a bath temperature of 4.2 K. The measurement frequency was 0.83 THz and the modulation frequency was 1.48 kHz. The readout

scheme is versatile and facilitates both high-speed operation as well as multi-pixel applications.
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Call Number RPLAB @ atomics90 @ Serial (down) 950
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Author D. Henrich, L. Rehm S. Dörner, M. Hofherr, K. Il'in, A. Semenov, and M. Siegel
Title Detection efficiency of a spiral-nanowire superconducting single-photon detector Type Journal Article
Year 2012 Publication Abbreviated Journal
Volume Issue Pages
Keywords Critical current, Nanoscale devices, Superconducting photodetectors.
Abstract We investigate the detection efficiency of a spiral layout of a Superconducting Nanowire Single-Photon Detector (SNSPD). The design is less susceptible to the critical current reduction in sharp turns of the nanowire than the conventional meander design. Detector samples with different nanowire width from 300 to 100 nm are patterned from a 4 nm thick NbN film deposited on sapphire substrates. The critical current IC at 4.2 K for spiral, meander, and simple bridge structures is measured and compared. On the 100 nm wide samples, the detection efficiency is measured in the wavelength range 400-1700 nm and the cut-off wavelength of the hot-spot plateau is determined. In the optical range, the spiral detector reaches a detection efficiency of 27.6%, which is ~1.5 times the value of the meander. In the infrared range the detection efficiency is more than doubled.
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Corporate Author D. Henrich, L. Rehm S. Dörner, M. Hofherr, K. Il'in, A. Semenov, and M. Siegel Thesis
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Notes Approved no
Call Number RPLAB @ seleznev @ Serial (down) 880
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