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Author Kardakova, A.; Finkel, M.; Morozov, D.; Kovalyuk, V.; An, P.; Dunscombe, C.; Tarkhov, M.; Mauskopf, P.; Klapwijk, T.M.; Goltsman, G. doi  openurl
  Title The electron-phonon relaxation time in thin superconducting titanium nitride films Type Journal Article
  Year 2013 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 103 Issue 25 Pages 252602 (1 to 4)  
  Keywords disordered TiN films, electron-phonon relaxation time  
  Abstract We report on the direct measurement of the electron-phonon relaxation time, τeph, in disordered TiN films. Measured values of τeph are from 5.5 ns to 88 ns in the 4.2 to 1.7 K temperature range and consistent with a T−3 temperature dependence. The electronic density of states at the Fermi level N0 is estimated from measured material parameters. The presented results confirm that thin TiN films are promising candidate-materials for ultrasensitive superconducting detectors.

The work was supported by the Ministry of Education and Science of the Russian Federation, Contract No. 14.B25.31.0007 and by the RFBR Grant No. 13-02-91159.
 
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  Call Number RPLAB @ kovalyuk @ Serial 941  
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Author Ferrari, S.; Kahl, O.; Kovalyuk, V.; Goltsman, G. N.; Korneev, A.; Pernice, W. H. P. url  doi
openurl 
  Title Waveguide-integrated single- and multi-photon detection at telecom wavelengths using superconducting nanowires Type Journal Article
  Year 2015 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 106 Issue 15 Pages 151101 (1 to 5)  
  Keywords SSPD, SNSPD  
  Abstract We investigate single- and multi-photon detection regimes of superconducting nanowire detectors embedded in silicon nitride nanophotonic circuits. At near-infrared wavelengths, simultaneous detection of up to three photons is observed for 120 nm wide nanowires biased far from the critical current, while narrow nanowires below 100 nm provide efficient single photon detection. A theoretical model is proposed to determine the different detection regimes and to calculate the corresponding internal quantum efficiency. The predicted saturation of the internal quantum efficiency in the single photon regime agrees well with plateau behavior observed at high bias currents.

W. H. P. Pernice acknowledges support by the DFG Grant Nos. PE 1832/1-1 and PE 1832/1-2 and the Helmholtz society through Grant No. HIRG-0005. The Ph.D. education of O. Kahl is embedded in the Karlsruhe School of Optics and Photonics (KSOP). G. N. Goltsman acknowledges support by Russian Federation President Grant HШ-1918.2014.2 and Ministry of Education and Science of the Russian Federation Contract No.: RFMEFI58614X0007. A. Korneev acknowledges support by Statement Task No. 3.1846.2014/k. V. Kovalyuk acknowledges support by Statement Task No. 2327. We also acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) and the State of Baden-Württemberg through the DFG-Center for Functional Nanostructures (CFN) within subproject A6.4. We thank S. Kühn and S. Diewald for the help with device fabrication as well as B. Voronov and A. Shishkin for help with NbN thin film deposition and A. Semenov for helpful discussion about the detection mechanism of nanowire SSPD's.

The authors declare no competing financial interests.
 
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  ISSN 0003-6951 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 1211  
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Author Ferrari, S.; Kovalyuk, V.; Vetter, A.; Lee, C.; Rockstuhl, C.; Semenov, A.; Gol'tsman, G.; Pernice, W. url  doi
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  Title Analysis of the detection response of waveguide-integrated superconducting nanowire single-photon detectors at high count rate Type Journal Article
  Year 2019 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 115 Issue 10 Pages 101104  
  Keywords SSPD, SNSPD, waveguide  
  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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  ISSN 0003-6951 ISBN Medium  
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  Notes Approved no  
  Call Number Serial 1185  
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Author Chuprina, I. N.; An, P. P.; Zubkova, E. G.; Kovalyuk, V. V.; Kalachev, A. A.; Gol'tsman, G. N. doi  openurl
  Title Optimisation of spontaneous four-wave mixing in a ring microcavity Type Conference Article
  Year 2017 Publication J. Phys.: Conf. Ser. Abbreviated Journal J. Phys.: Conf. Ser.  
  Volume 47 Issue 10 Pages 887-891  
  Keywords ring microcavity  
  Abstract Abstract. A theory of spontaneous four-wave mixing in a ring microcavity is developed. The rate of emission of biphotons for pulsed and monochromatic pumping with allowance for the disper- sion of group velocities is analytically calculated. In the first case, pulses in the form of an increasing exponential are considered, which are optimal for excitation of an individual resonator mode. The behaviour of the group velocity dispersion as a function of the width and height of the waveguide is studied for a specific case of a ring microcavity made of silicon nitride. The results of the numeri- cal calculation are in good agreement with the experimental data. The ring microcavity is made of two types of waveguides: com- pletely etched and half etched. It is found that the latter allow for better control over the parameters in the manufacturing process, making them more predictable.  
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  Notes Approved no  
  Call Number RPLAB @ kovalyuk @ Serial 1142  
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Author Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Goltsman, G. N.; Verevkin, A. A.; Toropov, A. I.; Mauskopf, P. url  doi
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  Title Concentration dependence of energy relaxation time in AlGaAs/GaAs heterojunctions: direct measurements Type Journal Article
  Year 2011 Publication Semicond. Sci. Technol. Abbreviated Journal Semicond. Sci. Technol.  
  Volume 26 Issue 2 Pages 025013  
  Keywords AlGaAs/GaAs heterojunctions  
  Abstract We present measurements of the energy relaxation time, τε, of electrons in a single heterojunction in a quasi-equilibrium state using microwave time-resolved spectroscopy at 4.2 K. We find the relaxation time has a power-law dependence on the carrier density of the two-dimensional electron gas, τε∝nγs with γ = 0.40 ± 0.02 for values of the carrier density, ns, from 1.6 × 1011 to 6.6 × 1011cm−2. The results are in good agreement with predictions taking into account the scattering of the carriers by both piezoelectric and deformation potential acoustic phonons. We compare these results with indirect measurements of the energy relaxation time from energy loss measurements involving Joule heating of the electron gas.  
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  ISSN 0268-1242 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1215  
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