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Author Yang, J. K. W.; Kerman, A. J.; Dauler, E. A.; Anant, V.; Rosfjord, K. M.; Berggren, K. K.
Title Modeling the electrical and thermal response of superconducting nanowire single-photon detectors Type Journal Article
Year 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal (up)
Volume 17 Issue 2 Pages 581 - 585
Keywords SSPD, modeling
Abstract We modeled the response of superconducting nanowire single-photon detectors during a photodetection event, taking into consideration only the thermal and electrical properties of a superconducting NbN nanowire on a sapphire substrate. Our calculations suggest that heating which occurs after the formation of a photo-induced resistive barrier is responsible for the generation of a measurable voltage pulse. We compared this numerical result with experimental data of a voltage pulse from a slow device, i.e. large kinetic inductance, and obtained a good fit. Using this electro-thermal model, we estimated the temperature rise and the resistance buildup in the nanowire, and the return current at which the nanowire becomes superconducting again. We also show that the reset time of these photodetectors can be decreased by the addition of a series resistance and provide supporting experimental data. Finally we present preliminary results on a detector latching behavior that can also be explained using the electro-thermal model.
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Call Number Serial 625
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Author Xiaolong Hu; Holzwarth, C.W.; Masciarelli, D.; Dauler, E.A.; Berggren, K.K.
Title Efficiently coupling light to superconducting nanowire single-photon detectors Type Journal Article
Year 2009 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal (up)
Volume 19 Issue 3 Pages 336-340
Keywords optical antennas; SNSPD
Abstract We designed superconducting nanowire single-photon detectors (SNSPDs) integrated with silver optical antennae for free-space coupling and a dielectric waveguide for fiber coupling. According to our finite-element simulation, (1) for the free-space coupling, the absorptance of the NbN nanowire for TM-polarized photons at the wavelength of 1550 nm can be as high as 96% by adding silver optical antennae; (2) for the fiber coupling, the absorptance of the NbN nanowire for TE-like-polarized photons can reach 76% including coupling efficiency at the wavelength of 1550 nm by adding a silicon nitride waveguide and an inverse-taper coupler.
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Call Number RPLAB @ gujma @ Serial 647
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Author Yang, J.K.W.; Kerman, A.J.; Dauler, E.A.; Cord, B.; Anant, V.; Molnar, R.J.; Berggren, K.K.
Title Suppressed critical current in superconducting nanowire single-photon detectors with high fill-factors Type Journal Article
Year 2009 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal (up)
Volume 19 Issue 3 Pages 318-322
Keywords SNSPD
Abstract In this work we present a new fabrication process that enabled the fabrication of superconducting nanowire single photon detectors SNSPD with fill-factors as high as 88% with gaps between nanowires as small as 12 nm. This fabrication process combined high-resolution electron-beam lithography with photolithography. Although this work was motivated by the potential of increased detection efficiency with higher fill-factor devices, test results showed an unexpected systematic suppression in device critical currents with increasing fill-factor.
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Call Number RPLAB @ gujma @ Serial 677
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Author Kerman, A. J.; Dauler, E. A.; Yang, J. K. W.; Rosfjord, K. M.; Anant, V.; Berggren, K. K.; Gol’tsman, G. N.; Voronov, B. M.
Title Constriction-limited detection efficiency of superconducting nanowire single-photon detectors Type Journal Article
Year 2007 Publication Appl. Phys. Lett. Abbreviated Journal (up) Appl. Phys. Lett.
Volume 90 Issue 10 Pages 101110 (1 to 3)
Keywords SSPD, SNSPD
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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ISSN 0003-6951 ISBN Medium
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Call Number Serial 1433
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Author Kerman, A. J.; Dauler, E. A.; Keicher, W. E.; Yang, J. K. W.; Berggren, K. K.; Gol’tsman, G.; Voronov, B.
Title Kinetic-inductance-limited reset time of superconducting nanowire photon counters Type Journal Article
Year 2006 Publication Appl. Phys. Lett. Abbreviated Journal (up) Appl. Phys. Lett.
Volume 88 Issue 11 Pages 111116 (1 to 3)
Keywords NbN SSPD, SNSPD
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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ISSN 0003-6951 ISBN Medium
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Notes Approved no
Call Number Serial 1453
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