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Author Lobanov, Y.; Tong, C.; Blundell, R.; Gol'tsman, G.
Title A study of direct detection effect on the linearity of hot electron bolometer mixers Type Conference Article
Year (up) 2009 Publication Proc. 20th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 20th ISSTT
Volume Issue Pages 282-287
Keywords HEB mixer, direct detection effect
Abstract We have performed a study of how direct detection affects the linearity and hence the calibration of an HEB mixer. Two types of waveguide HEB devices have been used: a 0.8 THz HEB mixer and a 1.0 THz HEB mixer which is ~5 times smaller than the former. Two independent experimental approaches were used. In the ΔG/G method, the conversion gain of the HEB mixer is first measured as a function of the bias current for a number of bias voltages. At each bias setting, we carefully measure the change in the operating current when the input loads are switched. From the measured data, we can derive the expected difference in gain between the hot and cold loads. In the second method (injection method [1]), the linearity of the HEB mixer is independently measured by injecting a modulated signal for different input load temperatures. The results of both approaches confirm that there is gain compression in the operation of HEB mixers. Based on the results of our measurements, we discuss the impact of direct detection effects on the operation of HEB mixers.
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Call Number RPLAB @ gujma @ Serial 724
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Author Marksteiner, M.; Divochiy, A.; Sclafani, M.; Haslinger, P.; Ulbricht, H.; Korneev, A.; Semenov, A.; Gol'tsman, G.; Arndt, M.
Title A superconducting NbN detector for neutral nanoparticles Type Journal Article
Year (up) 2009 Publication Nanotechnol. Abbreviated Journal Nanotechnol.
Volume 20 Issue 45 Pages 455501
Keywords SSPD; SNSPD; *Electric Conductivity; Microscopy, Electron, Scanning; Nanoparticles/*chemistry/ultrastructure; Nanotechnology/*methods; *Photons
Abstract We present a proof-of-principle study of superconducting single photon detectors (SSPD) for the detection of individual neutral molecules/nanoparticles at low energies. The new detector is applied to characterize a laser desorption source for biomolecules and allows retrieval of the arrival time distribution of a pulsed molecular beam containing the amino acid tryptophan, the polypeptide gramicidin as well as insulin, myoglobin and hemoglobin. We discuss the experimental evidence that the detector is actually sensitive to isolated neutral particles.
Address University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria. markus.arndt@univie.ac.at
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ISSN 0957-4484 ISBN Medium
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Notes PMID:19822928 Approved no
Call Number Serial 1239
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Author Lobanov, Y. V.; Tong, Cheuk-Yu E.; Hedden, A. S.; Blundell, R.; Gol'tsman, G. N.
Title Microwave-assisted슠measurement슠of the슠frequency슠response슠of슠terahertz슠HEB슠mixers슠with a슠fourier슠transform슠spectrometer Type Conference Article
Year (up) 2010 Publication 21st International Symposium on Space Terahertz Technology Abbreviated Journal 21st ISSTT
Volume Issue Pages 420-423
Keywords HEB mixer
Abstract We describe a novel method of operation of the HEB direct detector for use with a Fourier Transform Spectrometer. Instead of elevating the bath temperature, we have measured the RF response of waveguide HEB mixers by applying microwave radiation to select appropriate bias conditions. In our experiment, a microwave signal is injected into the HEB mixer via its IF port. By choosing an appropriate injection level, the device can be operated close to the desired operating point. Furthermore, we have shown that both thermal biasing and microwave injection can reproduce the same spectral response of the HEB mixer. However, with the use of microwave injection, there is no need to wait for the mixer to reach thermal equilibrium, so characterisation can be done in less time. Also, the liquid helium consumption for our wet cryostat is also reduced. We have demonstrated that the signalto-noise ratio of the FTS measurements can be improved with microwave injection.
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Call Number RPLAB @ gujma @ Serial 725
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Author Smirnov, K. V.; Vakhtomin, Yu. B.; Divochiy, A. V.; Ozhegov, R. V.; Pentin, I. V.; Gol'tsman, G. N.
Title Infrared and terahertz detectors on basis of superconducting nanostructures Type Conference Article
Year (up) 2010 Publication Microwave and Telecom. Technol. (CriMiCo), 20th Int. Crimean Conf. Abbreviated Journal
Volume Issue Pages 823-824
Keywords SSPD, SNSPD, HEB
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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Publisher Place of Publication Editor IEEE
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Notes Approved no
Call Number RPLAB @ sasha @ smirnov2010infrared Serial 1025
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Author Beck, M.; Klammer, M.; Lang, S.; Leiderer, P.; Kabanov, V. V.; Gol'tsman, G. N.; Demsar, J.
Title Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy Type Journal Article
Year (up) 2011 Publication Phys. Rev. Lett. Abbreviated Journal Phys. Rev. Lett.
Volume 107 Issue 17 Pages 4
Keywords NbN thin film, energy gap dynamics
Abstract Using time-domain terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor 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 bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, λ=1.1±0.1, which is in excellent agreement with theoretical estimates.
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Call Number RPLAB @ gujma @ Serial 641
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