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Author Edward Tong, C.-Y.; Loudkov, Denis N.; Paine, Scott N.; Marrone, Dan P.; Blundell, Raymond url  openurl
  Title Vector measurement of the beam pattern of a 1.5 THz superconducting HEB receiver Type Conference Article
  Year 2005 Publication Proc. 16th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 16th Int. Symp. Space Terahertz Technol.  
  Volume Issue (down) Pages 453-456  
  Keywords NbTiN HEB mixers  
  Abstract Near-field vector beam pattern of the 1.5 THz superconducting Hot Electron Bolometer (HEB) receiver currently in operation in Northern Chile has been performed in our laboratory. Using an open waveguide probe, we have mapped both the amplitude and phase of the beam emerging from our 1.5 THz HEB receiver package, across a number of planes along the line of propagation of the radio-beam. With an integration time of about 100 ms per point, a signal-to-noise ratio of about 25 dB was achieved for a beam waist of 3.5 mm. These measurements have proved to be invaluable in achieving good alignment between the cryostat housing the HEB mixer and the remainder of the receiver and telescope optics. The accuracy of our beam measurement is estimated to be ±0.2 mm in position and ±5 arc minutes in angular displacement.  
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  Notes Approved no  
  Call Number Serial 1474  
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Author Darula, Marian; Semenov, Alex D.; Hübers, Heinz-Wilhelm; Schubert, Josef url  openurl
  Title Quasioptical high-Tc superconductor Josephson mixer at terahertz frequencies Type Abstract
  Year 2000 Publication Proc. 11th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 11th Int. Symp. Space Terahertz Technol.  
  Volume Issue (down) Pages 515  
  Keywords HTS Josephson mixers  
  Abstract Mixers based on Josephson junctions from conventional superconductor materials have demonstrated excellent performance at subgap frequencies. The advantages of Josephson mixers are low optimal power of the local oscillator and large intermediate frequency bandwidth but their noise temperature increases dramatically at frequencies corresponding to the energy gap of the superconductor, which is typically below 1 THz for widely used materials. The large energy gap of oxide superconductors makes them promising candidates for development of terahertz Josephson mixers. Here we report on experimental study of the quasioptical mixer utilizing bicrystal Josephson junction from high-transition-temperature YBa 2 Cu 3 O 7-δ film. Junctions with a width of 2 µm were fabricated from 100 nm thick laser ablated films on bicrystal MgO substrates and had the and the J C R n product of about 2 mV at 4.2 K. The planar complementary logarithmic spiral antenna incorporated into co-planar waveguide was patterned from 200 nm thick gold film thermally evaporated in situ on top of the YBa 2 Cu 3 O 7-δ film. The mixer chip was clamped to the extended hemispherical silicon lens. Performance of the mixer was investigated at 4.5 K bath temperature. We used FIR laser as a local oscillator at frequencies 0.698 and 2.52 THz. System noise temperature (DSB) was determined from Y-factor measured with 300 K and 77 K loads. At 0.698 THz the lowest noise temperature 1750 K was observed when the mixer was biased with the fixed current to the region in the vicinity of either the first Shapiro step or the critical current. Between these two bias points the noise temperature increased to ≈ 20000 K. As function of the local oscillator power the noise temperature reached the minimum when the critical current was suppressed to the half of its equilibrium value. Power of the local oscillator absorbed by the mixer at optimal operation was of the order 100 nW. The present design of our antenna limits the upper operation frequency to the value of 1.8 THz. Nevertheless, we clearly observed Shapiro steps at the frequency 2.52 THz. Bearing in mind an improved design of the antenna, we estimate the 3000 K DSB noise temperature at this frequency.  
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  Notes Approved no  
  Call Number Serial 1555  
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Author Ekström, H.; Karasik, B.; Kollberg, E.; Yngvesson, K. S. url  openurl
  Title Investigation of a superconducting hot electron mixer Type Conference Article
  Year 1994 Publication Proc. 5th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 5th Int. Symp. Space Terahertz Technol.  
  Volume Issue (down) Pages 169-188  
  Keywords HEB mixers  
  Abstract Mixing at 20 GHz in niobium superconducting thin film strips in the resistive state is studied. Experiments give evidence that electron-heating is the main cause of the non linear phenomena. The requirements on the mode of operation and on the film parameters for small conversion loss and the possibility of conversion gain are discussed. Measurements indicate a minimum intrinsic conversion loss around 1 dB with a sharp drop for the lowest voltage bias-points, and a DSB mixer noise temperature between 100 and 450 K at 20 GHz. The device output noise temperature at the mixer operating point can be as low as 30-50 K. A simple theory is presented, which is based on the assumption that the small signal resistance is linearly dependent on power. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies.  
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  Notes Approved no  
  Call Number Serial 1642  
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Author Elantev, Andrey I.; Karasik, Boris S. url  openurl
  Title Noise temperature of a superconducting hot-electron mixer Type Conference Article
  Year 1994 Publication Proc. 5th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 5th Int. Symp. Space Terahertz Technol.  
  Volume Issue (down) Pages 225  
  Keywords HEB mixers  
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  Notes Approved no  
  Call Number Serial 1645  
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Author Sergeev, A. V.; Livanov, D. V. url  doi
openurl 
  Title Phonon renormalization of thermoelectric power of high-Tc materials Type Conference Article
  Year 1993 Publication Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences Abbreviated Journal Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences  
  Volume 112 Issue (down) Pages 204-205  
  Keywords HTS, YBCO  
  Abstract Renormalization of thermoelectric power due to Nielsen — Taylor effect (interference between electron-phonon and electron- impurity interactions) is used for the explanation of the temperature dependence and sign of the thermopower in high-Tc materials. In the framework of the model the negative sign of TEP of untwinned YBa2Cu3O7−x crystal in a-direction observed by Howson et. al. is connected to the strong hole scattering via O-vacancies in chains.  
  Address  
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  Publisher Place of Publication Editor Meissner, M.; Pohl, R. O.  
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  Area Expedition Conference Seventh International Conference, Cornell University, Ithaca, New York, August 3-7, 1992  
  Notes Approved no  
  Call Number Serial 1664  
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Author Sergeev, A.; Karasik, B. S.; Ptitsina, N. G.; Chulkova, G. M.; Il'in, K. S.; Gershenzon, E. M. url  doi
openurl 
  Title Electron–phonon interaction in disordered conductors Type Journal Article
  Year 1999 Publication Phys. Rev. B Condens. Matter Abbreviated Journal Phys. Rev. B Condens. Matter  
  Volume 263-264 Issue (down) Pages 190-192  
  Keywords disordered conductors, electron-phonon interaction  
  Abstract The electron–phonon interaction is strongly modified in conductors with a small value of the electron mean free path (impure metals, thin films). As a result, the temperature dependencies of both the inelastic electron scattering rate and resistivity differ significantly from those for pure bulk materials. Recent complex measurements have shown that modified dependencies are well described at K by the electron interaction with transverse phonons. At helium temperatures, available data are conflicting, and cannot be described by an universal model.  
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  ISSN 0921-4526 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1765  
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Author Gershenzon, E. M.; Gurvich, Y. A.; Orlova, S. L.; Ptitsina, N. G. url  openurl
  Title Scattering of electrons by charged impurities in Ge under cyclotron resonance conditions Type Journal Article
  Year 1976 Publication Presumably: Sov. Phys. Semicond. | Физика и техника полупроводников Abbreviated Journal Presumably: Sov. Phys. Semicond. | Физика и техника полупроводников  
  Volume 10 Issue (down) Pages 1379-1383  
  Keywords Ge, cyclotron resonance, charged impurities,  
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  Notes Approved no  
  Call Number Serial 1772  
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Author Bondarenko, O. I.; Gershenzon, E. M.; Gurvich, Y. A.; Orlova, S. L.; Ptitsina, N. G. url  openurl
  Title Measurement of the width of the cyclotron resonance line of n-type Ge in quantizing magnetic fields Type Journal Article
  Year 1972 Publication Presumably: Sov. Phys. Semicond. | Физика и техника полупроводников Abbreviated Journal Presumably: Sov. Phys. Semicond. | Физика и техника полупроводников  
  Volume 6 Issue (down) Pages 362-363  
  Keywords Ge, cyclotron resonance, quantizing magnetic fields  
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  Notes Approved no  
  Call Number Serial 1774  
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Author Dube, I.; Jiménez, D.; Fedorov, G.; Boyd, A.; Gayduchenko, I.; Paranjape, M.; Barbara, P. url  doi
openurl 
  Title Understanding the electrical response and sensing mechanism of carbon-nanotube-based gas sensors Type Journal Article
  Year 2015 Publication Carbon Abbreviated Journal Carbon  
  Volume 87 Issue (down) Pages 330-337  
  Keywords carbon nanotubes, CNT detectors, field effect transistors, FET  
  Abstract Gas sensors based on carbon nanotube field effect transistors (CNFETs) have outstanding sensitivity compared to existing technologies. However, the lack of understanding of the sensing mechanism has greatly hindered progress on calibration standards and customization of these nano-sensors. Calibration requires identifying fundamental transistor parameters and establishing how they vary in the presence of a gas. This work focuses on modeling the electrical response of CNTFETs in the presence of oxidizing (NO2) and reducing (NH3) gases and determining how the transistor characteristics are affected by gas-induced changes of contact properties, such as the Schottky barrier height and width, and by the doping level of the nanotube. From the theoretical fits of the experimental transfer characteristics at different concentrations of NO2 and NH3, we find that the CNTFET response can be modeled by introducing changes in the Schottky barrier height. These changes are directly related to the changes in the metal work function of the electrodes that we determine experimentally, independently, with a Kelvin probe. Our analysis yields a direct correlation between the ON – current and the changes in the electrode metal work function. Doping due to molecules adsorbed at the carbon-nanotube/metal interface also affects the transfer characteristics.  
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  ISSN 0008-6223 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1778  
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Author Korneev, A. A. url  doi
openurl 
  Title Superconducting NbN microstrip single-photon detectors Type Abstract
  Year 2021 Publication Proc. Quantum Optics and Photon Counting Abbreviated Journal Proc. Quantum Optics and Photon Counting  
  Volume 11771 Issue (down) Pages  
  Keywords NbN SSPD, SNSPD  
  Abstract Superconducting Single-Photon Detectors (SSPD) invented two decades ago have evolved to a mature technology and have become devices of choice in the advanced applications of quantum optics, such as quantum cryptography and optical quantum computing. In these applications SSPDs are coupled to single-mode fibers and feature almost unity detection efficiency, negligible dark counts, picosecond timing jitter and MHz photon count rate. Meanwhile, there are great many applications requiring coupling to multi-mode fibers or free space. ‘Classical’ SSPDs with 100-nm-wide superconducting strip and covering area of about 100 µm2 are not suitable for further scaling due to degradation of performance and low fabrication yield. Recently we have demonstrated single-photon counting in micron-wide superconducting bridges and strips. Here we present our approach to the realization of practical photon-counting detectors of large enough area to be efficiently coupled to multi-mode fibers or free space. The detector is either a meander or a spiral of 1-µm-wide strip covering an area of 50x50 µm2. Being operated at 1.7K temperature it demonstrates the saturated detection efficiency (i.e. limited by the absorption in the detector) up to 1550 nm wavelength, about 10 ns dead time and timing jitter in range 50-100 ps.  
  Address  
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  Publisher SPIE Place of Publication Editor Prochazka, I.; Štefaňák, M.; Sobolewski, R.; Gábris, A.  
  Language Summary Language Original Title  
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  Area Expedition Conference Quantum Optics and Photon Counting; SPIE Optics + Optoelectronics, 2021, Online Only  
  Notes Approved no  
  Call Number Serial 1784  
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