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Yagubov, P.; Gol'tsman, G.; Voronov, B.; Seidman, L.; Siomash, V.; Cherednichenko, S.; Gershenzon, E. |
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Title ![sorted by Title field, ascending order (up)](img/sort_asc.gif) |
The bandwidth of HEB mixers employing ultrathin NbN films on sapphire substrate |
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Conference Article |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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290-302 |
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NbN HEB mixers, fabrication process |
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We report on some unusual features observed during fabrication of ultrathin NbN films with high Tc. The films were used to fabricate HEB mixers, which were evaluated for IF bandwidth measurements at 140 GHz. Ultrathin films were fabricated using reactive dc magnetron sputtering with a discharge current source. Reproducible parameters of the films are assured keeping constant the difference between the discharge voltage in pure argon, and in a gas mixture, for the same current. A maximum bandwidth of 4 GHz at optimal LO and dc bias was obtained for mixer chip based on NbN film 35 A thick with Tc = 11 K. |
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Charlottesville, Virginia, USA |
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266 |
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Gayduchenko, I. A.; Moskotin, M. V.; Matyushkin, Y. E.; Rybin, M. G.; Obraztsova, E. D.; Ryzhii, V. I.; Goltsman, G. N.; Fedorov, G. E. |
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Title ![sorted by Title field, ascending order (up)](img/sort_asc.gif) |
The detection of sub-terahertz radiation using graphene-layer and graphene-nanoribbon FETs with asymmetric contacts |
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2018 |
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Materials Today: Proc. |
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Materials Today: Proc. |
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5 |
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13 |
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27301-27306 |
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graphene nanoribbons, graphene-nanoribbon, GNR FET, field effect transistor |
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We report on the detection of sub-terahertz radiation using single layer graphene and graphene-nanoribbon FETs with asymmetric contacts (one is the Schottky contact and one – the Ohmic contact). We found that cutting graphene into ribbons a hundred nanometers wide leads to a decrease of the response to sub-THz radiation. We show that suppression of the response in the graphene nanoribbons devices can be explained by unusual properties of the Schottky barrier on graphene-vanadium interface. |
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2214-7853 |
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1316 |
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Iomdina, E. N.; Seliverstov, S.; Sianosyan, A.; Teplyakova, K.; Rusova, A.; Goltsman, G. |
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Title ![sorted by Title field, ascending order (up)](img/sort_asc.gif) |
The prospects of using the radiation for the assessment of corneal and scleral hydration |
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2016 |
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Acta Ophthalmol. |
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Acta Ophthalmol. |
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94 |
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BWO, avalanche transit‐time diode, medicine, biology |
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Purpose
An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells – the cornea and the sclera. THz systems creating images in reflected beams are likely to become ideal instruments of noninvasive testing of corneal and scleral hydration degree as THz radiation is highly sensitive to water content. The paper aims at studying the transmittance and reflectance spectra of the cornea and the sclera of rabbit and human eyes, as well as those of the whole rabbit eye, in the frequency range of 0.13–0.32 THz.
Methods
The experiments were carried out on 3 corneas and 3 rabbit scleras, 2 whole rabbit eyes, and 3 human healthy adult scleras using a specially developed THz system based on reliable and easy‐to‐use continuous wave sources: a backward‐wave oscillator and an avalanche transit‐time diode.
Results
The transmittance spectra of the cornea and the sclera and the dependence of the reflection coefficient of these tissues in THz range on water percentage content were determined. Comparison of the rabbit cornea hydrated from 73.2% to 76.3% concentration by mass demonstrated an approximately linear relationship between THz reflectivity and water concentration. The decrease of free water concentration by 1% leads to a drop of the reflectance coefficient by 13%. The parameters studied displayed noticeable differences between the sclera and the cornea of rabbits and between rabbit sclera and human sclera.
Conclusions
Preliminary results demonstrate that the proposed technique, based on continuous THz radiation, may be used to create a device for noninvasive testing of corneal and scleral hydration, which has good potential of wide‐scale practical application.
The work was supported by the Russian Foundation of Basic Research (grant No.15‐29‐03843) |
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1755375X |
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1333 |
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Meledin, D.; Tong, C. Y.-E.; Blundell, R.; Kaurova, N.; Smirnov, K.; Voronov, B.; Gol'tsman, G. |
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Title ![sorted by Title field, ascending order (up)](img/sort_asc.gif) |
The sensitivity and IF bandwidth of waveguide NbN hot electron bolometer mixers on MgO buffer layers over crystalline quartz |
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Conference Article |
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2002 |
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Proc. 13th Int. Symp. Space Terahertz Technol. |
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Proc. 13th Int. Symp. Space Terahertz Technol. |
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65-72 |
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waveguide NbN HEB mixers |
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We have developed and characterized waveguide phonon-cooled NbN Hot Electron Bolometer (FMB) mixers fabricated from a 3-4 nm thick NbN film deposited on a 200nm thick MgO buffer layer over crystalline quartz. Double side band receiver noise temperatures of 900-1050 K at 1.035 THz, and 1300-1400 K at 1.26 THz have been measured at an intermediate frequency of 1.5 GHz. The intermediate frequency bandwidth, measured at 0.8 THz LO frequency, is 3.2 GHz at the optimal bias point for low noise receiver operation. |
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Cambridge, MA, USA |
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Harvard university |
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326 |
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Author |
Gol’tsman, G. N. |
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Title ![sorted by Title field, ascending order (up)](img/sort_asc.gif) |
The “Millimetron” project, a future space telescope mission |
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2007 |
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Proc. 18th Int. Symp. Space Terahertz Technol. |
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Proc. 18th Int. Symp. Space Terahertz Technol. |
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255 |
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Millimetron space observatory, VLBI |
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The goal of the Millimetron project is to develop a space observatory operating in the millimeter, sub-millimeter and infrared wavelength ranges using a 12-m actively cooled telescope in a single-dish mode and as an interferometer with the space-ground and space-space baselines (the later after the launch of the second identical space telescope). The Millimetron’s main reflector and other optics will be cooled down to 4K thus enabling astronomical observations with super high sensitivity in MM and subMM (down to nanoJansky level). Heterodyne observations in an interferometer mode at frequencies 0.1-1 THz will provide super high angular resolution. The main instruments, planned to be installed are wide-range imaging arrays, radiometers with spectrometers and polarimeters, VLBI heterodyne receivers, and Mikelson type interferometer devices. Wide-range MM and subMM imaging arrays and spectrometers will be based on a superconducting hot electron direct detectors with Andreev mirrors operating at 0.1 K. Such detectors are the best candidates to reach the noise equivalent power level of 10 -19 -10 -20 W/√Hz. Heterodyne receivers will be both SIS based superconducting integrated receiver with flux-flow oscillator as LO (0.1-0.9 THz range) and HEB based receivers using multiplied Gunn oscillator as LO for 1-2 THz range and quantum cascade lasers as LO for 2-5 THz range. For observations in middle IR region there will be installed large arrays of superconducting single photon detectors, providing imaging with very high dynamic range and ultimate sensitivity. |
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1422 |
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