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Zhang W, Li N, Jiang L, Ren Y, Yao Q-J, Lin Z-H, et al. Dependence of noise temperature of quasi-optical superconducting hot-electron bolometer mixers on bath temperature and optical-axis displacement. In: Zhang C, Zhang X-C, editors. Proc. SPIE. Vol 6840. Spie; 2008. 684007 (1 to 8).
Abstract: It is known that the increase of bath temperature results in the decrease of critical current of superconducting hot-electron bolometer (HEB) mixers owing to the depression of superconductivity, thus leading to the degradation of the mixer’s sensitivity. Here we report our study on the effect of bath temperature on the heterodyne mixing performance of quasi-optical superconducting NbN HEB mixers incorporated with a two-arm log-spiral antenna. The correlation between the bath temperature, critical current, LO power requirement and noise temperature is investigated at 0.5 THz. Furthermore, the heterodyne mixing performance of quasi-optical superconducting NbN HEB mixers is examined while there is an optical-axis displacement between the center of the extended hemispherical silicon lens and the superconducting NbN HEB device, which is placed on the back of the lens. Detailed experimental results and analysis are presented.
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Wild W, Baryshev A, de Graauw T, Kardashev N, Likhachev S, Goltsman G, et al. Instrumentation for Millimetron – a large space antenna for THz astronomy. In: Proc. 19th Int. Symp. Space Terahertz Technol.; 2008. p. 186–91.
Abstract: Millimetron is a Russian-led 12m diameter submillimeter and far-infrared space observatory which is included in the Space Plan of the Russian Federation and funded for launch after 2015. With its large collecting area and state-of-the-art receivers, it will enable unique science and allow at least one order of magnitude improvement with respect to the Herschel Space Observatory. Millimetron is currently in a conceptual design phase carried out by the Astro Space Center in Moscow and SRON Netherlands Institute for Space Research. It will use a passively cooled deployable antenna with a high-precision central 3.5m diameter mirror and high- precision antenna petals. The antenna is specified for observations up to ~2 THz over the whole 12m diameter, and to higher frequencies using the central 3.5m solid mirror. Millimetron will be operated in two basic observing modes: as a single-dish observatory, and as an element of a ground-space VLBI system. As single-dish, angular resolutions on the order of 3 to 12 arcsec will be achieved and spectral resolutions of up to 10 6 employing heterodyne techniques. As VLBI antenna, the chosen elliptical orbit will provide extremely large VLBI baselines resulting in micro-arcsec angular resolution. The scientific payload will consist of heterodyne and direct detection instruments covering the most important sub-/millimeter spectral regions (including some ALMA bands) and will build on the Herschel and ALMA heritage.
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Wei J, Olaya D, Karasik BS, Pereverzev SV, Sergeev AV, Gershenson ME. Ultrasensitive hot-electron nanobolometers for terahertz astrophysics. Nature Nanotech. 2008;3(8):496–500.
Abstract: The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers – devices for measuring the energy of electromagnetic radiation—with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment;
second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron–phonon interactions, becomes very small at low temperatures (10-16 WK-1 at 40 mK). These devices, with a heat capacity of 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting.
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Tretyakov IV, Ryabchun SA, Maslennikov SN, Finkel MI, Kaurova NS, Seleznev VA, et al. NbN HEB mixer: fabrication, noise temperature reduction and characterization. In: Proc. Basic problems of superconductivity. Moscow-Zvenigorod; 2008.
Abstract: We demonstrate that in the terahertz region superconducting hot-electron mixers offer the lowest noise temperature, opening the possibility of using HTS's in the future to fabricate these devices. Specifically, a noise temperature of 950 K was measured for the receiver operating at 2.5 THz with a NbN HEB mixer, and a gain bandwidth of 6 GHz was measured at 300 GHz near Tc for the same mixer.
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Tikhonov VV, Polyakova ON, Gol’tsman GN, Dzardanov AL, Boyarskiy DA. Determination of dielectric properties of ore minerals in the microwave band. Radiophys Quant Electron. 2008;51(12):966–74.
Abstract: We consider a method for determining the complex dielectric permittivity of ore and nonmetal minerals in the microwave band of electromagnetic radiation. The results of measuring the reflectivity and transmittivity of chalcopyrite, magnetite, sphalerite, and labradorite samples in the frequency range 77–300 GHz are presented. A method for calculation of the complex dielectric permittivity of minerals on the basis of the obtained experimental data is proposed. The approximation formulas for calculation of the complex dielectric permittivity of the studied minerals are given.
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Thijs de Graauw, Nick Whyborn, Frank Helmich, Pieter Dieleman, Peter Roelfsema, Emmanuel Caux, et al. The Herschel-heterodyne instrument for the far-infrared (HIFI): instrument and pre-launch testing. In: Proc. SPIE. Vol 7010.; 2008. 701004.
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Tarkhov M, Claudon J, Poizat JP, Korneev A, Divochiy A, Minaeva O, et al. Ultrafast reset time of superconducting single photon detectors. Appl Phys Lett. 2008;92(24):241112 (1 to 3).
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Tang L, Kocabas SE, Latif S, Okyay AK, Ly-Gagnon D-S, Saraswat KC, et al. Nanometre-scale germanium photodetector enhanced by a near-infrared dipole antenna. Nature Photonics. 2008;2:226–9.
Abstract: A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise. A photodetector can be made smaller by using a subwavelength active region; however, this can result in very low responsivity because of the diffraction limit of the light. Here we exploit the idea of a half-wave Hertz dipole antenna (length approx 380 nm) from radio waves, but at near-infrared wavelengths (length approx 1.3 microm), to concentrate radiation into a nanometre-scale germanium photodetector. This gives a polarization contrast of a factor of 20 in the resulting photocurrent in the subwavelength germanium element, which has an active volume of 0.00072 microm3, a size that is two orders of magnitude smaller than previously demonstrated detectors at such wavelengths.
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Steier WH, Oh MC, Zhang C, Zhang H, Szep A, Fetterman HR, et al. Electro-optic polymers and applications in next generation phase array antennas.; 2008.
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Smirnov KV, Vachtomin YB, Ozhegov RV, Pentin IV, Slivinskaya EV, Korneev AA, et al. Fiber coupled single photon receivers based on superconducting detectors for quantum communications and quantum cryptography. In: Tománek P, Senderáková D, Hrabovský M, editors. Proc. SPIE. Vol 7138. Spie; 2008. 713827 (1 to 6).
Abstract: At present superconducting detectors become increasingly attractive for various practical applications. In this paper we present results on the depelopment of fiber coupled receiver systems for the registration of IR single photons, optimized for telecommunication and quantum-cryptography. These receiver systems were developed on the basis of superconducting single photon detectors (SSPD) of VIS and IR wavelength ranges. The core of the SSPD is a narrow ( 100 nm) and long ( 0,5 mm) strip in the form of a meander which is patterned from a 4-nm-thick NbN film (TC=10-11 K, jC= 5-7•106 A/cm2); the sensitive area dimensions are 10×10 μm2. The main problem to be solved while the receiver system development was optical coupling of a single-mode fiber (9 microns in diameter) with the SSPD sensitive area. Characteristics of the developed system at the optical input are as follows: quantum efficiency >10 % (at 1.3 μm), >4 % (at 1.55 μm); dark counts rate ≤1 s-1; duration of voltage pulse ≤5 ns; jitter ≤40 ps. The receiver systems have either one or two identical channels (for the case of carrying out correlation measurements) and are made as an insert in a helium storage Dewar.
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