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Risacher, C.; Meledin, D.; Belitsky, V.; Bergman, P. |
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First 1.3 THz observations at the APEX telescope |
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2009 |
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Proc. 20th Int. Symp. Space Terahertz Technol. |
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54-61 |
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balanced HEB mixer noise temperature APEX telescope stability Allan variance aperture efficiency |
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The Atacama Pathfinder EXperiment (APEX) 12m telescope is operating on the Llano Chajnantor, Chile, since 2003 and a set of state of the art sub-millimeter receivers have been installed for frequencies spanning from 150 GHz to 1500 GHz. In 2008, a balanced 1.3 THz Hot Electron Bolometer (HEB) receiver was installed for the atmospheric window 1250-1380 GHz. This instrument is part of a 4-channel receiver cryostat with the other channels being 211-275 GHz, 275-370 GHz and 380-500 GHz Sideband Separating (SSB) SIS receivers. This paper presents the first observations obtained so far with the 1.3 THz band during its first months of operation. The sky measurements were taken during opportunistic commissioning and science verification phases, when the weather conditions were sufficiently good with a Precipitable Water Vapor (PWV) below 0.25 mm, which was the case only a few nights during these months. We present the first observations of the molecular transition CO J=(11-10) line on different sources such as Orion-FIR4, CW-Leo and SgrB2(M). We describe the many challenges and difficulties encountered for achieving successful THz observations from a large sub-millimeter ground-based telescope. |
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619 |
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Venkatasubramanian, Chandrasekaran; Cabarcos, Orlando M.; Allara, David L. Horn, Mark W.; Ashok, S. |
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Correlation of temperature response and structure of annealed VOx thin films for IR detector applications |
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2009 |
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J. Vac. Sci. Technol. A |
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27 |
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4 |
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6 |
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Annealing |
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The effects of thermal annealing on vanadium oxide (VOx) thin films prepared by pulsed-dc magnetron sputtering were studied to explore methods of improving the efficiency of uncooled IR imaging microbolometers, particularly with respect to maximizing the temperature coefficients of resistance (TCR) (typically ~2%) while minimizing resistivity values (typically 0.05–5 Ω cm). Since high TCR values are usually associated with high resistivities, the experiments were designed to find processing conditions that provide an optimal balance in these properties and to then determine the underlying structural correlations which would enable rational design of thin films for this specific application. VOx films of different compositions were deposited by pulsed-dc reactive sputtering from a vanadium target at different oxygen flow rates. The deposited films were further modified by annealing in inert (nitrogen) and oxidizing (oxygen) atmospheres at four different temperatures for 10, 20, or 30 min at a time. The resistivities of the as-deposited films ranged from 0.2 to 13 Ω cm and the TCR values varied from –1.6% to –2.2%. Depending on the exact annealing conditions, several orders of magnitude change in resistance and significant variations in TCR were observed. Optimal results were obtained with annealing in a nitrogen atmosphere. Structural characterization by x-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and Raman spectroscopy indicated changes in the film crystallinity and phase for annealing conditions over 300 °C with the onset and extent of the changes dependent on which annealing atmosphere was used. |
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Annealing |
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RPLAB @ gujma @ |
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690 |
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Anosov, A. A.; Barabanenkov, Yu. N.; Kazanskii, A. S.; Less, Yu. A.; Sharakshane, A. S. |
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The inverse problem of acoustothermography with correlation reception of thermal acoustic radiation |
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2009 |
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Acoust. Phys. |
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55 |
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1 |
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114-119 |
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acoustic thermography, acoustothermography |
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For the one-dimensional inverse problem of acoustothermography with correlation reception of thermal acoustic radiation, an integral equation is presented and experimentally verified. A method of solving the inverse problem is proposed. The method is based on combining the correlation functions of thermal acoustic radiation that were obtained for different distances between the receivers. |
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1131 |
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Cao, Q.; Yoon, S. F.; Tong, C. Z.; Ngo, C. Y.; Liu, C. Y.; Wang, R.; Zhao, H. X. |
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Two-state competition in 1.3 μm multilayer InAs/InGaAs quantum dot lasers |
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2009 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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95 |
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19 |
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3 |
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2DEG |
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The competition of ground state (GS) and excited state (ES) is investigated from the as-grown and thermally annealed 1.3 μm ten-layer p-doped InAs/GaAs quantum dot (QD) lasers. The modal gain competition between GS and ES are measured and analyzed around the ES threshold characteristics. Our results show that two-state competition is more significant in devices with short cavity length operating at high temperature. By comparing the as-grown and annealed devices, we demonstrate enhanced GS and suppressed ES lasing from the QD laser annealed at 600 °C for 15 s. |
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RPLAB @ gujma @ |
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673 |
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Kern, Pierre; Le Coärer, Etienne; Benech, Pierre |
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On-chip spectro-detection for fully integrated coherent beam combiners |
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2009 |
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Optics Express |
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Opt.Express |
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17 |
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3 |
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1976-1987 |
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This paper presents how photonics associated with new arising detection technologies is able to provide fully integrated instrument for coherent beam combination applied to astrophysical interferometry. The feasibility and operation of on-chip coherent beam combiners has been already demonstrated using various interferometric combination schemes. More recently we proposed a new detection principle aimed at directly sampling and extracting the spectral information of an input signal together with its flux level measurement. The so-called SWIFTS demonstrated concept that stands for Stationary-Wave Integrated Fourier Transform Spectrometer, provides full spectral and spatial information recorded simultaneously thanks to a motionless detecting device. Due to some newly available detection principles considered for the implementation of the SWIFTS concept, some technologies can even provide photo-counting operation that brought a significant extension of the interferometry domain of investigation in astrophysics. The proposed concept is applicable to most of the interferometric instrumental modes including fringe tracking, fast and sensitive detection, Fourier spectral reconstruction and also to manage a large number of incoming beams. The paper presents three practical implementations, two dealing with pair-wise integrated optics beam combinations and the third one with an all-in-one 8 beam combination. In all cases the principles turned into a pair wise baseline coding after proper data processing. |
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650 |
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Karpowicz, Nicholas; Lu, Xiaofei; Zhang, X.-C. |
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Terahertz gas photonics |
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2009 |
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J. Modern Opt. |
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56 |
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10 |
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1137-1150 |
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The underlying physics of the generation and detection of terahertz (THz) waves in gases are described. The THz wave generation process takes place in two steps: asymmetric gas ionization by two-frequency laser fields, followed by interaction of the ionized electron wave packets with the surrounding medium, producing an intense ‘echo' with tunable spectral content. In order to clarify the physical picture at the moment of ionization, the laser–atom interaction is treated through solution of the time-dependent Schrödinger equation, yielding an ab initio understanding of the release of the electron wave packets. The second step, where the electrons interact with the surrounding plasma is treated analytically. The resulting pressure dependence of the THz radiation is explored in detail. The THz wave detection process is shown to be the result of four-wave mixing, leading to analytical expressions of the signal obtained which allow for improved optimization of systems that exploit these effects. |
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670 |
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Polyakov, Sergey V.; Migdalla, Alan L. |
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Quantum radiometry |
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2009 |
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J. Modern Opt. |
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56 |
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9 |
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1045-1052 |
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We review radiometric techniques that take advantage of photon counting and stem from the quantum laws of nature. We present a brief history of metrological experiments and review the current state of experimental quantum radiometry. |
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671 |
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Yates, S. J. C.; Baryshev, A. M.; Baselmans, J. J. A.; Klein, B.; Güsten, R. |
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Fast Fourier transform spectrometer readout for large arrays of microwave kinetic inductance detectors |
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2009 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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95 |
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4 |
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3 |
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Microwave kinetic inductance detectors have great potential for large, very sensitive detector arrays for use in, for example, submillimeter imaging. Being intrinsically readout in the frequency domain, they are particularly suited for frequency domain multiplexing allowing ~1000 s of devices to be readout with one pair of coaxial cables. However, this moves the complexity of the detector from the cryogenics to the warm electronics. We present here the concept and experimental demonstration of the use of fast Fourier transform spectrometer readout, showing no deterioration of the noise performance compared to the low noise analog mixing while allowing high multiplexing ratios. |
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Minaeva, Olga; Bonato, Cristian; Saleh, Bahaa E. A.; Simon, David S.; Sergienko, Alexander V. |
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Odd- and even-order dispersion cancellation in quantum interferometry |
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2009 |
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Phys. Rev. Lett. |
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Phys. Rev. Lett. |
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102 |
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10 |
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4 |
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We describe a novel effect involving odd-order dispersion cancellation. We demonstrate that odd- and even-order dispersion cancellation may be obtained in different regions of a single quantum interferogram using frequency-anticorrelated entangled photons and a new type of quantum interferometer. This offers new opportunities for quantum communication and metrology in dispersive media. |
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Ожегов, Р. В.; Окунев, О. В.; Гольцман, Г. Н.; Филиппенко, Л. В.; Кошелец, В. П. |
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Флуктуационная чувствительность сверхпроводящего интегрального приемника терагерцового диапазона частот |
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2009 |
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Радиотехника и электроника |
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Радиотех. электроник. |
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54 |
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6 |
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750-755 |
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Исследована зависимость флуктуационной чувствительности сверхпроводящего интегрального приемника (СИП) от шумовой температуры приемника и величины входного сигнала. Измерена рекордная флуктуационная чувствительность приемника (13 ± 2 мК), полученная при шумовой температуре приемника 200 К, ширине полосы промежуточных частот 4 ГГц и постоянной времени 1 с. При уменьшении входного сигнала наблюдалось улучшение флуктуационной чувствительности; предложено обÑŠяснение полученного эффекта: причиной является уменьшение влияния нестабильностей источников питания приемника и усилительного тракта при снижении входного сигнала. |
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