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| Author |
Risacher, C.; Meledin, D.; Belitsky, V.; Bergman, P. |
| Title |
First 1.3 THz observations at the APEX telescope |
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Conference Article |
| Year |
2009 |
Publication |
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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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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Journal Article |
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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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Ozhegov, R. V.; Okunev, O. V.; Gol’tsman, G. N.; Filippenko, L. V.; Koshelets, V. P. |
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Noise equivalent temperature difference of a superconducting integrated terahertz receiver |
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Journal Article |
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2009 |
Publication |
J. Commun. Technol. Electron. |
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J. Commun. Technol. Electron. |
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54 |
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6 |
Pages |
716-720 |
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SIS mixer SIR NETD, FFO, harmonic mixer |
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The dependence of the noise equivalent temperature difference (NETD) of a superconducting integrated receiver (SIR) on the receiver noise temperature and the inputsignal level has been investigated. An unprecedented NETD of 13±2 mK has been measured at a SIR noise temperature of 200 K, intermediate-frequency bandwidth of 4 GHz, and time constant of 1 s. With a decrease in the input signal, an improvement in the NETD is observed. This effect is explained by a reduction in the influence of the instabilities of the receiver power supply and the amplification circuit that occur when the input signal is decreased. |
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1064-2269 |
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1400 |
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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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Journal Article |
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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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Hadfield, Robert H. |
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Single-photon detectors for optical quantum information applications |
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Journal Article |
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2009 |
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Nature Photonics |
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Nature Photonics |
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3 |
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696-705 |
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SPD |
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The past decade has seen a dramatic increase in interest in new single-photon detector technologies. A major cause of this trend has undoubtedly been the push towards optical quantum information applications such as quantum key distribution. These new applications place extreme demands on detector performance that go beyond the capabilities of established single-photon detectors. There has been considerable effort to improve conventional photon-counting detectors and to transform new device concepts into workable technologies for optical quantum information applications. This Review aims to highlight the significant recent progress made in improving single-photon detector technologies, and the impact that these developments will have on quantum optics and quantum information science. |
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