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D. Henrich, L. Rehm S. Dörner, M. Hofherr, K. Il'in, A. Semenov, and M. Siegel |
| Title |
Detection efficiency of a spiral-nanowire superconducting single-photon detector |
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Journal Article |
| Year |
2012 |
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Critical current, Nanoscale devices, Superconducting photodetectors. |
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We investigate the detection efficiency of a spiral layout of a Superconducting Nanowire Single-Photon Detector (SNSPD). The design is less susceptible to the critical current reduction in sharp turns of the nanowire than the conventional meander design. Detector samples with different nanowire width from 300 to 100 nm are patterned from a 4 nm thick NbN film deposited on sapphire substrates. The critical current IC at 4.2 K for spiral, meander, and simple bridge structures is measured and compared. On the 100 nm wide samples, the detection efficiency is measured in the wavelength range 400-1700 nm and the cut-off wavelength of the hot-spot plateau is determined. In the optical range, the spiral detector reaches a detection efficiency of 27.6%, which is ~1.5 times the value of the meander. In the infrared range the detection efficiency is more than doubled. |
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D. Henrich, L. Rehm S. Dörner, M. Hofherr, K. Il'in, A. Semenov, and M. Siegel |
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RPLAB @ seleznev @ |
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880 |
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De Luca, M.; Gupta, H.; Neufeld, D.; Gerin, M.; Teyssier, D.; Drouin, B. J.; Pearson, J. C.; Lis, D. C.; Monje, R.; Phillips, T. G.; Goicoechea, J. R.; Godard, B.; Falgarone, E.; Coutens, A.; Bell, T. A. |
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Herschel/HIFI discovery of HCL+ in the interstellar medium |
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Journal Article |
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2012 |
Publication |
Astrophys. J. Lett. |
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751 |
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2 |
Pages |
L37 |
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HEB mixer applications, HIFI, Herschel |
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The radical ion HCl+, a key intermediate in the chlorine chemistry of the interstellar gas, has been identified for the first time in the interstellar medium with the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared. The ground-state rotational transition of H35Cl+, 2Π3/2 J = 5/2-3/2, showing Λ-doubling and hyperfine structure, is detected in absorption toward the Galactic star-forming regions W31C (G10.6-0.4) and W49N. The complex interstellar absorption features are modeled by convolving in velocity space the opacity profiles of other molecular tracers toward the same sources with the fine and hyperfine structure of HCl+. This structure is derived from a combined analysis of optical data from the literature and new laboratory measurements of pure rotational transitions, reported in the accompanying Letter by Gupta et al. The models reproduce well the interstellar absorption, and the frequencies inferred from the astronomical observations are in exact agreement with those calculated using spectroscopic constants derived from the laboratory data. The detection of H37Cl+ toward W31C, with a column density consistent with the expected 35Cl/37Cl isotopic ratio, provides additional evidence for the identification. A comparison with the chemically related molecules HCl and H2Cl+ yields an abundance ratio of unity with both species (HCl+ : H2Cl+ : HCl ~ 1). These observations also yield the unexpected result that HCl+ accounts for 3%-5% of the gas-phase chlorine toward W49N and W31C, values several times larger than the maximum fraction (~1%) predicted by chemical models. |
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1092 |
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Gao, Jie; McMillan, James F.; Wong, Chee Wei |
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Nanophotonics: Remote on-chip coupling |
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Journal Article |
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2012 |
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Nature Photonics |
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Nat. Photon. |
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6 |
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1 |
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7-8 |
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fromIPMRAS |
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Scientists have demonstrated strongly coupled photon states between two distant high-Q photonic crystal cavities connected by a photonic crystal waveguide. Remote dynamic control over the coupled states could aid the development of delay lines, optical buffers and qubit operations in both classical and quantum information processing. |
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RPLAB @ gujma @ |
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779 |
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Ghali, Mohsen; Ohtani1, Keita; Ohno, Yuzo; Ohno, Hideo |
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Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field |
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Journal Article |
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2012 |
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Nature Communications |
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Nat. Comm. |
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3 |
Issue |
661 |
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6 |
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fromIPMRAS |
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Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton-exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72 ± 0.05. |
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RPLAB @ gujma @ |
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769 |
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Goulielmakis, Eleftherios |
| Title |
Attosecond photonics: Extreme ultraviolet catastrophes |
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Journal Article |
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2012 |
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Nature Photonics |
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Nat. Photon. |
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6 |
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3 |
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142-143 |
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fromIPMRAS |
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Extreme ultraviolet attosecond pulses, which emerge from the interaction of atoms with intense laser fields, play a central role in modern ultrafast science and the exploration of electron behaviour. Recent work now shows that catastrophe theory can help optimize the properties of these pulses. |
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RPLAB @ gujma @ |
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791 |
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