The Experts below are selected from a list of 32124 Experts worldwide ranked by ideXlab platform
N. F. Van Hulst - One of the best experts on this subject based on the ideXlab platform.
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Optical Antennas direct single-molecule emission
Nature Photonics, 2008Co-Authors: T. H. Taminiau, Fernando D. Stefani, Franciscus B. Segerink, N. F. Van HulstAbstract:Antennas have been used for more than a century to control the emission and collection of Radio and microwave radiation(1). An optical analogue is of great interest as it will allow unique control of absorption and emission(2,3) at the nanometre scale(4). Despite the intense recent research on optical Antennas(5 - 8), one of the main functions of traditional Antennas, the directing of radiation, remains a challenge at optical frequencies. Here we experimentally demonstrate control of the emission direction of individual molecules by reversible coupling to an optical monopole antenna. We show how the angular emission of the coupled system is determined by the dominant antenna mode - that is, the antenna design - regardless of molecular orientation. This result reveals the role of the plasmon mode in the emission process and provides a clear guideline how to exploit the large available library of Radio Antennas to direct emission in nano-optical microscopy(9,10), spectroscopy(11,12) and light-emitting devices, including single-photon sources(13 - 15).
J Blumer - One of the best experts on this subject based on the ideXlab platform.
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amplitude calibration of a digital Radio antenna array for measuring cosmic ray air showers
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2008Co-Authors: S Nehls, J Blumer, A Hakenjos, M J Arts, H Bozdog, W A Van Cappellen, H Falcke, A Haungs, A HornefferAbstract:Radio pulses are emitted during the development of air showers, where air showers are generated by ultra-high energy cosmic rays entering the Earth’s atmosphere. These nano second short pulses are presently investigated by various experiments for the purpose of using them as a new detection technique for cosmic particles. For an array of 30 digital Radio Antennas (LOPES experiment) an absolute amplitude calibration of the Radio Antennas including the full electronic chain of the data acquisition system is performed, in order to estimate absolute values of the electric field strength for these short Radio pulses. This is mandatory, because the measured Radio signals in the MHz frequency range have to be compared with theoretical estimates and with predictions from Monte Carlo simulations to reconstruct features of the primary cosmic particle. A commercial reference Radio emitter is used to estimate frequency dependent correction factors for each single antenna of the Radio antenna array. The expected received power is related to the power recorded by the full electronic chain. Systematic uncertainties due to different environmental conditions and the described calibration procedure are of order 20 %.
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Radio emission of highly inclined cosmic ray air showers measured with lopes
Astronomy and Astrophysics, 2007Co-Authors: J Petrovic, W D Apel, T Asch, L Bahren, A Bercuci, P L Biermann, J BlumerAbstract:Aims. The capability of Radio antenna arrays to measure cosmic ray air showers with very large zenith angles is explored. This is important, since a possible neutrino detection has to fulfill two requirements. First: Antennas should be able to detect very inclined cosmic ray air showers, and second: it should be possible to estimate the distance to the shower maximum, since neutrinos are most likely to travel far through the Earth’s atmosphere without interaction and induce air showers close to the ground. Methods. LOPES (LOFAR PrototypE Station; LOFAR – LOw Frequency ARray), an array of dipole Antennas, is used for the detection of inclined cosmic ray air showers. LOPES is co-located and triggered by the KASCADE (KArlsruhe Shower Core and Array DEtector) experiment, which also provides information on air shower properties such as electron and muon numbers on the ground, as well as the arrival direction. Radio emission of nearly vertical cosmic ray air showers has been detected by LOPES. Results. LOPES-10 (the first phase of LOPES, consisting of 10 Antennas) detected a significant number of cosmic ray air showers with a zenith angle larger than 50 ◦ , and many of these have very high Radio field strengths. The most inclined event that has been detected with LOPES-10 has a zenith angle of almost 80 ◦ . This is proof that the new technique is also applicable for cosmic ray air showers with high inclinations, which in the case that they are initiated close to the ground, can be a signature of neutrino events. Conclusions. Our results indicate that arrays of simple Radio Antennas can be used for the detection of highly inclined air showers, which might be triggered by neutrinos. In addition, we found that the Radio pulse height (normalized with the muon number) for highly inclined events increases with the geomagnetic angle, which confirms the geomagnetic origin of Radio emission in cosmic ray air showers.
T. H. Taminiau - One of the best experts on this subject based on the ideXlab platform.
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Optical Antennas direct single-molecule emission
Nature Photonics, 2008Co-Authors: T. H. Taminiau, Fernando D. Stefani, Franciscus B. Segerink, N. F. Van HulstAbstract:Antennas have been used for more than a century to control the emission and collection of Radio and microwave radiation(1). An optical analogue is of great interest as it will allow unique control of absorption and emission(2,3) at the nanometre scale(4). Despite the intense recent research on optical Antennas(5 - 8), one of the main functions of traditional Antennas, the directing of radiation, remains a challenge at optical frequencies. Here we experimentally demonstrate control of the emission direction of individual molecules by reversible coupling to an optical monopole antenna. We show how the angular emission of the coupled system is determined by the dominant antenna mode - that is, the antenna design - regardless of molecular orientation. This result reveals the role of the plasmon mode in the emission process and provides a clear guideline how to exploit the large available library of Radio Antennas to direct emission in nano-optical microscopy(9,10), spectroscopy(11,12) and light-emitting devices, including single-photon sources(13 - 15).
A Zaslavsky - One of the best experts on this subject based on the ideXlab platform.
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interplanetary dust detection by Radio Antennas mass calibration and fluxes measured by stereo waves
Journal of Geophysical Research, 2012Co-Authors: A Zaslavsky, N Meyervernet, Ingrid Mann, A Czechowski, K Issautier, Le G Chat, F Pantellini, K GoetzAbstract:[1] We analyze dust impacts recorded by the S/WAVES Radio instrument onboard the two STEREO spacecraft near 1 A.U. during the period 2007–2010. The impact of a dust particle on a spacecraft produces a plasma cloud whose associated electric field can be detected by on-board electric Antennas. For this study we use the electric potential time series recorded by the waveform sampler of the instrument. The high time resolution and long sampling times of this measurement enable us to deduce considerably more information than in previous studies based on the dynamic power spectra provided by the same instrument or by Radio instruments onboard other spacecraft. The large detection area compared to conventional dust detectors provides flux data with a better statistics. We show that the dust-generated signals are of two kinds, corresponding to impacts of dust from distinctly different mass ranges. We propose calibration formulas for these signals and show that we are able to use S/WAVES as a dust detector with convincing results both in the nanometer and micrometer size ranges. In the latter, the orbital motion of the spacecraft enables us to distinguish between interstellar and interplanetary dust components. Our measurements cover the mass intervals ∼10−22–10−20 kg and ∼10−17 − 5 × 10−16 kg. The flux of the larger dust agrees with measurements of other instruments on different spacecraft.
Fernando D. Stefani - One of the best experts on this subject based on the ideXlab platform.
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Optical Antennas direct single-molecule emission
Nature Photonics, 2008Co-Authors: T. H. Taminiau, Fernando D. Stefani, Franciscus B. Segerink, N. F. Van HulstAbstract:Antennas have been used for more than a century to control the emission and collection of Radio and microwave radiation(1). An optical analogue is of great interest as it will allow unique control of absorption and emission(2,3) at the nanometre scale(4). Despite the intense recent research on optical Antennas(5 - 8), one of the main functions of traditional Antennas, the directing of radiation, remains a challenge at optical frequencies. Here we experimentally demonstrate control of the emission direction of individual molecules by reversible coupling to an optical monopole antenna. We show how the angular emission of the coupled system is determined by the dominant antenna mode - that is, the antenna design - regardless of molecular orientation. This result reveals the role of the plasmon mode in the emission process and provides a clear guideline how to exploit the large available library of Radio Antennas to direct emission in nano-optical microscopy(9,10), spectroscopy(11,12) and light-emitting devices, including single-photon sources(13 - 15).