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Author |
Novotny, Lukas |
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Title |
Effective wavelength scaling for optical antennas |
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Journal Article |
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2007 |
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Phys. Rev. Lett. |
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Phys. Rev. Lett. |
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98 |
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26 |
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266802(1-4) |
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optical antennas |
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In antenna theory, antenna parameters are directly related to the wavelength λ of incident radiation, but this scaling fails at optical frequencies where metals behave as strongly coupled plasmas. In this Letter we show that antenna designs can be transferred to the optical frequency regime by replacing λ by a linearly scaled effective wavelength λeff=n1+n2λ/λp, with λp being the plasma wavelength and n1, n2 being coefficients that depend on geometry and material properties. It is assumed that the antenna is made of linear segments with radii Râ‰<aa>λ. Optical antennas hold great promise for increasing the efficiency of photovoltaics, light-emitting devices, and optical sensors. |
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RPLAB @ gujma @ |
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749 |
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Author |
Williams, Benjamin S. |
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Title |
Terahertz quantum-cascade lasers |
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Journal Article |
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2007 |
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Nature Photonics |
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1 |
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517-525 |
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QCL review |
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Six years after their birth, terahertz quantum-cascade lasers can now deliver milliwatts or more of continuous-wave coherent radiation throughout the terahertz range — the spectral regime between millimetre and infrared wavelengths, which has long resisted development. This paper reviews the state-of-the-art and future prospects for these lasers, including efforts to increase their operating temperatures, deliver higher output powers and emit longer wavelengths. |
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Морозов, Дмитрий Владимирович |
![find record details (via OpenURL) openurl](img/xref.gif)
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Title |
Приемные устройства терагерцового диапазона на эффекте разогрева двумерного электронного газа в гетероструктурах AlGaAs/GaAs |
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2007 |
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М. МПГУ |
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Ph.D. thesis |
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RPLAB @ s @ |
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Yang, J. K. W.; Kerman, A. J.; Dauler, E. A.; Anant, V.; Rosfjord, K. M.; Berggren, K. K. |
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Modeling the electrical and thermal response of superconducting nanowire single-photon detectors |
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Journal Article |
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2007 |
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IEEE Trans. Appl. Supercond. |
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17 |
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2 |
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581 - 585 |
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SSPD, modeling |
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We modeled the response of superconducting nanowire single-photon detectors during a photodetection event, taking into consideration only the thermal and electrical properties of a superconducting NbN nanowire on a sapphire substrate. Our calculations suggest that heating which occurs after the formation of a photo-induced resistive barrier is responsible for the generation of a measurable voltage pulse. We compared this numerical result with experimental data of a voltage pulse from a slow device, i.e. large kinetic inductance, and obtained a good fit. Using this electro-thermal model, we estimated the temperature rise and the resistance buildup in the nanowire, and the return current at which the nanowire becomes superconducting again. We also show that the reset time of these photodetectors can be decreased by the addition of a series resistance and provide supporting experimental data. Finally we present preliminary results on a detector latching behavior that can also be explained using the electro-thermal model. |
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Takesue, Hiroki; Nam, Sae Woo; Zhang, Qiang; Hadfield, Robert H.; Honjo, Toshimori; Tamaki, Kiyoshi; Yamamoto, Yoshihisa |
![find record details (via OpenURL) openurl](img/xref.gif)
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Title |
Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors |
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Journal Article |
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Year |
2007 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
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1 |
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343-348 |
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quantum cryptography, SSPD, QKD, DSP |
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no |
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RPLAB @ akorneev @ |
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609 |
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Author |
Koch, Martin |
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Title |
Terahertz communications: a 2020 vision |
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Book Chapter |
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Year |
2007 |
Publication |
NATO Security through Science Series |
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2007 |
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325-338 |
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Keywords |
terahertz THz communications |
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We discuss basic considerations for potential short-range THz communication systems which may replace or supplement present WLAN systems in 10–15 years from now. On the basis of a few fundamental estimations we show that such a system will need a line-of-sight connection between receiver and emitter. To circumvent the blocking of the direct line-of-sight connection indoor THz communication systems will also have to rely on non-line-of-sight paths which involve reflections off the walls. The reflectivity of the walls can be enhanced by dielectric mirrors. This new scheme makes steerable high-gain antennas a necessity. Hence, a wireless THz communication system can not be a simple extension of the existing technology of today's local area networks. Instead it involves completely new concepts and ideas that have not yet been worked upon. |
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594 |
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Author |
Khosropanah, P.; Gao, J. R.; Laauwen, W. M.; Hajenius, M; Klapwijk, T. M. |
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Title |
Low noise NbN hot electron bolometer mixer at 4.3 THz |
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Journal Article |
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Year |
2007 |
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Appl. Phys. Lett. |
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Appl. Phys. Lett. |
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91 |
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221111 (1 to 3) |
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NbN HEB mixers, NbN, contacts cleaning |
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We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3 THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300 K at the optimum local oscillator (LO) power of 330 nW, which is about 12 times the quantum noise (hnu/2kB). Our result indicates that there is no sign of degradation of the mixing process at the superterahertz frequencies. Moreover, a measurement method is introduced which allows us for an accurate determination of the sensitivity despite LO power fluctuations. |
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584 |
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Author |
Cao, Aiqin; Jiang, L.; Chen, S.H.; Antipov, S.V.; Shi, S.C. |
![find record details (via OpenURL) openurl](img/xref.gif)
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Title |
IF gain bandwidth of a quasi-optical NbN superconducting HEB mixer |
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Conference Article |
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Year |
2007 |
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Proc. International conference on microwave and millimeter wave technology |
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Proc. ICMMT |
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1-3 |
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HEB, mixer, gain bandwidth |
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In this paper, the intermediate frequency (IF) gain bandwidth of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer is investigated at 500 GHz with an IF system incorporating with a frequency down-converting scheme which is able to sweep the IF signal in a frequency range of 0.3-4 GHz. The IF gain bandwidth of the device is measured to be 1.5 GHz when it is biased at a voltage of the minimum noise temperature, and becomes larger when the bias voltage increases. |
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Builin |
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RPLAB @ lobanovyury @ |
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575 |
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Kampfrath, Tobias; Perfetti, Luca; von Volkmann, Konrad; Aguirre, Carla M.; Desjardins, Patrick; Martel, Richard; Frischkorn, Christian; Wolf, Martin |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Optical response of single-wall carbon nanotube sheets in the far-infrared spectral range from 1 THz to 40 THz |
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Journal Article |
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2007 |
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Physica Status Solidi (B) |
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Phys. Stat. Sol. (B) |
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244 |
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11 |
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3950-3954 |
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single wall, carbon nanotube, SWNT, SWCNT, CNT, detector, sensor, TDS |
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The optical properties of single-wall carbon nanotube sheets in the far-infrared have been investigated with THz time-domain spectroscopy. Over a wide frequency range from 1 THz to 40 THz, the complex dielectric function of the nanotube sample has been derived. Our data can be excellently reproduced by a Drude-Lorentz model function. The extracted fit parameters such as Lorentz resonance frequency and plasma frequency are consistent with values obtained by scanning tunneling techniques. We discuss the origin of both the Lorentz and Drude contribution in terms of direct and indirect optical transitions. |
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0370-1972 |
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Lieberzeit, P.; Afzal, A.; Rehman, A.; Dickert, F. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Nanoparticles for detecting pollutants and degradation processes with mass-sensitive sensors |
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Journal Article |
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2007 |
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Sensors and Actuators B: Chemical |
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Sensors and Actuators B: Chemical |
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127 |
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1 |
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132-136 |
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molecular imprinted polymer, MIP, recognition, quartz crystal microbalance, QCM, mass-sensitive sensor, detector |
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Compared with thin films, nanoparticle layers as coatings for QCM offer substantially increased interaction areas and sensitivities with favourable response times. Molybdenum disulphide (MoS2), e.g. has turned out to be a highly suitable material for interacting with thiols. The resulting materials are sufficiently soft according to Pearson to bind sulphur containing compounds reversibly. Depositing MoS2 nanoparticle submonolayers (particle size 200–300 nm) leads to an increase in sensor response by a factor of ten compared to a pure gold layer. Additionally, the nanoparticle layers show fully reversible sensor signals. Particle synthesis can also be combined with the molecular imprinting approach: by a precipitation technique, it is possible to generate molecularly imprinted TiO2 particles for engine oil degradation measurements. Compared with deposited thin layers, particles incorporate oxidised compounds from lubricants by a factor of two better. |
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0925-4005 |
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