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Author Bryant, Garnett W.; García de Abajo, F. Javier; Aizpurua, Javier
Title Mapping the Plasmon Resonances of Metallic Nanoantennas Type Journal Article
Year 2008 Publication Nano Letters Abbreviated Journal (up) Nano Lett.
Volume 5 Issue 2 Pages 631-636
Keywords optical antennas
Abstract We study the light scattering and surface plasmon resonances of Au nanorods that are commonly used as optical nanoantennas in analogy to dipole radio antennas for chemical and biodetection field-enhanced spectroscopies and scanned-probe microscopies. With the use of the boundary element method, we calculate the nanorod near-field and far-field response to show how the nanorod shape and dimensions determine its optical response. A full mapping of the size (length and radius) dependence for Au nanorods is obtained. The dipolar plasmon resonance wavelength λ shows a nearly linear dependence on total rod length L out to the largest lengths that we study. However, L is always substantially less than λ/2, indicating the difference between optical nanoantennas and long-wavelength traditional λ/2 antennas. Although it is often assumed that the plasmon wavelength scales with the nanorod aspect ratio, we find that this scaling does not apply except in the extreme limit of very small, spherical nanoparticles. The plasmon response depends critically on both the rod length and radius. Large (500 nm) differences in resonance wavelength are found for structures with different sizes but with the same aspect ratio. In addition, the plasmon resonance deduced from the near-field enhancement can be significantly red-shifted due to retardation from the resonance in far-field scattering. Large differences in near-field and far-field response, together with the breakdown of the simple scaling law must be accounted for in the choice and design of metallic λ/2 nanoantennas. We provide a general, practical map of the resonances for use in locating the desired response for gold nanoantennas.
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Call Number RPLAB @ gujma @ Serial 737
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Author Divochiy, Aleksander; Marsili, Francesco; Bitauld, David; Gaggero, Alessandro; Leoni, Roberto; Mattioli, Francesco; Korneev, Alexander; Seleznev, Vitaliy; Kaurova, Nataliya; Minaeva, Olga; Gol'tsman, Gregory; Lagoudakis, Konstantinos G.; Benkhaoul, Moushab; Lévy, Francis; Fiore, Andrea
Title Superconducting nanowire photon-number-resolving detector at telecommunication wavelengths Type Journal Article
Year 2008 Publication Nat. Photon. Abbreviated Journal (up) Nat. Photon.
Volume 2 Issue 5 Pages 302-306
Keywords SSPD, photon-number-resolving
Abstract Optical-to-electrical conversion, which is the basis of the operation of optical detectors, can be linear or nonlinear. When high sensitivities are needed, single-photon detectors are used, which operate in a strongly nonlinear mode, their response being independent of the number of detected photons. However, photon-number-resolving detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication and quantum information processing, the photon-number-resolving functionality is key to many protocols, such as the implementation of quantum repeaters1 and linear-optics quantum computing2. A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, such as in long-distance optical communications, fluorescence spectroscopy and optical time-domain reflectometry. We demonstrate here a photon-number-resolving detector based on parallel superconducting nanowires and capable of counting up to four photons at telecommunication wavelengths, with an ultralow dark count rate and high counting frequency.
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Call Number Serial 916
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Author Pirandola, Stefano; Mancini, Stefano; Lloyd, Seth; Braunstein, Samuel L.
Title Continuous-variable quantum cryptography using two-way quantum communication Type Journal Article
Year 2008 Publication Nature Physics Abbreviated Journal (up) Nat. Phys.
Volume 4 Issue 9 Pages 726-730
Keywords fromIPMRAS
Abstract Quantum cryptography has recently been extended to continuous-variable systems, such as the bosonic modes of the electromagnetic field possessing continuous degrees of freedom. In particular, several cryptographic protocols have been proposed and experimentally implemented using bosonic modes with Gaussian statistics. These protocols have shown the possibility of reaching very high secret key rates, even in the presence of strong losses in the quantum communication channel. Despite this robustness to loss, their security can be affected by more general attacks where extra Gaussian noise is introduced by the eavesdropper. Here, we show a `hardware solution' for enhancing the security thresholds of these protocols. This is possible by extending them to two-way quantum communication where subsequent uses of the quantum channel are suitably combined. In the resulting two-way schemes, one of the honest parties assists the secret encoding of the other, with the chance of a non-trivial superadditive enhancement of the security thresholds. These results should enable the extension of quantum cryptography to more complex quantum communications.
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Call Number RPLAB @ gujma @ Serial 798
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Author Li, Mo; Pernice, W. H. P.; Xiong, C.; Baehr-Jones, T.; Hochberg, M.; Tang, H. X.
Title Harnessing optical forces in integrated photonic circuits Type Journal Article
Year 2008 Publication Nature Abbreviated Journal (up) Nature
Volume 456 Issue 7221 Pages 480-484
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ISSN 0028-0836 ISBN Medium
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Call Number RPLAB @ s @ Serial 425
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Author Wei, Jian; Olaya, David; Karasik, Boris S.; Pereverzev, Sergey V.; Sergeev, Andrei V.; Gershenson, Michael E.
Title Ultrasensitive hot-electron nanobolometers for terahertz astrophysics Type Journal Article
Year 2008 Publication Nature Nanotechnology Abbreviated Journal (up) Nature Nanotech
Volume 3 Issue 8 Pages 496-500
Keywords HEB, Ti/NbN, single terahertz photons, detection
Abstract The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers – devices for measuring the energy of electromagnetic radiation—with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment;

second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron–phonon interactions, becomes very small at low temperatures (10-16 WK-1 at 40 mK). These devices, with a heat capacity of 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting.
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ISSN 1748-3387 ISBN Medium
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Call Number Serial 576
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