179 research outputs found
Transmission of plasmons through a nanowire
Exact quantitative understanding of plasmon propagation along nanowires is
mandatory for designing and creating functional devices. Here we investigate
plasmon transmission through top-down fabricated monocrystalline gold nanowires
on a glass substrate. We show that the transmission through finite-length
nanowires can be described by Fabry-P\'{e}rot oscillations that beat with
free-space propagating light launched at the incoupling end. Using an extended
Fabry-P\'{e}rot model, experimental and simulated length dependent transmission
signals agree quantitatively with a fully analytical model.Comment: 5 pages, 4 figure
Electromechanically Tunable Suspended Optical Nano-antenna
Coupling mechanical degrees of freedom with plasmonic resonances has
potential applications in optomechanics, sensing, and active plasmonics. Here
we demonstrate a suspended two-wire plasmonic nano-antenna acting like a
nano-electrometer. The antenna wires are supported and electrically connected
via thin leads without disturbing the antenna resonance. As a voltage is
applied, equal charges are induced on both antenna wires. The resulting
equilibrium between the repulsive Coulomb force and the restoring elastic
bending force enables us to precisely control the gap size. As a result the
resonance wavelength and the field enhancement of the suspended optical
nano-antenna (SONA) can be reversibly tuned. Our experiments highlight the
potential to realize large bandwidth optical nanoelectromechanical systems
(NEMS)
Driving plasmonic nanoantennas at perfect impedance matching using generalized coherent perfect absorption
Coherent perfect absorption (CPA) describes the absence of all outgoing modes
from a lossy resonator, driven by lossless incoming modes. Here, we show that
for nanoresonators that also exhibit radiative losses, e.g. plasmonic
nanoantennas, a generalized version of CPA (gCPA) can be applied. In gCPA
outgoing modes are suppressed only for a subset of (guided plasmonic) modes
while other (radiative) modes are treated as additional loss channels - a
situation typically referred to as perfect impedance matching. Here we make use
of gCPA to show how to achieve perfect impedance matching between a single
nanowire plasmonic waveguide and a plasmonic nanoantenna. Antennas with both
radiant and subradiant characteristics are considered. We further demonstrate
potential applications in back-ground-free sensing
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Driving plasmonic nanoantennas at perfect impedance matching using generalized coherent perfect absorption
Coherent perfect absorption (CPA) describes the absence of all outgoing modes from a lossy resonator, driven by lossless incoming modes. Here, we show that for nanoresonators that also exhibit radiative losses, e.g., plasmonic nanoantennas, a generalized version of CPA (gCPA) can be applied. In gCPA outgoing modes are suppressed only for a subset of (guided plasmonic) modes while other (radiative) modes are treated as additional loss channels - a situation typically referred to as perfect impedance matching. Here we make use of gCPA to show how to achieve perfect impedance matching between a single nanowire plasmonic waveguide and a plasmonic nanoantenna. Antennas with both radiant and subradiant characteristics are considered. We further demonstrate potential applications in background-free sensing
Recordkeeping Alters Economic History by Promoting Reciprocity
We experimentally demonstrate a causal link between recordkeeping and reciprocal exchange. Recordkeeping improves memory of past interactions in a complex exchange environment, which promotes reputation formation and decision coordination. Economies with recordkeeping exhibit a beneficially altered economic history where the risks of exchanging with strangers are substantially lessened. Our findings are consistent with prior assertions that complex and extensive reciprocity requires sophisticated memory to store information on past transactions. We offer insights on this research by scientifically demonstrating that reciprocity can be facilitated by information storage external to the brain. This is consistent with the archaeological record, which suggests that prehistoric transaction records and the invention of writing for recordkeeping were linked to increased complexity in human interaction
Observations of Gravity Wave Breakdown into Ripples Associated with Dynamical Instabilities
The breakdown of a high-frequency quasi-monochromatic gravity wave into smallscale ripples in OH airglow was observed on the night of 28 October 2003 at Maui, Hawaii (20.7ºN, 156.3ºW). The ripples lasted ~20 min. The phase fronts of the ripples were parallel to the phase fronts of the breaking wave. The mechanism for the ripple generation is investigated using simultaneous wind and temperature measurements made by a sodium (Na) lidar. The observations suggest that the wave breaking and the subsequent appearance of ripples were related to dynamical (or Kelvin-Helmholtz) instabilities. The characteristics of the ripples, including the alignment of the phase fronts with respect to the wind shear, the motion of the ripples, and the horizontal separation of the ripple fronts were consistent with their attribution to Kelvin-Helmholtz billows. It is likely that the dynamical instability was initiated by the superposition of the background wind shear and the shear induced by the wave. The wind shear, the mean wind acceleration, and the propagation of the breaking wave were found to be in the same direction, suggesting that wave-mean flow interactions contributed significantly to the generation of the strong (\u3e40 m/s/km) wind shear and instability
Spectral-interference microscopy for characterization of functional plasmonic elements
Plasmonic modes supported by noble-metal nanostructures offer strong subwavelength electric-field confinement and promise the realization of nanometer-scale integrated optical circuits with well-defined functionality. In order to measure the spectral and spatial response functions of such plasmonic elements, we combine a confocal microscope setup with spectral interferometry detection. The setup, data acquisition, and data evaluation are discussed in detail by means of exemplary experiments involving propagating plasmons transmitted through silver nanowires. By considering and experimentally calibrating any setup-inherent signal delay with an accuracy of 1 fs, we are able to extract correct timing information of propagating plasmons. The method can be applied, e.g., to determine the dispersion and group velocity of propagating plasmons in nanostructures, and can be extended towards the investigation of nonlinear phenomena
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