2,276 research outputs found
Plasmonic angular momentum on metal-dielectric nano-wedges in a sectorial indefinite metamaterial
We present an analytical study to the structure-modulated plasmonic angular
momentum trapped on periodic metal-dielectric nano-wedges in the core region of
a sectorial indefinite metamaterial. Employing a transfer-matrix calculation
and a conformal-mapping technique, our theory is capable of dealing with
realistic configurations of arbitrary sector numbers and rounded wedge tips. We
demonstrate that in the deep-subwavelength regime strong electric field
carrying high azimuthal variation can exist within only ten-nanometer length
scale close to the structural center, and is naturally bounded by a
characteristic radius of the order of hundred-nanometer away from the center.
These extreme confining properties suggest that the structure under
investigation may be superior to the conventional metal-dielectric waveguides
or cavities in terms of nanoscale photonic manipulation.Comment: 16 pages, 9 figure
Cognitive Ability and Retiree Health Care Expenditure
Prior research indicates that retirees with less cognitive ability are at greater financial risk because they have lower incomes yet higher medical expenditures. Linking HRS data to administrative records, we evaluate two hypotheses about why this group spends more on health: (1) they are in worse health; (2) they receive more expensive or less effective care for the same conditions. We find that the bulk, but not all, of the cross-sectional relationship can be attributed to the poorer health of those with lower cognitive functioning. Much of this relationship appears to be driven by coincident declines in cognitive ability and health. While, in this respect, the data have important limitations, we find no evidence of substantial differences in care, conditional on observable health.
Theory of optical imaging beyond the diffraction limit with a far-field superlens
Recent theoretical and experimental studies have shown that imaging with
resolution well beyond the diffraction limit can be obtained with so-called
superlenses. Images formed by such superlenses are, however, in the near field
only, or a fraction of wavelength away from the lens. In this paper, we propose
a far-field superlens (FSL) device which is composed of a planar superlens with
periodical corrugation. We show in theory that when an object is placed in
close proximity of such a FSL, a unique image can be formed in far-field. As an
example, we demonstrate numerically that images of 40 nm lines with a 30 nm gap
can be obtained from far-field data with properly designed FSL working at 376nm
wavelength.Comment: 6 pages, 3 figure
Nonlocal description of sound propagation through an array of Helmholtz resonators
A generalized macroscopic nonlocal theory of sound propagation in
rigid-framed porous media saturated with a viscothermal fluid has been recently
proposed, which takes into account both temporal and spatial dispersion. Here,
we consider applying this theory capable to describe resonance effects, to the
case of sound propagation through an array of Helmholtz resonators whose
unusual metamaterial properties such as negative bulk moduli, have been
experimentally demonstrated. Three different calculations are performed,
validating the results of the nonlocal theory, relating to the
frequency-dependent Bloch wavenumber and bulk modulus of the first normal mode,
for 1D propagation in 2D or 3D periodic structures.Comment: 19 page
Optical Torque from Enhanced Scattering by Multipolar Plasmonic Resonance
We present a theoretical study of the optical angular momentum transfer from
a circularly polarized plane wave to thin metal nanoparticles of different
rotational symmetries. While absorption has been regarded as the predominant
mechanism of torque generation on the nanoscale, we demonstrate numerically how
the contribution from scattering can be enhanced by using multipolar plasmon
resonance. The multipolar modes in non-circular particles can convert the
angular momentum carried by the scattered field, thereby producing
scattering-dominant optical torque, while a circularly symmetric particle
cannot. Our results show that the optical torque induced by resonant scattering
can contribute to 80% of the total optical torque in gold particles. This
scattering-dominant torque generation is extremely mode-specific, and deserves
to be distinguished from the absorption-dominant mechanism. Our findings might
have applications in optical manipulation on the nanoscale as well as new
designs in plasmonics and metamaterials.Comment: main article 20 pages, 4 figures; supplementary material 6 pages, 2
figure
Transformation Optics scheme for two-dimensional materials
Two dimensional optical materials, such as graphene can be characterized by a
surface conductivity. So far, the transformation optics schemes have focused on
three dimensional properties such as permittivity and permeability
. In this paper, we use a scheme for transforming surface currents to
highlight that the surface conductivity transforms in a way different from
and . We use this surface conductivity transformation to
demonstrate an example problem of reducing scattering of plasmon mode from
sharp protrusions in graphene
Electron-photon scattering mediated by localized plasmons: A quantitative analysis by eigen-response theory
We show that the scattering interaction between a high energy electron and a
photon can be strongly enhanced by different types of localized plasmons in a
non-trivial way. The scattering interaction is predicted by an eigen-response
theory, numerically verified by finite-difference-time-domain simulation, and
experimentally verified by cathodoluminescence spectroscopy. We find that the
scattering interaction associated with dark plasmons can be as strong as that
of bright plasmons. Such a strong interaction may offer new opportunities to
improve single-plasmon detection and high-resolution characterization
techniques for high quality plasmonic materials.Comment: 4 pages, 4 figures (excluding Supporting Information
Topological magnetoplasmon
Classical wave fields are real-valued, ensuring the wave states at opposite
frequencies and momenta to be inherently identical. Such a particle-hole
symmetry can open up new possibilities for topological phenomena in classical
systems. Here we show that the historically studied two-dimensional (2D)
magnetoplasmon, which bears gapped bulk states and gapless one-way edge states
near zero frequency, is topologically analogous to the 2D topological p+\Ii p
superconductor with chiral Majorana edge states and zero modes. We further
predict a new type of one-way edge magnetoplasmon at the interface of opposite
magnetic domains, and demonstrate the existence of zero-frequency modes bounded
at the peripheries of a hollow disk. These findings can be readily verified in
experiment, and can greatly enrich the topological phases in bosonic and
classical systems.Comment: 12 pages, 6 figures, 1 supporting materia
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