95 research outputs found
Formation of Non-reciprocal Bands in Magnetized Diatomic Plasmonic Chains
We show that non-reciprocal bands can be formed in a magnetized periodic
chain of spherical plasmonic particles with two particles per unit cell.
Simplified form of symmetry operators in dipole approximations are used to
demonstrate explicitly the relation between spectral non-reciprocity and broken
spatial-temporal symmetries. Due to hybridization among plasmon modes and free
photon modes, strong spectral non-reciprocity appears in region slightly below
the lightline, where highly directed guiding of energy can be supported. The
results may provide a clear guidance on the design of one-way waveguides
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
Super-resolution image transfer by a vortex-like metamaterial
We propose a vortex-like metamaterial device that is capable of transferring
image along a spiral route without losing subwavelength information of the
image. The super-resolution image can be guided and magnified at the same time
with one single design. Our design may provide insights in manipulating
super-resolution image in a more flexible manner. Examples are given and
illustrated with numerical simulations.Comment: 7 pages, 6 figure
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
Photon Emission Rate Engineering using Graphene Nanodisc Cavities
In this work, we present a systematic study of the plasmon modes in a system
of vertically stacked pair of graphene discs. Quasistatic approximation is used
to model the eigenmodes of the system. Eigen-response theory is employed to
explain the spatial dependence of the coupling between the plasmon modes and a
quantum emitter. These results show a good match between the semi-analytical
calculation and full-wave simulations. Secondly, we have shown that it is
possible to engineer the decay rates of a quantum emitter placed inside and
near this cavity, using Fermi level tuning, via gate voltages and variation of
emitter location and polarization. We highlighted that by coupling to the
bright plasmon mode, the radiative efficiency of the emitter can be enhanced
compared to the single graphene disc case, whereas the dark plasmon mode
suppresses the radiative efficiency
Tunable light-matter interaction and the role of hyperbolicity in graphene-hBN system
Hexagonal boron nitride (hBN) is a natural hyperbolic material which can also
accommodate highly dispersive surface phonon-polariton modes. In this paper, we
examine theoretically the mid-infrared optical properties of graphene-hBN
heterostructures derived from their coupled plasmon-phonon modes. We found that
the graphene plasmon couples differently with the phonons of the two
Reststrahlen bands, owing to their different hyperbolicity. This also leads to
distinctively different interaction between an external quantum emitter and the
plasmon-phonon modes in the two bands, leading to substantial modification of
its spectrum. The coupling to graphene plasmons allows for additional gate
tunability in the Purcell factor, and narrow dips in its emission spectra
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