4,944 research outputs found
Plasmonic atoms and plasmonic molecules
The proposed paradigm of plasmonic atoms and plasmonic molecules allows one
to describe and predict the strongly localized plasmonic oscillations in the
clusters of nanoparticles and some other nanostructures in uniform way.
Strongly localized plasmonic molecules near the contacting surfaces might
become the fundamental elements (by analogy with Lego bricks) for a
construction of fully integrated opto-electronic nanodevices of any complexity
and scale of integration.Comment: 30 pages, 16 figure
Mixing of spin and orbital angular momenta via second-harmonic generation in plasmonic and dielectric chiral nanostructures
We present a theoretical study of the characteristics of the nonlinear
spin-orbital angular momentum coupling induced by second-harmonic generation in
plasmonic and dielectric nanostructures made of centrosymmetric materials. In
particular, the connection between the phase singularities and polarization
helicities in the longitudinal components of the fundamental and
second-harmonic optical fields and the scatterer symmetry properties are
discussed. By in-depth comparison between the interaction of structured optical
beams with plasmonic and dielectric nanostructures, we have found that
all-dielectric and plasmonic nanostructures that exhibit magnetic and electric
resonances have comparable second-harmonic conversion efficiency. In addition,
mechanisms for second-harmonic enhancement for single and chiral clusters of
scatterers are unveiled and the relationships between the content of optical
angular momentum of the incident optical beams and the enhancement of nonlinear
light scattering is discussed. In particular, we formulate a general angular
momenta conservation law for the nonlinear spin-orbital angular momentum
interaction, which includes the quasi-angular-momentum of chiral structures
with different-order rotational symmetry. As a key conclusion of our study
relevant to nanophotonics, we argue that all-dielectric nanostructures provide
a more suitable platform to investigate experimentally the nonlinear
interaction between spin and orbital angular momenta, as compared to plasmonic
ones, chiefly due to their narrower resonance peaks, lower intrinsic losses,
and higher sustainable optical power
Coherent magnetic plasmon modes in a contacting gold nano-sphere chain on a gold Slab
A coupled magnetic resonator waveguide, composed of a contacting gold
nanosphere chain on a gold slab, is proposed and investigated. A broadband
coherent magnetic plasmon mode can be excited in this one dimensional
nanostructure. By employing the Lagrangian formalism and the Fourier transform
method, the dispersion properties of the wave vector and group velocity of the
magnetic plasmon mode are investigated. Small group velocity can be obtained
from this system which can be applied as subwavelength slow wave waveguides.Comment: 11pages, 5 figures, This work is published at Optics Express 19,
23782 (2011
Substrate influence on the plasmonic response of clusters of spherical nanoparticles
The plasmonic response of nanoparticles is exploited in many subfields of
science and engineering to enhance optical signals associated with probes of
nanoscale and subnanoscale entities. We develop a numerical algorithm based on
previous theoretical work that addresses the influence of a substrate on the
plasmonic response of collections of nanoparticles of spherical shape. Our
method is a real space approach within the quasi-static limit that can be
applied to a wide range of structures. We illustrate the role of the substrate
through numerical calculations that explore single nanospheres and nanosphere
dimers fabricated from either a Drude model metal or from silver on dielectric
substrates, and from dielectric spheres on silver substrates.Comment: 12 pages, 13 figure
How nonlocal damping reduces plasmon-enhanced fluorescence in ultranarrow gaps
The nonclassical modification of plasmon-assisted fluorescence enhancement is
theoretically explored by placing two-level dipole emitters at the narrow gaps
encountered in canonical plasmonic architectures, namely dimers and trimers of
different metallic nanoparticles. Through detailed simulations, in comparison
with appropriate analytical modelling, it is shown that within classical
electrodynamics, and for the reduced separations explored here, fluorescence
enhancement factors of the order of can be achieved, with a divergent
behaviour as the particle touching regime is approached. This remarkable
prediction is mainly governed by the dramatic increase in excitation rate
triggered by the corresponding field enhancement inside the gaps. Nevertheless,
once nonclassical corrections are included, the amplification factors decrease
by up to two orders of magnitude and a saturation regime for narrower gaps is
reached. These nonclassical limitations are demonstrated by simulations based
on the generalised nonlocal optical response theory, which accounts in an
efficient way not only for nonlocal screening, but also for the enhanced Landau
damping near the metal surface. A simple strategy to introduce nonlocal
corrections to the analytic solutions is also proposed. It is therefore shown
that the nonlocal optical response of the metal imposes more realistic, finite
upper bounds to the enhancement feasible with ultrasmall plasmonic cavities,
thus providing a theoretical description closer to state of the art
experiments
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