16,109 research outputs found
Field enhancement in subnanometer metallic gaps
Motivated by recent experiments [Ward et al., Nature Nanotech. 5, 732
(2010)], we present here a theoretical analysis of the optical response of
sharp gold electrodes separated by a subnanometer gap. In particular, we have
used classical finite difference time domain simulations to investigate the
electric field distribution in these nanojunctions upon illumination. Our
results show a strong confinement of the field within the gap region, resulting
in a large enhancement compared to the incident field. Enhancement factors
exceeding 1000 are found for interelectrode distances on the order of a few
angstroms, which are fully compatible with the experimental findings. Such huge
enhancements originate from the coupling of the incident light to the
evanescent field of hybrid plasmons involving charge density oscillations in
both electrodes.Comment: 4 pages, 3 figures, to appear in Physical Review
Electric field enhancement with plasmonic colloidal nanoantennas excited by a silicon nitride waveguide
We investigate the feasibility of CMOS-compatible optical structures to
develop novel integrated spectroscopy systems. We show that local field
enhancement is achievable utilizing dimers of plasmonic nanospheres that can be
assembled from colloidal solutions on top of a CMOS-compatible optical
waveguide. The resonant dimer nanoantennas are excited by modes guided in the
integrated silicon nitride waveguide. Simulations show that 100 fold electric
field enhancement builds up in the dimer gap as compared to the waveguide
evanescent field amplitude at the same location. We investigate how the field
enhancement depends on dimer location, orientation, distance and excited
waveguide modes
Electromagnetic Field Enhancement in Bloch Surface Waves
We present a systematic comparison between guided modes supported by slab
waveguides and Bloch Surface Waves (BSWs) propagating at the surface of
truncated periodic multilayers. We show that, contrary to common belief, the
best surface field enhancement achievable for guided modes in a slab waveguide
is comparable to that observed for BSWs. At the same time, we demonstrate that,
if one is interested in maximizing the electromagnetic energy density at a
generic point of a dielectric planar structure, BSWs are often preferable to
modes in which light is confined uniquely by total internal reflection. Since
these results are wavelength independent and have been obtained by considering
a very wide range of refractive indices of the structure constituent materials,
we believe they can prove helpful in the design of future structures for the
control and the enhancement of the light-matter interaction.Comment: 8 pages, 6 figure
Local field enhancement: comparing self-similar and dimer nanoantennas
We study the local field enhancement properties of self-similar nanolenses
and compare the obtained results with the performance of standard dimer
nanoantennas. We report that, despite the additional structural complexity,
self-similar nanolenses are unable to provide significant improvements over the
field enhancement performance of standard plasmonic dimers
Off-resonance field enhancement by spherical nanoshells
We study light scattering by spherical nanoshells consistent of
metal/dielectric composites. We consider two geometries of metallic nanoshell
with dielectric core, and dielectric coated metallic nanoparticle. We
demonstrate that for both geometries the local field enhancement takes place
out of resonance regions ("dark states"), which, nevertheless, can be
understood in terms of the Fano resonance. At optimal conditions the light is
stronger enhanced inside the dielectric material. By using nonlinear dielectric
materials it will lead to a variety nonlinear phenomena applicable for
photonics applications
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