28 research outputs found
Cloaking due to anomalous localized resonance in plasmonic structures of confocal ellipses
If a core of dielectric material is coated by a plasmonic structure of
negative dielectric material with non-zero loss parameter, then anomalous
localized resonance may occur as the loss parameter tends to zero and the
source outside the structure can be cloaked. It has been proved that the
cloaking due to anomalous localized resonance (CALR) takes place for structures
of concentric disks and the critical radius inside which the sources are
cloaked has been computed. In this paper, it is proved that CALR takes place
for structures of confocal ellipses and the critical elliptic radii are
computed. The method of this paper uses the spectral analysis of the
Neumann-Poincar\'e type operator associated with two interfaces (the boundaries
of the core and the shell)
Analytical results regarding electrostatic resonances of surface phonon/plasmon polaritons: separation of variables with a twist
The boundary integral equation method ascertains explicit relations between
localized surface phonon and plasmon polariton resonances and the eigenvalues
of its associated electrostatic operator. We show that group-theoretical
analysis of Laplace equation can be used to calculate the full set of
eigenvalues and eigenfunctions of the electrostatic operator for shapes and
shells described by separable coordinate systems. These results not only unify
and generalize many existing studies but also offer the opportunity to expand
the study of phenomena like cloaking by anomalous localized resonance. For that
reason we calculate the eigenvalues and eigenfunctions of elliptic and circular
cylinders. We illustrate the benefits of using the boundary integral equation
method to interpret recent experiments involving localized surface phonon
polariton resonances and the size scaling of plasmon resonances in graphene
nano-disks. Finally, symmetry-based operator analysis can be extended from
electrostatic to full-wave regime. Thus, bound states of light in the continuum
can be studied for shapes beyond spherical configurations.Comment: 25 pages, 3 figures, to be published Proc. Royal Soc.
On Absence and Existence of the Anomalous Localized Resonance without the Quasi-static Approximation
The paper considers the transmission problems for Helmholtz equation with
bodies that have negative material parameters. Such material parameters are
used to model metals on optical frequencies and so-called metamaterials. As the
absorption of the materials in the model tends to zero the fields may blow up.
When the speed of the blow up is suitable, this is called the Anomalous
Localized Reconance (ALR). In this paper we study this phenomenon and formulate
a new condition, the weak Anomalous Localized Reconance (w-ALR), where the
speed of the blow up of fields may be slower. Using this concept, we can study
the blow up of fields in the presence of negative material parameters without
the commonly used quasi-static approximation. We give simple geometric
conditions under which w-ALR or ALR may, or may not appear. In particular, we
show that in a case of a curved layer of negative material with a strictly
convex boundary neither ALR nor w-ALR appears with non-zero frequencies (i.e.
in the dynamic range) in dimensions . In the case when the boundary of
the negative material contains a flat subset we show that the w-ALR always
happens with some point sources in dimensions . These results, together
with the earlier results of Milton et al. ( [22, 23]) and Ammari et al. ([2])
show that for strictly convex bodies ALR may appear only for bodies so small
that the quasi-static approximation is realistic. This gives limits for size of
the objects for which invisibility cloaking methods based on ALR may be used.Comment: 30 pages, 7 figure