764 research outputs found
Light capsules shaped by curvilinear meta-surfaces
We propose a simple yet efficient method for generating in-plane hollow beams
with a nearly-full circular light shell without the contribution of backward
propagating waves. The method relies on modulating the phase in the near field
of a centro-symmetric optical wavefront, such as that from a
high-numericalaperture focused wave field. We illustrate how beam acceleration
may be carried out by using an ultranarrow non-flat meta-surface formed by
engineered plasmonic nanoslits. A mirrorsymmetric, with respect to the optical
axis, circular caustic surface is numerically demonstrated that can be used as
an optical bottle
Stochastic theory of lineshape broadening in quasielastic He atom scattering with interacting adsorbates
The activated surface diffusion of interacting adsorbates is described in
terms of the so-called interacting single adsorbate approximation, which is
applied to the diffusion of Na atoms on Cu(001) for coverages up to 20% in
quasielastic He atom scattering experiments. This approximation essentially
consists of solving the standard Langevin equation with two noise sources and
frictions: a Gaussian white noise accounting for the friction with the
substrate, and a white shot noise characterized by a collisional friction
simulating the adsorbate-adsorbate collisions. The broadenings undergone by the
quasielastic peak are found to be in very good agreement with the experimental
data reported at two surface temperatures 200 and 300 K.Comment: 6 pages, 3 figure
Oblique surface waves at an interface of metal-dielectric superlattice and isotropic dielectric
We investigate the existence and the dispersion characteristics of surface
waves that propagate at an interface between metal-dielectric superlattice and
isotropic dielectric. Within the long wavelength limit, when the
effective-medium approximation is valid, the superlattice behaves like a
uniaxial plasmonic crystal with the main optical axes perpendicular to the
metal-dielectric interfaces. We demonstrate that if such a semi-infinite
plasmonic crystal is cut normally to the layer interfaces and brought into the
contact with semi-infinite dielectric, a new type of surface modes can appear.
The propagation of such modes obliquely to the optical axes occurs under
favorable conditions that regard thicknesses of the layers, as well as the
proper choice of dielectric permittivity of the constituent materials. We show
that losses within the metallic layers can be substantially reduced by making
the layers sufficiently thin. At the same time, a dramatic enlargement of the
range of angles for oblique propagation of the new surface modes is observed.
This can lead, however, to the field non-locality and consequently to the
failure of the effective-medium approximation.Comment: 4 pages, 3 figure
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