130 research outputs found
Nonlocal Optics of Plasmonic Nanowire Metamaterials
We present an analytical description of the nonlocal optical response of
plasmonic nanowire metamaterials that enable negative refraction, subwavelength
light manipulation, and emission lifetime engineering. We show that dispersion
of optical waves propagating in nanowire media results from coupling of
transverse and longitudinal electromagnetic modes supported by the composite
and derive the nonlocal effective medium approximation for this dispersion. We
derive the profiles of electric field across the unit cell, and use these
expressions to solve the long-standing problem of additional boundary
conditions in calculations of transmission and reflection of waves by nonlocal
nanowire media. We verify our analytical results with numerical solutions of
Maxwell's equations and discuss generalization of the developed formalism to
other uniaxial metamaterials
Cut-wire-pair structures as two-dimensional magnetic metamaterials
We study numerically and experimentally magnetic metamaterials based on
cut-wire pairs instead of split-ring resonators. The cut-wire pair planar
structure is extended in order to create a truly two-dimensional metamaterial
suitable for scaling to optical frequencies. We fabricate the cut-wire
metamaterial operating at microwave frequencies with lattice spacing around 10%
of the free-space wavelength, and find good agreement with direct numerical
simulations. Unlike the structures based on split-ring resonators, the
nearest-neighbor coupling in cut-wire pairs can result in a magnetic stop-band
with propagation in the transverse direction
Non-magnetic left-handed material
We develop a new approach to build a material with negative refraction index.
In contrast to conventional designs which make use of a resonant behavior to
achieve a non-zero magnetic response, our material is intrinsically
non-magnetic and relies on an anisotropic dielectric constant to provide a
left-handed response in waveguide geometry. We demonstrate that the proposed
material can support surface (polariton) waves, and show the connection between
polaritons and the enhancement of evanescent fields, also referred to as
super-lensing
A Superlens Based on Metal-Dielectric Composites
Pure noble metals are typically considered to be the materials of choice for
a near-field superlens that allows subwavelength resolution by recovering both
propagating and evanescent waves. However, a superlens based on bulk metal can
operate only at a single frequency for a given dielectric host. In this Letter,
it is shown that a composite metal-dielectric film, with an appropriate metal
filling factor, can operate at practically any desired wavelength in the
visible and near-infrared ranges. Theoretical analysis and simulations verify
the feasibility of the proposed lens.Comment: 15 pages, 4 figure
Propagation of Surface Plasmons in Ordered and Disordered Chains of Metal Nanospheres
We report a numerical investigation of surface plasmon (SP) propagation in
ordered and disordered linear chains of metal nanospheres. In our simulations,
SPs are excited at one end of a chain by a near-field tip. We then find
numerically the SP amplitude as a function of propagation distance. Two types
of SPs are discovered. The first SP, which we call the ordinary or quasistatic,
is mediated by short-range, near-field electromagnetic interaction in the
chain. This excitation is strongly affected by Ohmic losses in the metal and by
disorder in the chain. These two effects result in spatial decay of the
quasistatic SP by means of absorptive and radiative losses, respectively. The
second SP is mediated by longer range, far-field interaction of nanospheres. We
refer to this SP as the extraordinary or non-quasistatic. The non-quasistatic
SP can not be effectively excited by a near-field probe due to the small
integral weight of the associated spectral line. Because of that, at small
propagation distances, this SP is dominated by the quasistatic SP. However, the
non-quasistatic SP is affected by Ohmic and radiative losses to a much smaller
extent than the quasistatic one. Because of that, the non-quasistatic SP
becomes dominant sufficiently far from the exciting tip and can propagate with
little further losses of energy to remarkable distances. The unique physical
properties of the non-quasistatic SP can be utilized in all-optical integrated
photonic systems
Magnetoinductive breathers in magnetic metamaterials
The existence and stability of discrete breathers (DBs) in one-dimensional
and two-dimensional magnetic metamaterials (MMs), which consist of periodic
arrangem ents (arrays) of split-ring resonators (SRRs), is investigated
numerically. We consider different configurations of the SRR arrays, which are
related to the relative orientation of the SRRs in the MM, both in one and two
spatial dimensions. In the latter case we also consider anisotropic MMs. Using
standard numerical methods we construct several types of linearly stable
breather excitations both in Hamiltonian and dissipative MMs (dissipative
breathers). The study of stability in both cases is performed using standard
Floquet analysi s. In both cases we found that the increase of dimensionality
from one to two spatial dimensions does not destroy the DBs, which may also
exist in the case of moderate anisotropy (in two dimensions). In dissipative
MMs, the dynamics is governed by a power balance between the mainly Ohmic
dissipation and driving by an alternating magnetic field. In that case it is
demonstrated that DB excitation locally alters the magnetic response of MMs
from paramagnetic to diamagnetic. Moreover, when the frequency of the applied
field approaches the SRR resonance frequency, the magnetic response of the MM
in the region of the DB excitation may even become negative (extreme
diamagnetic).Comment: 12 pages 15 figure
A novel graph decomposition approach to the automatic processing of poorly formalized data : innovative ideas : a management case study
In the following paper we present a novel approach to unstructured data processing by imposing a hierarchical graph-based structure on the data and decomposing it into separate subgraphs according to optimization criteria. In the scope of the paper we also consider the problem of automatic classification of textual data for the synthesizing the hierarchical data structure. The proposed approach uses textual information on the first stage to classify ideas, innovations, and objects of intellectual property (OIPs) to construct a multilayered graph. Numerical criteria are used to decompose constructed graph into separate subgraphs. In the scope of the research we apply the developed approach to the innovative ideas in a management case study. The research has been conducted in the scope of a joint research project with financial aid of Ministry of Education and Science of Russian Federation RFMEFI57314X0007.peer-reviewe
Far field imaging by a planar lens: diffraction versus superresolution
We resolve the long standing controversy regarding the imaging by a planar
lens made of left-handed media and demonstrate theoretically that its far field
image has a fundamentally different origin depending on the relationship
between losses {inside} the lens and the wavelength of the light . At
small enough the image is always governed by diffraction theory, and
the resolution is independent of the absorption if both Im and
Im. For any finite , however, a critical absorption exists
below which the superresolution regime takes place, though this absorption is
extremely low and can hardly be achieved. We demonstrate that the transition
between diffraction limited and superresolution regimes is governed by {the}
universal parameter combining absorption, wavelength, and lens thickness.
Finally, we show that this parameter is related to the resonant excitation of
the surface plasma waves
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