104 research outputs found
Negative-Index Metamaterials: Second-Harmonic Generation, Manley-Rowe Relations and Parametric Amplification
Second harmonic generation and optical parametric amplification in
negative-index metamaterials (NIMs) are studied. The opposite directions of the
wave vector and the Poynting vector in NIMs results in a "backward"
phase-matching condition, causing significant changes in the Manley-Rowe
relations and spatial distributions of the coupled field intensities. It is
shown that absorption in NIMs can be compensated by backward optical parametric
amplification. The possibility of distributed-feedback parametric oscillation
with no cavity has been demonstrated. The feasibility of the generation of
entangled pairs of left- and right-handed counter-propagating photons is
discussed.Comment: 7 pages, 6 figure
Quantum interference in nanofractals and its optical manifestation
We consider quantum interferences of ballistic electrons propagating inside
fractal structures with nanometric size of their arms. We use a scaling
argument to calculate the density of states of free electrons confined in a
simple model fractal. We show how the fractal dimension governs the density of
states and optical properties of fractal structures in the RF-IR region. We
discuss the effect of disorder on the density of states along with the
possibility of experimental observation.Comment: 19 pages, 6 figure
Second Harmonic Generation for a Dilute Suspension of Coated Particles
We derive an expression for the effective second-harmonic coefficient of a
dilute suspension of coated spherical particles. It is assumed that the coating
material, but not the core or the host, has a nonlinear susceptibility for
second-harmonic generation (SHG). The resulting compact expression shows the
various factors affecting the effective SHG coefficient. The effective SHG per
unit volume of nonlinear coating material is found to be greatly enhanced at
certain frequencies, corresponding to the surface plasmon resonance of the
coated particles. Similar expression is also derived for a dilute suspension of
coated discs. For coating materials with third-harmonic (THG) coefficient,
results for the effective THG coefficients are given for the cases of coated
particles and coated discs.Comment: 11 pages, 3 figures; accepted for publication in Phys. Rev.
Controlling Silver Nanoparticle Size and Morphology with Photostimulated Synthesis
Photo-induced synthesis and control over the size and shape of colloidal
silver nanoparticles is investigated in contrast to photo-stimulated
aggregation of small nanoparticles into large fractal-type structures. The
feasibility of light-driven nanoengineering which enables manipulation of the
sizes and shapes of the isolated nanoparticles is studied by varying the amount
and type of the stabilizing agent and the type of optical irradiation.Comment: 10 pages, 7 figures, 11 image
Dimensional Crossover in the Effective Second Harmonic Generation of Films of Random Dielectrics
The effective nonlinear response of films of random composites consisting of
a binary composite with nonlinear particles randomly embedded in a linear host
is theoretically and numerically studied. A theoretical expression for the
effective second harmonic generation susceptibility, incorporating the
thickness of the film, is obtained by combining a modified effective-medium
approximation with the general expression for the effective second harmonic
generation susceptibility in a composite. The validity of the thoretical
results is tested against results obtained by numerical simulations on random
resistor networks. Numerical results are found to be well described by our
theory. The result implies that the effective-medium approximation provides a
convenient way for the estimation of the nonlinear response in films of random
dielectrics.Comment: 9 pages, 2 figures; accepted for publication in Phys. Rev.
Fabricating plasmonic components for nanophotonics:[invited]
We report on experimental realization of different metal-dielectric structures that are used as surface plasmon polariton waveguides and as plasmonic metamaterials. Fabrication approaches based on different lithographic and deposition techniques are discussed
A concentration phenomenon for semilinear elliptic equations
For a domain \Omega\subset\dR^N we consider the equation -\Delta u +
V(x)u = Q_n(x)\abs{u}^{p-2}u with zero Dirichlet boundary conditions and
. Here and are bounded functions that are positive
in a region contained in and negative outside, and such that the sets
shrink to a point as . We show that if
is a nontrivial solution corresponding to , then the sequence
concentrates at with respect to the and certain
-norms. We also show that if the sets shrink to two points and
are ground state solutions, then they concentrate at one of these points
Solitary wave solution to the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability
We present a solitary wave solution of the generalized nonlinear Schrodinger
equation for dispersive permittivity and permeability using a scaling
transformation and coupled amplitude-phase formulation. We have considered the
third-order dispersion effect (TOD) into our model and show that soliton shift
may be suppressed in a negative index material by a judicious choice of the TOD
and self-steepening parameter.Comment: 6 page
Resonant nonlinear optics of backward waves in negative-index metamaterials
The extraordinary properties of resonant four-wave mixing of backward waves
in doped negative-index materials are investigated. The feasibility of
independent engineering of negative refractive index and nonlinear optical
response as well as quantum control of the nonlinear propagation process in
such composites is shown due to the coherent energy transfer from the control
to the signal field. Laser-induced transparency, quantum switching,
frequency-tunable narrow-band filtering, amplification, and realizing a
miniature mirrorless optical parametric generator of the entangled backward and
ordinary waves are among the possible applications of the investigated
processes.Comment: 10 pages, 9 figure
Frequency-dependent (ac) Conduction in Disordered Composites: a Percolative Study
In a recent paper [Phys. Rev. B{\bf57}, 3375 (1998)], we examined in detail
the nonlinear (electrical) dc response of a random resistor cum tunneling bond
network (, introduced by us elsewhere to explain nonlinear response of
metal-insulator type mixtures). In this work which is a sequel to that paper,
we consider the ac response of the -based correlated () model.
Numerical solutions of the Kirchoff's laws for the model give a power-law
exponent (= 0.7 near ) of the modulus of the complex ac conductance at
moderately low frequencies, in conformity with experiments on various types of
disordered systems. But, at very low frequencies, it gives a simple quadratic
or linear dependence on the frequency depending upon whether the system is
percolating or not. We do also discuss the effective medium approximation
() of our and the traditional random network model, and discuss
their comparative successes and shortcomings.Comment: Revised and reduced version with 17 LaTeX pages plus 8 JPEG figure
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