79 research outputs found
Surface waves in mesh synthetic photonic lattices
Eigenmodes and dispersion curves in different configurations of synthetic photonic lattices are studied numerically. Eigenmodes localized on borders between areas with different optical potential are found. Stability of these eigenmodes against potential disturbances of different type is studied
Constructing eigenmode excitation spectrum in synthetic photonic lattices using optical heterodyning
A method based on optical heterodyning is proposed for measuring relative optical phases of pulses circulating in a synthetic photonic lattices. The knowledge of the phases can be further used for qualitative reconstruction of an eigenmode excitation spectrum in the synthetic photonic lattice
Spatiotemporal light localization in infiltrated waveguide arrays
We study light propagation in hexagonal waveguide arrays and show that simultaneous spatiotemporal localisation is possible by combination of engineered anomalous dispersion through selective excitation of Bloch-modes and spatial confinement in a nonlinear defect mode
Instabilities and Bifurcations of Nonlinear Impurity Modes
We study the structure and stability of nonlinear impurity modes in the
discrete nonlinear Schr{\"o}dinger equation with a single on-site nonlinear
impurity emphasizing the effects of interplay between discreteness,
nonlinearity and disorder. We show how the interaction of a nonlinear localized
mode (a discrete soliton or discrete breather) with a repulsive impurity
generates a family of stationary states near the impurity site, as well as
examine both theoretical and numerical criteria for the transition between
different localized states via a cascade of bifurcations.Comment: 8 pages, 8 figures, Phys. Rev. E in pres
Long-Range Coulomb Interaction and the Crossover between Quantum and Shot Noise in Diffusive Conductors
Frequency-dependent nonequilibrium noise in quantum-coherent diffusive
conductors is calculated with account taken of long-range Coulomb interaction.
For long and narrow contacts with strong external screening the crossover
between quantum and shot noise takes place at frequencies much smaller than the
voltage drop across the contact. We also show that under certain frequency
limitations, the semiclassical and quantum-coherent approaches to shot noise
are mathematically equivalent.Comment: 13 pages, RevTex, 7 ps figures, more details of derivation give
Nonlinear surface waves in left-handed materials
We study both linear and nonlinear surface waves localized at the interface
separating a left-handed medium (i.e. the medium with both negative dielectric
permittivity and negative magnetic permeability) and a conventional (or
right-handed) dielectric medium. We demonstrate that the interface can support
both TE- and TM-polarized surface waves - surface polaritons, and we study
their properties. We describe the intensity-dependent properties of nonlinear
surface waves in three different cases, i.e. when both the LH and RH media are
nonlinear and when either of the media is nonlinear. In the case when both
media are nonlinear, we find two types of nonlinear surface waves, one with the
maximum amplitude at the interface, and the other one with two humps. In the
case when one medium is nonlinear, only one type of surface wave exists, which
has the maximum electric field at the interface, unlike waves in right-handed
materials where the surface-wave maximum is usually shifted into a
self-focussing nonlinear medium. We discus the possibility of tuning the wave
group velocity in both the linear and nonlinear cases, and show that
group-velocity dispersion, which leads to pulse broadening, can be balanced by
the nonlinearity of the media, so resulting in soliton propagation.Comment: 9 pages, 10 figure
Qualitative aspects of the entanglement in the three-level model with photonic crystals
This communication is an enquiry into the circumstances under which
concurrence and phase entropy methods can give an answer to the question of
quantum entanglement in the composite state when the photonic band gap is
exhibited by the presence of photonic crystals in a three-level system. An
analytic approach is proposed for any three-level system in the presence of
photonic band gap. Using this analytic solution, we conclusively calculate the
concurrence and phase entropy, focusing particularly on the entanglement
phenomena. Specifically, we use concurrence as a measure of entanglement for
dipole emitters situated in the thin slab region between two semi-infinite
one-dimensionally periodic photonic crystals, a situation reminiscent of planar
cavity laser structures. One feature of the regime considered here is that
closed-form evaluation of the time evolution may be carried out in the presence
of the detuning and the photonic band gap, which provides insight into the
difference in the nature of the concurrence function for atom-field coupling,
mode frequency and different cavity parameters. We demonstrate how fluctuations
in the phase and number entropies effected by the presence of the
photonic-band-gap. The outcomes are illustrated with numerical simulations
applied to GaAs. Finally, we relate the obtained results to instances of any
three-level system for which the entanglement cost can be calculated. Potential
experimental observations in solid-state systems are discussed and found to be
promising.Comment: 28 pages, 10 figures: Accepted in Applied Physics B: Laser and Optic
Bose-Einstein Condensates in Optical Lattices: Band-Gap Structure and Solitons
We analyze the existence and stability of spatially extended (Bloch-type) and
localized states of a Bose-Einstein condensate loaded into an optical lattice.
In the framework of the Gross-Pitaevskii equation with a periodic potential, we
study the band-gap structure of the matter-wave spectrum in both the linear and
nonlinear regimes. We demonstrate the existence of families of spatially
localized matter-wave gap solitons, and analyze their stability in different
band gaps, for both repulsive and attractive atomic interactions
Nonlocal effects in the shot noise of diffusive superconductor - normal-metal systems
A cross-shaped diffusive system with two superconducting and two normal
electrodes is considered. A voltage is applied between the normal
leads. Even in the absence of average current through the superconducting
electrodes their presence increases the shot noise at the normal electrodes and
doubles it in the case of a strong coupling to the superconductors. The
nonequilibrium noise at the superconducting electrodes remains finite even in
the case of a vanishingly small transport current due to the absence of energy
transfer into the superconductors. This noise is suppressed by
electron-electron scattering at sufficiently high voltages.Comment: 4 pages, RevTeX, 2 eps figure
Discrete Nonlinear Schrodinger Equations Free of the Peierls-Nabarro Potential
We derive a class of discrete nonlinear Schr{\"o}dinger (DNLS) equations for
general polynomial nonlinearity whose stationary solutions can be found from a
reduced two-point algebraic problem. It is demonstrated that the derived class
of discretizations contains subclasses conserving classical norm or a modified
norm and classical momentum. These equations are interesting from the physical
standpoint since they support stationary discrete solitons free of the
Peierls-Nabarro potential. As a consequence, even in highly-discrete regimes,
solitons are not trapped by the lattice and they can be accelerated by even
weak external fields. Focusing on the cubic nonlinearity we then consider a
small perturbation around stationary soliton solutions and, solving
corresponding eigenvalue problem, we (i) demonstrate that solitons are stable;
(ii) show that they have two additional zero-frequency modes responsible for
their effective translational invariance; (iii) derive semi-analytical
solutions for discrete solitons moving at slow speed. To highlight the unusual
properties of solitons in the new discrete models we compare them with that of
the classical DNLS equation giving several numerical examples.Comment: Misprints noticed in the journal publication are corrected [in Eq.
(1) and Eq. (34)
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