13,454 research outputs found
Interface solitons in quadratically nonlinear photonic lattices
We study the properties of two-color nonlinear localized modes which may
exist at the interfaces separating two different periodic photonic lattices in
quadratic media, focussing on the impact of phase mismatch of the photonic
lattices on the properties, stability, and threshold power requirements for the
generation of interface localized modes. We employ both an effective discrete
model and continuum model with periodic potential and find good qualitative
agreement between both models. Dynamics excitation of interface modes shows
that, a two-color interface twisted mode splits into two beams with different
escaping angles and carrying different energies when entering a uniform medium
from the quadratic photonic lattice. The output position and energy contents of
each two-color interface solitons can be controlled by judicious tuning ofComment: 6 pages, 8 figure
Interface solitons in two-dimensional photonic lattices
We analyze localization of light at the interface separating square and
hexagonal photonic lattices, as recently realized experimentally in
two-dimensional laser-written waveguide arrays in silica glass with
self-focusing nonlinearity [A. Szameit {\em et al.}, Opt. Lett. {\bf 33}, 663
(2008)]. We reveal the conditions for the existence of {\em linear} and {\em
nonlinear} surface states substantially influenced by the lattice topology, and
study the effect of the different symmetries and couplings on the stability of
two-dimensional interface solitons.Comment: 3 pages, 4 figures, submitted to Opt. Let
Two-color discrete localized modes and resonant scattering in arrays of nonlinear quadratic optical waveguides
We analyze the properties and stability of two-color discrete localized modes
in arrays of channel waveguides where tunable quadratic nonlinearity is
introduced as a nonlinear defect by periodic poling of a single waveguide in
the array. We show that, depending on the value of the phase mismatch and the
input power, such two-color defect modes can be realized in three different
localized states. We also study resonant light scattering in the arrays with
the defect waveguide.Comment: 10 pages, 3 figures, published in PR
Localized modes and bistable scattering in nonlinear network junctions
We study the properties of junctions created by crossing of N identical
branches of linear discrete networks. We reveal that for N>2 such a junction
creates a topological defect and supports two types of spatially localized
modes. We analyze the wave scattering by the junction defect and demonstrate
nonzero reflection for any set of parameters. If the junction is nonlinear, it
is possible to achieve the maximum transmission for any frequency by tuning the
intensity of the scattering wave. In addition, near the maximum transmission
the system shows the bistable behaviour.Comment: 5 pages, 7 figures, submitted to Physical Review
Interface localized modes and hybrid lattice solitons in waveguide arrays
We discuss the formation of guided modes localized at the interface separat-
ing two different periodic photonic lattices. Employing the effective discrete
model, we analyze linear and nonlinear interface modes and also predict the
existence of stable interface solitons including the hybrid
staggered/unstaggered lattice solitons with the tails belonging to spectral
gaps of different types.Comment: 11 pages, 5 figures, submitted to Opt. Let
Scaling of entanglement between separated blocks in spin chains at criticality
We compute the entanglement between separated blocks in certain spin models
showing that at criticality this entanglement is a function of the ratio of the
separation to the length of the blocks and can be written as a product of a
power law and an exponential decay. It thereby interpolates between the
entanglement of individual spins and blocks of spins. It captures features of
correlation functions at criticality as well as the monogamous nature of
entanglement. We exemplify invariant features of this entanglement to
microscopic changes within the same universality class. We find this
entanglement to be invariant with respect to simultaneous scale transformations
of the separation and the length of the blocks. As a corollary, this study
estimates the entanglement between separated regions of those quantum fields to
which the considered spin models map at criticality.Comment: 4 pages, 3 figures; comments welcom
Multistability and localization in coupled nonlinear split-ring resonators
We study the dynamics of a pair of nonlinear split-ring resonators (a
`metadimer') excited by an alternating magnetic field and coupled magnetically.
Linear metadimers of this kind have been recently used as the elementary
components for three-dimensional metamaterials or 'stereometamaterials' [N. Liu
{\em et al}, Nature Photon. {\bf 3}, 157 (2009)]. We demonstrate that
nonlinearity offers more possibilities with respect to real-time tunability and
a multiplicity of states which can be reached by varying the external field.
Moreover, we demonstrate almost total localization of the energy in one of the
resonators in a broad range of parameters.Comment: 3 pages, 5 figure
Surface solitons in two-dimensional chirped photonic lattices
We study surface modes in semi-infinite chirped two-dimensional photonic
lattices in the frame- work of an effective discrete nonlinear model. We
demonstrate that the lattice chirp can change dramatically the conditions for
the mode localization near the surface, and we find numerically the families of
surface modes, in linear lattices, and discrete surface solitons, in nonlinear
lattices. We demonstrate that, in a sharp contrast to one-dimensional discrete
surface solitons, in two-dimensional lattices the mode threshold power is
lowered by the action of both the surface and lattice chirp. By manipulating
with the lattice chirp, we can control the mode position and its localization.Comment: 12 pages, 7 figure
Fano resonance in quadratic waveguide arrays
We study resonant light scattering in arrays of channel optical waveguides
where tunable quadratic nonlinearity is introduced as nonlinear defects by
periodic poling of single (or several) waveguides in the array. We describe
novel features of wave scattering that can be observed in this structure and
show that it is a good candidate for the first observation of Fano resonance in
nonlinear optics.Comment: 3 pages, 3 figures, submitted to Optics Letters, slightly revise
Discrete surface solitons in two-dimensional anisotropic photonic lattices
We study nonlinear surface modes in two-dimensional {\em anisotropic}
periodic photonic lattices and demonstrate that, in a sharp contrast to
one-dimensional discrete surface solitons, the mode threshold power is lower at
the surface, and two-dimensional discrete solitons can be generated easier near
the lattice corners and edges. We analyze the crossover between effectively
one- and two-dimensional regimes of the surface-mediated beam localization in
the lattice.Comment: 3 pages, 4 figure
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