213 research outputs found
Theory of nonlocal soliton interaction in nematic liquid crystals
We investigate interactions between spatial nonlocal bright solitons in nematic liquid crystals using an analytical (“effective particle”) approach as well as direct numerical simulations. The model predicts attraction of out-of-phase solitons and the existence of their stable bound state. This nontrivial property is solely due to the nonlocal nature of the nonlinear response of the liquid crystals. We further predict and verify numerically the critical outwards angle and degree of nonlocality which determine the transition between attraction and repulsion of out-of-phase solitons
Nonlocal stabilization of nonlinear beams in a self-focusing atomic vapor
We show that ballistic transport of optically excited atoms in an atomic
vapor provides a nonlocal nonlinearity which stabilizes the propagation of
vortex beams and higher order modes in the presence of a self-focusing
nonlinearity. Numerical experiments demonstrate stable propagation of lowest
and higher order vortices over a hundred diffraction lengths, before
dissipation leads to decay of these structures.Comment: 3 figure
Modulational instability, solitons and beam propagation in spatially nonlocal nonlinear media
We present an overview of recent advances in the understanding of optical
beams in nonlinear media with a spatially nonlocal nonlinear response. We
discuss the impact of nonlocality on the modulational instability of plane
waves, the collapse of finite-size beams, and the formation and interaction of
spatial solitons.Comment: Review article, will be published in Journal of Optics B, special
issue on Optical Solitons, 6 figure
Scattering of dipole-mode vector solitons: Theory and experiment
We study, both theoretically and experimentally, the scattering properties of
optical dipole-mode vector solitons - radially asymmetric composite
self-trapped optical beams. First, we analyze the soliton collisions in an
isotropic two-component model with a saturable nonlinearity and demonstrate
that in many cases the scattering dynamics of the dipole-mode solitons allows
us to classify them as ``molecules of light'' - extremely robust spatially
localized objects which survive a wide range of interactions and display many
properties of composite states with a rotational degree of freedom. Next, we
study the composite solitons in an anisotropic nonlinear model that describes
photorefractive nonlinearities, and also present a number of experimental
verifications of our analysis.Comment: 8 pages + 4 pages of figure
Two dimensional modulational instability in photorefractive media
We study theoretically and experimentally the modulational instability of
broad optical beams in photorefractive nonlinear media. We demonstrate the
impact of the anisotropy of the nonlinearity on the growth rate of periodic
perturbations. Our findings are confirmed by experimental measurements in a
strontium barium niobate photorefractive crystal.Comment: 8 figure
A new approach to the relativistic treatment of the fermion-boson system, based on the extension of the SL(2,C) group
A new technique for constructing the relativistic wave equation for the
two-body system composed of the spin-1/2 and spin-0 particles is proposed. The
method is based on the extension of the SL(2,C) group to the Sp(4,C) one. The
obtained equation includes the interaction potentials, having both the
Lorentz-vector and Lorentz-tensor structure, exactly describes the relativistic
kinematics and possesses the correct one-particle limits. The comparison with
results of other approaches to this problem is discussed.Comment: v3: revised version (to appear in Mod. Phys. Lett. A
Linear and nonlinear waveguides induced by optical vortex solitons
We study, numerically and analytically, linear and nonlinear waveguides
induced by optical vortex solitons in a Kerr medium. Both fundamental and
first-order guided modes are analyzed, as well as the cases of effectively
defocusing and focusing nonlinearity.Comment: 3 pages, 3 figures, changed conten
Interaction of matter-wave gap solitons in optical lattices
We study mobility and interaction of gap solitons in a Bose-Einstein
condensate (BEC) confined by an optical lattice potential. Such localized
wavepackets can exist only in the gaps of the matter-wave band-gap spectrum and
their interaction properties are shown to serve as a measure of discreteness
imposed onto a BEC by the lattice potential. We show that inelastic collisions
of two weakly localized near-the-band-edge gap solitons provide simple and
effective means for generating strongly localized in-gap solitons through
soliton fusion.Comment: 12 pages, 7 figure
The theory of optical dispersive shock waves in photorefractive media
The theory of optical dispersive shocks generated in propagation of light
beams through photorefractive media is developed. Full one-dimensional
analytical theory based on the Whitham modulation approach is given for the
simplest case of sharp step-like initial discontinuity in a beam with
one-dimensional strip-like geometry. This approach is confirmed by numerical
simulations which are extended also to beams with cylindrical symmetry. The
theory explains recent experiments where such dispersive shock waves have been
observed.Comment: 26 page
A Potential of Interaction between Two- and Three-Dimensional Solitons
A general method to find an effective potential of interaction between far
separated 2D and 3D solitons is elaborated, including the case of 2D vortex
solitons. The method is based on explicit calculation of the overlapping term
in the full Hamiltonian of the system (_without_ assuming that the ``tail'' of
each soliton is not affected by its interaction with the other soliton, and, in
fact,_without_ knowing the exact form of the solution for an isolated soliton -
the latter problem is circumvented by reducing a bulk integral to a surface
one). The result is obtained in an explicit form that does not contain an
artificially introduced radius of the overlapping region. The potential applies
to spatial and spatiotemporal solitons in nonlinear optics, where it may help
to solve various dynamical problems: collisions, formation of bound states
(BS's), etc. In particular, an orbiting BS of two solitons is always unstable.
In the presence of weak dissipation and gain, the effective potential can also
be derived, giving rise to bound states similar to those recently studied in 1D
models.Comment: 29 double-spaced pages in the latex format and 1 figure in the ps
format. The paper will appear in Phys. Rev.
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