85 research outputs found
Spatially incoherent modulational instability in a non local medium
We investigate one-dimensional transverse modulational instability in a non
local medium excited with a spatially incoherent source. Employing undoped
nematic liquid crystals in a planar pre-tilted configuration, we investigate
the role of the spectral broadening induced by incoherence in conjunction with
the spatially non local molecular reorientation. The phenomenon is modeled
using the Wigner transform.Comment: 13 pages with 4 figures included. To be published in Laser Physics
Letter
All-optical switching in lithium niobate directional couplers with cascaded nonlinearity
We report on intensity-dependent switching in lithium niobate directional couplers. Large nonlinear phase shifts that are due to cascading detune the coupling between the coupler branches, which makes all-optical switching possible. Depending on the input intensity, the output could be switched between the cross and the bar coupler branches with a switching ratio of 1:5 and a throughput of 80%
Frequency down conversion through Bose condensation of light
We propose an experimental set up allowing to convert an input light of
wavelengths about into an output light of a lower frequency. The
basic principle of operating relies on the nonlinear optical properties
exhibited by a microcavity filled with glass. The light inside this material
behaves like a 2D interacting Bose gas susceptible to thermalise and create a
quasi-condensate. Extension of this setup to a photonic bandgap material (fiber
grating) allows the light to behave like a 3D Bose gas leading, after
thermalisation, to the formation of a Bose condensate. Theoretical estimations
show that a conversion of into is achieved with an input
pulse of about with a peak power of , using a fiber grating
containing an integrated cavity of size about .Comment: 4 pages, 1 figure
Soliton molecules in trapped vector Nonlinear Schrodinger systems
We study a new class of vector solitons in trapped Nonlinear Schrodinger
systems modelling the dynamics of coupled light beams in GRIN Kerr media and
atomic mixtures in Bose-Einstein condensates. These solitons exist for
different spatial dimensions, their existence is studied by means of a
systematic mathematical technique and the analysis is made for inhomogeneous
media
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
Stable vortex and dipole vector solitons in a saturable nonlinear medium
We study both analytically and numerically the existence, uniqueness, and
stability of vortex and dipole vector solitons in a saturable nonlinear medium
in (2+1) dimensions. We construct perturbation series expansions for the vortex
and dipole vector solitons near the bifurcation point where the vortex and
dipole components are small. We show that both solutions uniquely bifurcate
from the same bifurcation point. We also prove that both vortex and dipole
vector solitons are linearly stable in the neighborhood of the bifurcation
point. Far from the bifurcation point, the family of vortex solitons becomes
linearly unstable via oscillatory instabilities, while the family of dipole
solitons remains stable in the entire domain of existence. In addition, we show
that an unstable vortex soliton breaks up either into a rotating dipole soliton
or into two rotating fundamental solitons.Comment: To appear in Phys. Rev.
Resonance solitons produced by azimuthal modulation in self-focusing and self-defocusing materials
THE OPTICS OF SURFACE PLASMONS
On étudie l'incidence de plasmons de surface ou de champs de rayonnement (a) sur le bord d'une surface adaptée à la propagation d'un plasmon de surface et (b) sur une barrière de largeur variable entre deux telles surfaces, et on calcule numériquement la réflexion, la transmission et la conversion en champ de rayonnement. Nous utilisons dans notre modèle deux plans conducteurs au dessus et au dessous de la surface de propagation pour limiter le nombre de modes de propagation.We have studied numerically the reflection, transmission, and conversion to radiation fields of surface polaritons or radiation fields incident (a) onto the end face of a polariton active medium or (b) from one polariton active medium to another separated by a variable width barrier. This problem was modeled by placing shorting planes above and below the propagation surface to limit to a discrete number the propagating modes
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