Search results for "Nonlinear"
showing 10 items of 3684 documents
Self-dressing and radiation reaction in classical electrodynamics
2002
A canonical approach to self-dressing in classical electrodynamics is presented. A slowly moving, rigid charge distribution is assumed to be completely deprived of the transverse electric E⊥ at an initial time t1' and the development of this component of the field is studied for t > t1' by solving the coupled charge-field Hamilton equations of motion. The theory is specialized to charge distributions of spherical symmetry, and in particular the point-charge, the spherical shell of charge and the spherical volume of charge are considered. As for the dynamics of the charge, the radiation-reaction force during self-dressing is obtained and it is shown to be substantially different at short tim…
Topological charge selection rule for phase singularities
2009
We present a study of the dynamics and decay pattern of phase singularities due to the action of a system with a discrete rotational symmetry of finite order. A topological charge conservation rule is identified. The role played by the underlying symmetry is emphasized. An effective model describing the short range dynamics of the vortex clusters has been designed. A method to engineer any desired configuration of clusters of phase singularities is proposed. Its flexibility to create and control clusters of vortices is discussed.
Nonlinear effects in charge stabilized colloidal suspensions
2006
Molecular Dynamics simulations are used to study the effective interactions in charged stabilized colloidal suspensions. For not too high macroion charges and sufficiently large screening, the concept of the potential of mean force is known to work well. In the present work, we focus on highly charged macroions in the limit of low salt concentrations. Within this regime, nonlinear corrections to the celebrated DLVO theory [B. Derjaguin and L. Landau, Acta Physicochem. USSR {\bf 14}, 633 (1941); E.J.W. Verwey and J.T.G. Overbeck, {\em Theory of the Stability of Lyotropic Colloids} (Elsevier, Amsterdam, 1948)] have to be considered. For non--bulklike systems, such as isolated pairs or triples…
Near-unity third-harmonic circular dichroism driven by a quasibound state in the continuum in asymmetric silicon metasurfaces
2021
We use numerical simulations to demonstrate third-harmonic generation with near-unity nonlinear circular dichroism (CD) and high conversion efficiency $({10}^{\ensuremath{-}2}\phantom{\rule{4pt}{0ex}}{\text{W}}^{\ensuremath{-}2})$ in asymmetric Si-on-$\mathrm{Si}{\mathrm{O}}_{2}$ metasurfaces. The working principle relies on the spin-selective excitation of a quasibound state in the continuum, characterized by a very high $(g{10}^{5})$ quality factor. By tuning multimode interference with the variation of the metasurface geometrical parameters, we show the possibility to control both linear CD and nonlinear CD. Our results pave the way for the development of all-dielectric metasurfaces for …
Universal description of pattern formation in optical oscillators under bichromatic injection
2018
We study pattern formation in a complex Swift–Hohenberg equation with phase-sensitive (parametric) gain. Such an equation serves as a universal order parameter equation describing the onset of spontaneous oscillations in extended systems submitted to a bichromatic injection when the instability is toward long (transverse) wavelengths. Applications include two-level lasers and photorefractive oscillators. Under such an injection, the original continuous phase symmetry of the system is replaced by a discrete one and phase bistability emerges. This leads to the spontaneous formation of phase-locked spatial structures, such as phase domains and dark-ring (phase) cavity solitons. The stability o…
Inelastic scattering and interactions of three-wave parametric solitons.
2006
We study the interactions of velocity-locked three-wave parametric solitons in a medium with quadratic nonlinearity and dispersion. We reveal that the inelastic scattering between three-wave solitons and linear waves may be described in terms of analytical solutions with dynamically varying group velocity, or boomerons. Moreover, we demonstrate the elastic nature of three-wave soliton-soliton collisions and interactions.
Line of polarization attraction in highly birefringent optical fibers
2014
We investigate the phenomenon of polarization attraction in a highly birefringent fiber. This polarization process originates from the nonlinear interaction of two counter-propagating beams. We show that all polarization states of the forward (signal) beam are attracted toward a specific line of polarization states on the surface of the Poincare sphere, whose characteristics are determined by the polarization state of the injected backward (pump) beam. This phenomenon of polarization attraction takes place without any loss of energy for the signal beam. The stability of different stationary solutions is also discussed through intensive numerical simulations. On the basis of mathematical tec…
From kinks to compactonlike kinks
1998
We show that, in the continuum limit, the generalized \ensuremath{\Phi}-four or double-well model with nonlinear coupling can exhibit compactonlike kink solutions for some specific velocity regimes and when the nonlinear coupling between pendulums is dominant. Our numerical simulations point out that the static compacton is stable and the dynamic compacton is unstable. Our study is extended to other topological systems where compacton solutions can also be found. A nice feature is that a mechanical analog of the double-well system can be constructed in the form of an experimental lattice of coupled pendulums, which, in the strong coupling limit, allows the observation of these entities.
Electro-optic time lens with an extended time aperture
2010
We propose what we believe to be a new approach to correct the residual aberrations of time lenses implemented through electro-optic sinusoidal phase modulation. The method is based on a single modulator driven with various harmonic channels coming from the same clock signal. Proper weighting of the amplitude and phase of the channels allows us to achieve nearly perfect parabolic phase modulation over a fraction of the clock period. We show numerically that our proposal only requires three harmonics of the clock frequency to achieve truly parabolic modulation over a time window that extends across 70% of the period. We illustrate the benefits of this aberration-free scheme in a pulse compre…
Experimental evidence of X-shaped spatiotemporal coherence of superfluorescence radiation
2006
Considering the parametric generation process in a quadratic nonlinear crystal, we report the experimental observation of optical waves characterized by a X-shaped spatiotemporal coherence, i.e. a coherence skewed along spatiotemporal trajectories.