Search results for "Instability"
showing 10 items of 724 documents
Chaotic-like behavior of modulated waves in a nonlinear discrete LC transmission line
2003
International audience; Modulational instability (MI) in a discrete nonlinear LC transmission line is investigated. The higher order nonlinear Schrodinger (NLS) equation modeling modulated waves propagation in the network allows to predict the MI conditions, with additional features, compared to the standard NLS model. More precisely, a chaotic-like behavior of the system, which is observed in a particular frequency domain, is related to the nonrepeatability of the numerical experiments.
Polarization instability in anisotropic-cavity degenerate four-wave mixing
2000
Abstract The emission and stability properties of a plane-wave model of intracavity degenerate four-wave mixing including self- and cross-phase modulation are studied. A Kerr medium inside an anisotropic cavity in which a linearly polarized field is injected is considered. Cavity anisotropy leads to qualitative new phenomena such as a subcritical polarization instability.
Modulation instability scenario in negative index materials
2010
We present an investigation of the critical frequency windows permitting modulation instability in negative index materials. The principal motivation for our analysis stems from the impact of the inevitable presence of the effective dispersive magnetic permeability in addition to the effective dielectric permittivity determining the propagation model for ultrashort pulses in negative index materials. We emphasize the influence of nonlinear dispersion terms, arising out of the combinatorial effect of the dispersive permeability with the nonlinear polarization, over the MI phenomena, the outcome of its development achieved by using linear stability analysis. Gain spectrum investigation has be…
Gap solitons and modulation instability in a dynamic Bragg grating with nonlinearity management
2008
International audience; We investigate the occurrence of modulation instability in systems in which a dynamic Bragg grating consists of alternating positive and negative Kerr coefficients. The dependence of modulation instability gain spectra over the perturbation wavenumber and system parameters is portrayed near and at the edges of the photonic band gap structure. Further, we demonstrate the generation of traveling gap solitons near the photonic band gap structure through the modulation instability
Laser instabilities in a Gaussian cavity mode with Gaussian pump profile
1998
We analytically demonstrate that both single-mode and multimode instabilities may occur in a Gaussian-cavity-mode laser model with Gaussian pump profile. As a necessary condition, the ratio of the beam waist to the pump waist must exceed a given limiting value, which depends on the population decay rate. For an infinitely concentrated pump the plane-wave model instability thresholds are recovered, and there exists an optimum value of the waists ratio for which the second laser threshold is minimum.
Lorenz–Haken instability in a laser with arbitrary mirrors reflectivity
2000
Abstract We study the Lorenz–Haken instability in a laser with arbitrary mirrors reflectivity R . In the limit of slow population difference we demonstrate that in order to observe the instability the reflectivity must exceed the critical value R c ≃0.5379, which coincides with that found recently for the multimode (Risken–Nummedal–Graham–Haken) instability. Several other differences with respect to the uniform field limit R →1 are presented.
Instabilities of four-wave mixing
2005
We predict that four-wave mixing driven by a dual frequency input undergoes different instability scenarios encompassing modulational instability or multiple shock formation in the anomalous and normal dispersion regime, respectively.
Closed Busse balloon for rolls and skew-varicose instability in a Swift-Hohenberg model with nonlinear resonance
1998
Abstract A Swift-Hohenberg model incorporating a nonlinear resonance is shown to produce stable rolls only in a closed region of the parameter space. This Busse balloon is limited by zigzag and Eckhaus boundaries. A skew-varicose instability outside the balloon also exists. Implications with nonlinear optics and hydrodynamic convection are commented.
Self-consistent subduction initiation induced by mantle flow
2015
Mantle circulation in planets with strongly temperature-dependent viscosity results in stagnant-lid convection. It is fundamental to understand how this stagnant-lid regime can change into a plate-like convection regime as on the present-day Earth. Here, we use 2D numerical models to study subduction initiation from an initial stagnant lid with laboratory-consistent parameters and without pre-existing weak zones or kinematic boundary conditions. Our results show that subduction can be initiated dynamically as a result of a thermal localization instability. The lithosphere may deform in a stagnant-lid mode, an un-necking mode, a symmetric-subduction mode or an asymmetric-subduction mode. The…
Linear and non-linear stability of a thermally stratified magnetically driven rotating flow in a cylinder
2010
The stability of a thermally stratified liquid metal flow is considered numerically. The flow is driven by the rotating magnetic field in a cylinder heated from above and cooled from below. The stable thermal stratification turns out to destabilise the flow. This is explained by the fact that a stable stratification suppresses the secondary meridional flow, thus indirectly enhancing the primary rotation. The instability in the form of Taylor-Görtler rolls is consequently promoted. It is known from earlier studies that these rolls can be only excited by finite disturbances in the isothermal flow. A sufficiently strong thermal stratification transforms this non-linear bypass instability into …