Search results for "Nonlinear"
showing 10 items of 3684 documents
Stochastic Kinetics with Wave Nature
2003
We consider stochastic second-order partial differential equations. We indroduce a noisy non-linear wave equation and discuss its connections, in particular via the Lorentz transformation, with known stochastic models.
Noise effects on gap wave propagation in a nonlinear discrete LC transmission line
2007
International audience; We report here the results of numerical investigation of noise effects on the propagation in a nonlinear waveguide modeled by a discrete electrical line. Considering a periodic signal of frequency exceeding the natural cutoff frequency of this system, we show that noise can be used to trigger soliton generation in the medium. Besides the classical stochastic resonance signature exhibited by each oscillator of the network, our simulation results reveal in particular that the signal-to-noise ratio remains almost constant in the whole network for an appropriate amount of noise. This interesting feature insures for the generated solitons a quality preserved propagation a…
Chaotic Antiferromagnetic Nano-Oscillator driven by Spin-Torque
2021
We theoretically describe the behavior of a terahertz nano-oscillator based on an anisotropic antiferromagnetic dynamical element driven by spin torque. We consider the situation when the polarization of the spin-current is perpendicular to the external magnetic field applied along the anisotropy easy-axis. We determine the domain of the parametric space (field, current) where the oscillator demonstrates chaotic dynamics. Characteristics of the chaotic regimes are analyzed using conventional techniques such as spectra of the Lyapunov exponents. We show that the threshold current of the chaos appearance is particularly low in the vicinity of the spin-flop transition. In this regime, we consi…
Parametric solitons in nonlinear photonic crystals
2007
We present theoretical and experimental investigations on the soliton dynamics associated to multiple second harmonic generation resonances in two-dimensional nonlinear photonic crystals, highlighting a wealth of new possibilities for soliton management in such structures.
Velocity locking of incoherent nonlinear wave packets
2006
We show both theoretically and experimentally in an optical fiber system that a set of incoherent nonlinear waves irreversibly evolves to a specific equilibrium state, in which the individual wave packets propagate with identical group velocities. This intriguing process of velocity locking can be explained in detail by simple thermodynamic arguments based on the kinetic wave theory. Accordingly, the selection of the velocity-locked state is shown to result from the natural tendency of the isolated wave system to approach the state that maximizes the nonequilibrium entropy.
Optical Harmonic Generation Parametric Devices
1999
The sections in this article are 1 Nonlinear Optics: an Actual and Wide Field Of Optics Research 2 Main Applications of Parametric Devices 3 Induced Macroscopic Polarization 4 Electromagnetic Energy Exchange 5 Nonlinear Materials 6 Propagation of the Waves in the Nonlinear Medium 7 Second Harmonic Generation 8 Optical Parametric Generators and Amplifiers 9 Optical Parametric Oscillators 10 Recent Advances in Frequency Conversion
Hot electrons and nonlinear optical nanoantennas
2017
The large field enhancement generated at the surface of a resonant plasmonic nanoparticle, or optical antennas, is the key mechanism that eventually led to the development of nonlinear plasmonics [1-2]. While the resonance may boost the nonlinear yield of an adjacent structure or surrounding medium, it was soon realized that optical antennas possess nonlinear coefficients comparable or exceeding those of standard nonlinear optical materials [3]. We discuss here two nonlinear optical processes — incoherent multi-photon luminescence (MPL) and coherent second-harmonic generation (SHG) — emitted from gold rod optical antennas upon local illumination with a tightly focused femtosecond near-infra…
Effect of a Locally Repulsive Interaction on s-wave Superconductors
2016
The thermodynamic impact of the Coulomb repulsion on s-wave superconductors is analyzed via a rigorous study of equilibrium and ground states of the strong coupling BCS-Hubbard Hamiltonian. We show that the one-site electron repulsion can favor superconductivity at fixed chemical potential by increasing the critical temperature and/or the Cooper pair condensate density. If the one-site repulsion is not too large, a first or a second order superconducting phase transition can appear at low temperatures. The Meißner effect is shown to be rather generic but coexistence of superconducting and ferromagnetic phases is also shown to be feasible, for instance, near half-filling and at strong repul…
Dynamics of surface enrichment: A theory based on the Kawasaki spin-exchange model in the presence of a wall
1991
A mean-field theory is developed for the description of the dynamics of surface enrichment in binary mixtures, where one component is favored by an impenetrable wall. Assuming a direct exchange (Kawasaki-type) model of interdiffusion, a layerwise molecular-field approximation is formulated in the framework of a lattice model. Also the corresponding continuum theory is considered, paying particular attention to the proper derivation of boundary conditions for the differential equation at the hard wall. As an application, we consider the explicit solutions of the derived equations in the case where nonlinear effects can be neglected, studying the approach of an initially flat (homogeneous) co…
Simulation of surface-controlled phase separation in slit pores: Diffusive Ginzburg-Landau kinetics versus Molecular Dynamics
2008
The phase separation kinetics of binary fluids in constrained geometry is a challenge for computer simulation, since nontrivial structure formation occurs extending from the atomic scale up to mesoscopic scales, and a very large range of time needs to be considered. One line of attack to this problem is to try nevertheless standard Molecular Dynamics (MD), another approach is to coarse-grain the model to apply a time-dependent nonlinear Ginzburg–Landau equation that is numerically integrated. For a symmetric binary mixture confined between two parallel walls that prefer one species, both approaches are applied and compared to each other. There occurs a nontrivial interplay between the forma…