Search results for "Linear"
showing 10 items of 7165 documents
Solitons and modulational instability
1996
We introduce the localized nonlinear waves called solitons which can occur in nature with different profiles such as kink, pulse, and envelope solitons. The envelope-soliton is important because without modulation the wave carry no information. It is a solution of the so-called nonlinear Schrodinger equation which describes the evolution of dispersive and weakly nonlinear waves. The generation of envelope soliton trains can result from the modulational instability phenomenon that leads to self induced modulations, with respect to small perturbations, such as noise, of input plane wave.
Nonlinear Schrödinger models and modulational instability in real electrical lattices
1995
International audience; In nonlinear dispersive media, the propagation of modulated waves, such as envelope (bright) solitons or hole (dark) solitons, has been the subject of considerable interest for many years, as for example in nonlinear optics [A.C. Newell and J.V. Moloney, Nonlinear Optics (Addison-Presley, 1991)]. On the other hand, discrete electrical transmission lines are very convenient tools to study the wave propagation in 1D nonlinear dispersive media [A.C. Scott (Wiley-Interscience, 1970)]. In the present paper, we study the generation of nonlinear modulated waves in real electrical lattices. In the continuum limit, our theoretical analysis based on the Nonlinear Schrodinger e…
Classical and Quantum Nonultralocal Systems on the Lattice
1997
We classify nonultralocal Poisson brackets for 1-dimensional lattice systems and describe the corresponding regularizations of the Poisson bracket relations for the monodromy matrix. A nonultralocal quantum algebras on the lattices for these systems are constructed. For some class of such algebras an ultralocalization procedure is proposed. The technique of the modified Bethe-Anzatz for these algebras is developed and is applied to the nonlinear sigma model problem.
Polarization of the Radiation Emitted in GaAs Semiconductors Driven by Far Infrared Fields
2010
The effects due to the mixing of two far infrared electric fields on the harmonic generation process in low doped GaAs bulks are studied by a three dimensional multivalleys Monte Carlo simulation. The conversion efficiency is calculated by using the appropriate Maxwell equation for the propagation of an electro-magnetic wave along a given direction in the medium. In particular, we focus our attention on the polarization of the generated harmonics, by comparing the polarization obtained from the mixing of an oscillating field with a static electric field with that obtained in the presence of two cyclostationary fields, having an integer ratio between the two frequencies. The findings show th…
Polarization of high harmonic generated spectra in H+2ion
2013
AbstractWe study the polarization of the harmonics generated by a homonuclear diatomic molecule in the presence of an intense, linearly polarized laser field. The polarization parameters of the emitted radiation are investigated as a function of the angle between the laser electric field and the molecular axis. The calculations are carried out by assuming a single active electron model with fixed nuclei; a two-dimensional model of the system is used. We find a different dependence of the parameters of the harmonics vs in the first or second half of the emitted spectrum. In particular, the differences are accentuated for , while for higher angles, until the perpendicular orientation, almost …
Polarization phenomena in a laser coherently pumped by a linearly polarized field
1998
The field intensity and polarization behaviour of an optically pumped laser is investigated in different operating conditions. For a linearly polarized pump field, a strong gain anisotropy is induced which favours generation of light with a polarization parallel to that of the pump field. Thus gain anisotropy can be counterbalanced by cavity-loss anisotropy only at low pumping field intensities, and the interplay between both types of anisotropy leads to polarization switching phenomena. In contrast to the case of the incoherently pumped laser, the decay rate for the magnetic dipole induced on the J = 1 level plays a minor role in determining the polarization dynamics. The influence of a lo…
Polarization Domain Wall Solitons with Counterpropagating Laser Beams
1998
The coupling between two intense laser beams in a nonlinear dielectric leads to a host of physical effects. In particular, the interaction between the polarization states of two counterpropagating ligth beams may generate polarization domain wall (PDW7) solitons [1]. We present what we believe is the first experimental observation of PDW7 soliton formation in a nonlinear dielectric medium.
Reduction of focus size in tightly focused linearly polarized beams
2004
The electromagnetic theory predicts that when a linearly polarized collimated field is focused by a high-angle focusing system, components perpendicular to the initial polarization are generated. The use of annular masks to reduce the area of the focal spot usually increases the magnitude of this phenomenon, known as depolarization. We present a class of masks, the three-ring masks, which are important because they narrow the central lobe of the focal intensity distribution without increasing the depolarization. This can be very useful in modern optical applications, such as confocal microscopy or multiphoton scanning microscopy.
On the application of canonical perturbation theory to floppy molecules
2000
International audience; Canonical perturbation theory (CPT) is a powerful tool in the field of molecular physics. It consists of a series of coordinate transformations aimed at rewriting the Hamiltonian in a simpler form without modifying the geometry of the phase space. The major achievement of CPT is the straightforward derivation of relations between the physically meaningful parameters of potential energy surfaces and the coefficients of the so-called effective Hamiltonians. While most of the studies performed up to date deal with surfaces expanded in polynomial series around a single minimum, CPT has also been applied to mixed polynomial/trigonometric expansions in the treatment of tor…
Noise delayed decay of unstable states: theory versus numerical simulations
2004
We study the noise delayed decay of unstable nonequilibrium states in nonlinear dynamical systems within the framework of the overdamped Brownian motion model. We give the exact expressions for the decay times of unstable states for polynomial potential profiles and obtain nonmonotonic behavior of the decay times as a function of the noise intensity for the unstable nonequilibrium states. The analytical results are compared with numerical simulations.