Short Envelope Solitons. Isotropic and Anisotropic Media

Within the framework of the third-order approximation of the nonlinear wave dispersion theory, we find new classes of short scalar and vector solitons of lengths about several wavelengths. Short scalar solitons are found within the framework of a third-order nonlinear Schrödinger equation (NSE-3) including both the nonlinear dispersion terms and the third-order linear dispersion term. The interaction of such solitons is studied, and the soliton stability is proved. Short vector solitons are found within the framework of a coupled third-order nonlinear Schröodinger equation (CNSE-3). Interaction and stability of such solitons are studied.     

Short Vector Envelope Solitons

We find a class of short vector soliton solutions of the coupled third-order nonlinear Schrödinger equation (CNSE-3) and analyze the stability of such solitons in the adiabatic approximation. The analytical results are confirmed by numerical simulations of the dynamics of perturbed short vector solitons corresponding to the CNSE-3.     

Short Envelope Solitons in Nonconservative Media

We consider the dynamics of short envelope solitons within the framework of the third-order nonlinear Schrödinger equation with allowance for both linear losses and pumping by an external wave field. An equation for the soliton amplitude is derived. The stationary value of the soliton amplitude is found.     

Soliton structures of a wave field with an arbitrary number of oscillations in nonresonance media

A new class of solitary solutions for a wave field is found. This class describes soliton-like structures of a circularly polarized radiation that propagate in a nonresonance medium and which involve an arbitrary number of field oscillations. A feature peculiar to these solutions is that they undergo a smooth transformation from solitons of the Schrödinger type, which correspond to long pulses involving many oscillations, to extremely short visible pulses, which, in fact, do not extend beyond one period. Realizability of such soliton structures is considered for a field of linear polarization, and their structural stability is shown numerically.     

Propagation of optical pulses at an absorption line in the presence of a weak nonlinearity

We examine the propagation of short pulses of light in a resonantly absorbing, weakly nonlinear medium within the limits of a model described by the nonlinear Schrödinger equation. The possibility of transforming pulses of various forms into a soliton signal due to the effects of self-interaction is studied. On the basis of the study of spectra for the associated linear problem, we investigate the break-up of an initial pulse into solitons. We have obtained solutions for two particular cases of the initial pulse.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 36–39, February, 1989.     

Solitons of two-component Bose-Einstein condensates modulated in space and time

In this Letter we present soliton solutions of two coupled nonlinear Schrödinger equations modulated in space and time. The approach allows us to obtain solitons for a large variety of solutions depending on the nonlinearity and potential profiles. As examples we show three cases with soliton solutions: a solution for the case of a potential changing from repulsive to attractive behavior, and the other two solutions corresponding to localized and delocalized nonlinearity terms, respectively.     

Quantum Tomography, Wave Packets, and Solitons

The wave packets, both linear and nonlinear (like solitons) signals described by a complex time-dependent function, are mapped onto positive probability distributions (tomograms). The quasidistributions, wavelets, and tomograms are shown to have an intrinsic connection. The analysis is extended to signals obeying to the von Neumann-like equation. For solitons (nonlinear signals) obeying the nonlinear Schrödinger equation, the tomographic probability representation is introduced. It is shown that in the probability representation the soliton satisfies a nonlinear generalization of the Fokker–Planck equation. Solutions to the Gross–Pitaevskii equation corresponding to solitons in a Bose–Einstein condensate are considered.     

Exact chirped gray soliton solutions of the nonlinear Schrödinger equation with variable coefficients

In this paper, we consider the nonlinear Schrödinger equation with variable coefficients, and by using direct transformation of variables and functions, the explicit chirped gray one- and two-soliton solutions are presented. Based on the exact solutions, we in detail analyze the propagation characteristics of the chirped gray soliton, including the stability against either the deviation from integrable condition or the initial perturbation, and interaction between the chirped gray solitons. The results show that the gray soliton can be compressed by choosing the appropriate initial chirp, and the chirped gray pulses can stably propagate along optical fibers remaining the character of solitons.     

Short optical solitons in fibers

The dynamics of short (of the order of a few wave periods) intense optical pulses and interaction of short optical solitons in fibers are considered within the framework of the third-order nonlinear Schrodinger equation. It is shown that an initial pulse tends to one or a few short solitons plus a linear quasiperiodic wave when the third-order linear dispersion and nonlinear dispersion have parameters of the same sign. The number and parameters of the solitons depend on the magnitudes of initial pulse parameters. Interaction of short optical solitons having different amplitudes is accompanied by radiation of part of the wave field from the area of interaction, by an increase of the soliton with larger amplitude, and a decrease of the soliton with a smaller one. (c) 2000 American Institute of Physics.     

Dynamics and interaction of pulses in the modified Manakov model

The two-component vector nonlinear Schrödinger equation, with mixed signs of the nonlinear coefficients, is considered. This equation is integrable by the inverse scattering transform method. The evolution of a single pulse and interaction of pulses are studied. It is shown that the dynamics of a single pulse is reduced to the scalar nonlinear Schrödinger equation of focusing or defocusing type, depending on the initial parameters. It is found that the interaction of pulses results in the appearance of additional solitons and bound states of several solitons. The asymptotic field profile in the non-soliton regime is also obtained.     

Soliton coupling in birefringent optical fiber with third-order dispersion

Nonlinear coupling of polarized solitons in birefringent optical fiber in the presence of third-order dispersion is considered in the framework of the coupled nonlinear Schrödinger equations. The influence of third-order dispersion on the interaction between solitons is investigated. For sufficiently strong third-order dispersion the interaction may even become repulsive. The stable conditions for solitons of partial pulses are analyzed and amplitude threshold, which decreases with third-order dispersion coefficient decreasing, for the capture of solitons of partial pulses into a coupled two-component pulse is obtained.     

Self-Action of a Supershort Laser Pulse in a Medium with Normal Group-Velocity Dispersion

We present the results of numerical and analytical analysis of solutions of the three-dimensional (3D) nonlinear Schröodinger equation with hyperbolic spatial operator. Evolution of the system is considered in separate for two types of the initial field: a Gaussian distribution and a hollow-type (tubular or horseshoe) distribution. The effect of the nonlinear dispersion on wave-packet splitting during self-compression toward the system axis is studied. It is shown that additional focusing of Gaussian wave packets takes place in a wide range of the nonlinear-dispersion parameter. This effect results in a noticeable amplitude growth of one of the two secondary pulses formed as a result of the splitting. For hollow-type distributions, we note the formation of moving inhomogeneities and the excitation of secondary wave fields typical of the hyperbolic system.     

Generalized Theory of One-Dimensional Steady-State Optical Spatial Solitons

We present a generalized soliton theory based on the one-dimensional generalized nonlinear Schroedinger equation,from which one can easily obtain the bright, dark, and grey soliton waveforms, and their existence curves. We show that the forming conditions of spatial solitons are directly dependent on the relationship between the index perturbation and the intensity, no matter whether the index perturbation is positive or negative. Some relevant examples are presented when the solitons are supported by the photoisomerization nonlinearity.     

One-dimensional EM solitons in ultrashort intense laser pulse-partially stripped plasmas

The one-dimensional electromagnetic (EM) envelope solitons in ultrashort intense laser pulse-partially stripped plasmas were discussed based on the wave equation of intense laser pulse propagating in partially stripped plasmas. Under the weakly relativistic assumption, a modified nonlinear Schrödinger (NLS) equation describing the evolution of the EM field was derived. The analytical analysis shows that in the ultra-short broad beam limits, the relativistic nonlinearity and striction nonlinearity cancel each other, and a one-dimensional laser pulse envelope soliton can be formed only due to the polarization nonlinearity. The relationship between the characteristics of soliton and the parameters of laser pulse and partially stripped plasmas was discussed by numerical analysis.     

Acousto-Optic Solitons in Fibers

It is shown that the deceleration of light pulses down to the velocity of a sound value can be realized in a case of unidirectional parametric interaction of two electromagnetic waves with an acoustic one in the regime of forming three wave acousto-optic solitons. This nonlinear acousto-optic interaction can be realized in long distance systems like fibers. As the result of such an interaction, two types of acousto-optic envelope solitons can propagate in fibers. Modulation of the amplitude of the electromagnetic pump wave can control the soliton velocity.     

Three dimensional stability of solutions of the nonlinear Schrödinger equation

The three dimensional stability of nonlinear wave, soliton, and shock solutions of the nonlinear Schrödinger equation is examined. For the nonlinear waves the analysis is rigorous, whereas solitons are treated as limiting cases of the nonlinear waves. As two different limits yield the same result, this result is included. Shock solutions are again examined as limiting cases of the nonlinear waves, and for them an independent consideration of the limits at plus and minus infinity gives confirmation of the result. In contradistinction to the one dimensional analysis, which gave stability for some of the waves, the soliton and the shock, all these entities are now found to be unstable (though with varying degree of rigour in the treatment).     

Effect of initial pulse shape modulation on spontaneous soliton formation in the NSE model

An initial pulse with fairly steep fronts whose evolution is described by the nonlinear Schrödinger equation, splits into soliton-like pulses (spontaneous soliton formation). The number of solitons formed in this process can be estimated by the number of spectral points of the associated linear Zakharov-Shabat problem for the initial pulse. Exact solutions of the Zakharov-Shabat problem are constructed for some classes of initial piecewise-continuous pulses by using the Darboux method. This allows us to estimate the effect of the shape of the initial pulse on the number of formed solitions and their parameters.V. V. Kuibyshev State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 19–24, June, 1992.     

Analytical soliton solutions for the general nonlinear Schrödinger equation including linear and nonlinear gain (loss) with varying coefficients

An improved homogeneous balance principle and an F-expansion technique are used to construct analytical solutions to the generalized nonlinear Schrödinger equation with distributed coefficients and linear and nonlinear gain (or loss). For limiting parameters, these periodic wave solutions acquire the form of localized spatial solitons. Such solutions exist under certain conditions, and impose constraints on the functions describing dispersion, nonlinearity, and gain (or loss). We present a few characteristic examples of periodic wave and soliton solutions with physical relevance.