Optical solitons with non-Kerr law nonlinearity and inter-modal dispersion with time-dependent coefficients

This paper studies optical solitons with non-Kerr law nonlinearity, in the presence of inter-modal dispersion. The coefficients of group velocity dispersion, nonlinearity and inter-modal dispersion terms have time-dependent coefficients. The types of nonlinearity that are considered are Kerr, power, parabolic and dual-power laws. The solitary wave ansatz is used to carry out the integration of the governing nonlinear Schrödinger’s equation with time-dependent coefficients. Both, bright and dark optical solitons, are considered, in this paper. Finally, numerical simulations are also given in each of these cases. The only necessary condition for these solitons to exist is that these time-dependent coefficients of group velocity dispersion and inter-modal dispersion are Riemann integrable.     

Dynamics of topological optical solitons with time-dependent dispersion,nonlinearity and attenuation

In this paper, the dark or topological optical 1-soliton solution of the nonlinear Schrödinger’s equation is obtained. The time-dependent coefficients of the group velocity dispersion, Kerr nonlinearity and the attenuation terms are considered. This leads to the constraint relation between these coefficients for the topological solitons to exist. All what is necessary is that these time-dependent coefficients be simply Riemann integrable.     

1-Soliton solution of the complex KdV equation in plasmas with power law nonlinearity and time-dependent coefficients

In this paper, the complex Korteweg-de Vries equation with power law nonlinearity is studied in presence of perturbation terms. The exact 1-soliton solution is obtained. It will be seen that the time-dependent coefficients must be simply Riemann integrable for the solitons to exist. The solitary wave ansatz is used to carry out the integration.     

Topological 1-soliton solution of Kadomtsev-Petviashvili equation with power law nonlinearity

This paper studies the Kadomtsev-Petviasvili equation with power law nonlinearity. Topological 1-soliton solution is obtained and the parameter domain is identified for these solitons to exist. The solitary wave ansatz is used to obtain this solution.     

Optical soliton perturbation with time-dependent coefficients in a log law media

This paper obtains the exact 1-soliton solution to the nonlinear Schrödinger’s equation with log law nonlinearity in presence of time-dependent perturbations. The dispersion and nonlinearity are also taken to be time-dependent. The perturbation terms that are considered are linear attenuation and inter-modal dispersion. The constraint condition between the time-dependent coefficients also fall out as a necessary condition for the solitons to exist.     

Topological 1-soliton solution of the Biswas–Milovic equation with power law nonlinearity

This paper studies the topological or dark solitons due to the Biswas–Milovic equation with power law nonlinearity. The coefficients of the dispersion and nonlinearity terms are time dependent. The damping (gain) term with time-dependent coefficient is also taken into consideration. The solitary wave ansatz is used to carry out the integration. The only requirement is that the coefficient of the damping term is Riemann integrable.     

Chaotic motions for a perturbed nonlinear Schrödinger equation with the power-law nonlinearity in a nano optical fiber

Perturbed nonlinear Schrödinger (NLS) equation with the power-law nonlinearity in a nano optical fiber is studied with the help of its equivalent two-dimensional planar dynamic system and Hamiltonian. Via the bifurcation theory and qualitative theory, equilibrium points for the two-dimensional planar dynamic system are obtained. With the external perturbation taken into consideration, chaotic motions for the perturbed NLS equation with the power-law nonlinearity are derived based on the equilibrium points.     

General N‐Dark–Dark Solitons in the Coupled Nonlinear Schrödinger Equations

N‐dark–dark solitons in the integrable coupled NLS equations are derived by the KP‐hierarchy reduction method. These solitons exist when nonlinearities are all defocusing, or both focusing and defocusing nonlinearities are mixed. When these solitons collide with each other, energies in both components of the solitons completely transmit through. This behavior contrasts collisions of bright–bright solitons in similar systems, where polarization rotation and soliton reflection can take place. It is also shown that in the mixed‐nonlinearity case, two dark–dark solitons can form a stationary bound state.     

Stability of peakons for the Novikov equation

In this paper we study the orbital stability of the peaked solitons to the Novikov equation, which is an integrable Camassa–Holm type equation with cubic nonlinearity. We show that the shapes of these peaked solitons are stable under small perturbations in the energy space.     

Topological exact soliton solution of the power law KdV equation

This paper obtains the exact 1-soliton solution of the perturbed Korteweg-de Vries equation with power law nonlinearity. The topological soliton solutions are obtained. The solitary wave ansatz is used to carry out this integration. The domain restrictions are identified in the process and the parameter constraints are also obtained. It has been proved that topological solitons exist only when the KdV equation with power law nonlinearity reduces to simply KdV equation.     

Spatial Vector Solitons in Nonlinear Photonic Crystal Fibers

We study spatial vector solitons in a photonic crystal fiber (PCF) made of a material with the focusing Kerr nonlinearity. We show that such two-component localized nonlinear waves consist of two mutually trapped components confined by the PCF linear and the self-induced nonlinear refractive indices, and they bifurcate from the corresponding scalar solitons. We demonstrate that, in a sharp contrast with an entirely homogeneous nonlinear Kerr medium where both scalar and vector spatial solitons are unstable and may collapse, the periodic structure of PCF can stabilize the otherwise unstable two-dimensional spatial optical solitons. We apply the matrix criterion for stability of these two-parameter solitons, and verify it by direct numerical simulations.     

Solutions of Kadomtsev–Petviashvili equation with power law nonlinearity in 1+3 dimensions

This paper studies the solution of the Kadomtsev–Petviasvili equation with power law nonlinearity in 1+3 dimensions. The Lie symmetry approach as well as the extended tanh‐function and G′/G methods are used to carry out the analysis. Subsequently, the soliton solution is obtained for this equation with power law nonlinearity. Both topological as well as non‐topological solitons are obtained for this equation. Copyright © 2010 John Wiley & Sons, Ltd.     

Bistable Solitons in Single- and Multichannel Waveguides with the Cubic-Quintic Nonlinearity

We consider spatial solitons in a channel waveguide or in a periodic array of rectangular potential wells (the Kronig-Penney (KP) model) in the presence of the uniform cubic-quintic (CQ) nonlinearity. Using the variational approximation and numerical methods, we. nd two branches of fundamental (single-humped) soliton solutions. The soliton characteristics, in the form of the integral power Q (or width w) vs. the propagation constant k, reveal a strong bistability with two different solutions found for a given k. Violating the known Vakhitov-Kolokolov criterion, the solution branches with dQ/dk > 0 and dQ/dk < 0 are simultaneously stable. Various families of higher-order solitons are also found in the KP version of the model: symmetric and antisymmetric double-humped solitons, three-peak solitons with and without the phase shift π between the peaks, etc. In a relatively shallow KP lattice, all the solitons belong to the semi-infinite gap beneath the linear band structure of the KP potential, while finite gaps between the bands remain empty (solitons in the finite gaps can be found if the lattice is much deeper). But in contrast to the situation known for the model combining a periodic potential and the self-focusing Kerr nonlinearity, the fundamental solitons fill only a finite zone near the top of the semi-infinite gap, which is a manifestation of the saturable character of the CQ nonlinearity. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 144, No. 2, pp. 324–335, August, 2005. An erratum to this article is available at .     

Topological 1-soliton solution of the nonlinear Schrodinger’s equation with Kerr law nonlinearity in 1 + 2 dimensions

In this paper, the topological 1-soliton solution of the nonlinear Schrödinger’s equation in 1 + 2 dimensions is obtained by the solitary wave ansatze method. These topological solitons are studied in the context of dark optical solitons. The type of nonlinearity that is considered is Kerr type.     

A numerical method for calculating solitons of the nonlinear Schödinger equation in the axially symmetric case

A numerical method is proposed for determination of the eigenfunctions and eigenvalues of the nonlinear Schrödinger equation in the axially symmetric case. Optical solitons interpreted in the physical sense are found for various values of the nonlinearity coefficient by means of the developed method. As has previously been shown by other authors, such solitons are unstable under small perturbations of their shape. Since the considered problem finds numerous applications, methods providing for soliton stabilization are widely discussed in the literature. One of these methods involves strong modulation of the medium nonlinearity or even the reversal of the nonlinearity sign, which necessitates taking into account the wave reflected from irregularities and analyzing additionally the applicability of the mathematical model. We show that, theoretically, it is possible to stabilize a soliton via weak modulation of the cubic-nonlinearity coefficient. Such modulation ensures alternation of the length of nonlinear layers and enables one to increase the path length by a factor of 70 without a beam collapse.     

Dynamics of solitons in plasmas for the complex KdV equation with power law nonlinearity

This paper obtains the 1-soliton solution of the complex KdV equation with power law nonlinearity. The solitary wave ansatz is used to carry out the integration. The soliton perturbation theory for this equation is developed and the soliton cooling is observed for bright solitons. Finally, the dark soliton solution is also obtained for this equation.     

On the optimal focusing of solitons and breathers in long‐wave models

Conditions of optimal (synchronized) collisions of any number of solitons and breathers are studied within the framework of the Gardner equation (GE) with positive cubic nonlinearity, which in the limits of small and large amplitudes tends to other long‐wave models, the classic and the modified Korteweg–de Vries equations. The local solution for an isolated soliton or breather within the GE is obtained. The wave amplitude in the focal point is calculated exactly. It exhibits a linear superposition of partial amplitudes of the solitons and breathers. The crucial role of the choice of proper soliton polarities and breather phases on the cumulative wave amplitude in the focal point is demonstrated. Solitons are most synchronized when they have alternating polarities. The straightforward link to the problem of synchronization of envelope solitons and breathers in the focusing nonlinear Schrödinger equation is discussed (then breathers correspond to envelope solitons propagating above a condensate).     

Soliton perturbation theory for the fifth order KdV-type equations with power law nonlinearity

The adiabatic parameter dynamics of solitons, due to fifth order KdV-type equations with power law nonlinearity, is obtained with the aid of soliton perturbation theory. In addition, the small change in the velocity of the soliton, in the presence of perturbation terms, is also determined in this work.     

Darboux transformation and soliton solutions for the coupled cubic-quintic nonlinear Schrödinger equations in nonlinear optics

In this paper, by virtue of the Darboux transformation (DT) and symbolic computation, the quintic generalization of the coupled cubic nonlinear Schrödinger equations from twin-core nonlinear optical fibers and waveguides are studied, which describe the effects of quintic nonlinearity on the ultrashort optical pulse propagation in non-Kerr media. Lax pair of the equations is obtained and the corresponding DT is constructed. Moreover, one-, two- and three-soliton solutions are presented in the forms of modulus. Features of solitons are graphically discussed: (1) head-on and overtaking elastic collisions of the two solitons; (2) periodic attraction and repulsion of the bounded states of two solitons; (3) energy-exchanging collisions of the three solitons.     

The virial theorem and ground state energy estimates of nonlinear Schrödinger equations in $$\mathbb {R}^2$$ with square root and saturable nonlinearities in nonlinear optics

The virial theorem is a nice property for the linear Schrödinger equation in atomic and molecular physics as it gives an elegant ratio between the kinetic and potential energies and is useful in assessing the quality of numerically computed eigenvalues. If the governing equation is a nonlinear Schrödinger equation with power-law nonlinearity, then a similar ratio can be obtained but there seems to be no way of getting any eigenvalue estimates. It is surprising as far as we are concerned that when the nonlinearity is either square-root or saturable nonlinearity (not a power-law), one can develop a virial theorem and eigenvalue estimates of nonlinear Schrödinger (NLS) equations in \({{\mathbb {R}}^{2}}\) with square-root and saturable nonlinearity, respectively. Furthermore, we show here that the eigenvalue estimates can be used to obtain the 2nd order term (which is of order \(\ln \Gamma \)) of the lower bound of the ground state energy as the coefficient \(\Gamma \) of the nonlinear term tends to infinity.