Higher-order Nonlinear Effects Research Articles

Analytical and numerical solutions to the generalized Schrödinger equation with fourth-order dispersion and nonlinearity

This study aims to solve the generalized Schrödinger equation with fourth-order dispersion and cubic-quintic nonlinearity (4-Order-GNLSE) using advanced analytical and numerical methods. The 4-Order-GNLSE is critical in understanding complex wave propagation phenomena in various physical contexts, including optical fibers and fluid dynamics, where higher-order dispersion and nonlinear effects are significant. We employ the Khater II (Khat II) and modified Rational (MRat) methods to construct analytical solutions. To validate these solutions, we utilize the trigonometric-quantic-B-spline (TQBS) method as a numerical scheme, demonstrating a close match between analytical and numerical results. Our findings indicate that the proposed methods effectively capture the intricate dynamics governed by the 4-Order-GNLSE. The results highlight the relevance of these solutions in practical applications, offering new insights into the wave propagation behaviors influenced by higher-order dispersion and nonlinearities. This research provides a significant contribution to the field of nonlinear wave equations, presenting novel solutions and validating methodologies that enhance our understanding and potential applications of these complex systems.

Higher-Order Nonlinear Effects on Optical Soliton Propagation and Their Interactions

Abstract When pursuing femtosecond-scale ultrashort pulse optical communication, one cannot overlook higher-order nonlinear effects. Based on the fundamental theoretical model of the variable coefficient coupled high-order nonlinear Schrödinger equation, we analytically explore the evolution of optical solitons in the presence of high-order nonlinear effects. Moreover, the interactions between two nearby optical solitons and their transmission in a nonuniform fiber are investigated. The stability of optical soliton transmission and interactions are found to be destroyed to varying degrees due to higher-order nonlinear effects. The outcomes may offer some theoretical references for achieving ultra-high energy optical solitons in the future.

Fractional Fokas-Lenells equation: analyzing travelling waves via advanced analytical method

In this paper, we consider the fractional Fokas-Lenells equation, which allows us to analyze how a nonlinear optic pulse spreads in time as single-mode fiber produces higher-order nonlinear effects. We have computed perfectly accurate travelling wave solutions for the Fokas-Lenells equation using the Riccati-Bernoulli sub-Ode approach. For the corresponding equation, we have established three distinct classes of perfectly accurate travelling wave solutions with different free parameters; hyperbolic, trigonometric, and rational. A sophisticated Backlund transformation is implemented to the equation to change it to ordinary differential equation domain, leading to many extra exact solutions.

Elastic overtaking collisions of large-amplitude ion-acoustic solitons

Overtaking collisions of large-amplitude solitons are investigated via fluid simulations for a plasma consisting of cold ions and Boltzmann-distributed electrons. To achieve this, a new fluid simulation code is presented. In addition, a novel approach to construct soliton initial conditions is developed. Using these ideas, initial conditions are combined that allows the simulation of overtaking collisions. It is shown that, in the small-amplitude regime, simulation results agree well with the two-soliton solution obtained from reductive perturbation theory. Interestingly, in the large amplitude regime, both the slow and fast solitons re-emerge after the collision with no significant change, showing that the collisions remain elastic. A comparison between reductive perturbation analysis and the simulations show that the only significant effect of higher order nonlinearities on overtaking collisions is a reduction in the magnitude of the phase shifts of both solitons.

Study of Soliton Interaction in Optical Fibers with Third Order Dispersion and Higher Order Nonlinear Effects

In this paper, we present a numerical approach to solve the GNLSE and analyze soliton interaction phenomena using COMSOL environment. By leveraging the capabilities of COMSOL's PDE module, we can accurately capture the dynamics of solitons and investigate their interactions. We analyze the impact of different parameters such as soliton power, initial separation distance, and dispersion characteristics on the soliton dynamics. Furthermore, we examine the role of higher-order dispersion terms in shaping the soliton interactions. Our findings demonstrate the effectiveness of the proposed numerical approach in accurately simulating and analyzing soliton interaction phenomena. The COMSOL-based methodology provides a flexible and efficient framework for studying complex nonlinear optical systems, enabling researchers to gain insights into the behavior of solitons in different media and design optimized communication systems. This paper contributes to the understanding of soliton dynamics and provides a practical tool for investigating the behavior of solitons in nonlinear dispersive media. The presented numerical approach using COMSOL opens avenues for further research in nonlinear optics and fiber optic communication systems.

Asymptotic analysis of multi-valley dark soliton solutions in defocusing coupled Hirota equations

We construct uniform expressions of such dark soliton solutions encompassing both single-valley and double-valley dark solitons for the defocusing coupled Hirota equation with high-order nonlinear effects utilizing the uniform Darboux transformation, in addition to proposing a sufficient condition for the existence of the above dark soliton solutions. Furthermore, the asymptotic analysis we perform reveals that collisions for single-valley dark solitons typically exhibit elastic behavior; however, collisions for double-valley dark solitons are generally inelastic. In light of this, we further propose a sufficient condition for the elastic collisions of double-valley dark soliton solutions. Our results offer valuable insights into the dynamics of dark soliton solutions in the defocusing coupled Hirota equation and can contribute to the advancement of studies in nonlinear optics.

Optical soliton solution via complete discrimination system approach along with bifurcation and sensitivity analyses for the Gerjikov-Ivanov equation

The aim of this research intends to investigate the complex wave patterns and dynamic behavior of the Gerjikov-Ivanov equation (GIE), commonly known as the derivative nonlinear Schrödinger equation (DNLSE). The GIE model is the one that examines dynamics of optical soliton propagation for transmission technologies, including transcontinental and transoceanic lengths of optical fibers, data transfer, and the telecommunications sector. The GIE equation can be regarded as an extension of the NLSE when certain higher-order nonlinear effects are taken into account. We study various optical soliton solutions, including Jacobian elliptic, hyperbolic, and trigonometric functions, are identified using the polynomial method’s complete discrimination system (CDSPM). In addition, Jacobian elliptic functions can be transformed into solitary wave solutions. We also discuss bifurcation points, sensitivity analysis and critical solution conditions, offering a thorough grasp of the system’s dynamic features. The CDSPM plays an important role in studying equilibrium points, phase diagrams, bifurcation behavior, and performing quantitative and qualitative evaluations.

Tip-enhanced two-photon excited fluorescence spectroscopy of monolayer black phosphorus

The optical properties of monolayer black phosphorus (BP) in two-photon excited fluorescence (TPEF) are pivotal for photoluminescence applications at the single molecular level. In this study, we theoretically examine the TPEF properties of monolayer BP using a tip-enhanced spectroscopy system. We detail the influence of parameters such as the tip radius, the distance between the tip and the BP film, the incidence angle and the tip half-cone angle on the fluorescence excitation and emission enhancement of monolayer BP. This examination employs the finite element method. Our findings reveal that the signal enhancement in TPEF is substantially improved, approximately two orders of magnitude greater than that in single-photon excited fluorescence (SPEF), attributed to the high-order nonlinear coupling effect. By optimising the system configuration, we determined that the TPEF enhancement factor with monolayer BP can reach as high as eight orders of magnitude under an excitation wavelength of 800 nm. The highest spatial resolutions achievable for TPEF and SPEF spectroscopy are also 4.4 nm and 5.3 nm, respectively. These results provide an in-depth understanding of the TPEF enhancement mechanism and are invaluable for designing and applying BP-based optoelectronic devices.

Rational solitons and rogue waves for the integrable nonlocal Lakshmanan-Porsezian-Daniel equation

In this paper, we investigate rational solitons and rogue wave (RW) solutions of the nonlocal Lakshmanan-Porsezian-Daniel (LPD) equation by the generalized Darboux transformation method. The exact rational solutions are presented in terms of determinants whose entries are given by the initial eigenfunction and continuous-wave solution. Their dynamics investigated reveals the interesting patterns such as rational solitons, singular and nonsingular RWs depending on the selection of the free parameters. The compression effects of the RWs with respect to the strength of the higher-order nonlinear effects parameter γ are discussed and graphically illustrated.

Effective Control of Three Soliton Interactions for the High-Order Nonlinear Schrödinger Equation

We take the higher-order nonlinear Schrödinger equation as a mathematical model and employ the bilinear method to analytically study the evolution characteristics of femtosecond solitons in optical fibers under higher-order nonlinear effects and higher-order dispersion effects. The results show that the effects have a significant impact on the amplitude and interaction characteristics of optical solitons. The larger the higher-order nonlinear coefficient, the more intense the interaction between optical solitons, and the more unstable the transmission. At the same time, we discuss the influence of other free parameters on third-order soliton interactions. Effectively regulate the interaction of three optical solitons by controlling relevant parameters. These studies will lay a theoretical foundation for experiments and further practicality of optical soliton communications.

Sonic horizon formation for two-dimensional Bose–Einstein condensates with higher-order nonlinear interaction

Based on the Gross–Pitaevskii equation model that incorporates higher-order nonlinear interaction, we studied sonic black hole and sonic horizon formation involved in nonlinear dynamical evolution for Bose–Einstein condensates with higher-order nonlinear interaction. On the basis of the modified variational method and the scenario where the system starts dynamic evolution from ground state, we derived the typical system distribution width function, which is analytically formulated as periodic oscillation solution and monotonically damped variational oscillation solution under different parametric settings. We also calculated the criteria formula for sonic black hole horizon formation with regard to the two evolution modes: oscillation mode and monotonically decay mode, pictorially demonstrating the time interval of sonic horizon appearance. The theoretical results obtained here can be used to guide relevant experimental studies of sonic horizon and sonic black hole formation for Bose–Einstein condensates incorporating the higher-order nonlinear interaction effects.

Wave-speed management of dipole, bright and W-shaped solitons in optical metamaterials

Wave-speed management of soliton pulses in a nonlinear metamaterial exhibiting a rich variety of physical effects that are important in a wide range of practical applications, is studied both theoretically and numerically. Ultrashort electromagnetic pulse transmission in such inhomogeneous system is described by a generalized nonlinear Schrödinger equation with space-modulated higher-order dispersive and nonlinear effects of different nature. We present the discovery of three types of periodic wave solutions that are composed by the product of Jacobi elliptic functions in the presence of all physical processes. Envelope solitons of the dipole, bright and W-shaped types are also identified, thus illustrating the potentially rich set of localized pulses in the system. We develop an effective similarity transformation method to investigate the soliton dynamics in the presence of the inhomogeneities of media. The application of developed method to control the wave speed of the presented solitons is discussed. The results show that the wave speed of dipole, bright and W-shaped solitons can be effectively controlled through spatial modulation of the metamaterial parameters. In particular, the soliton pulses can be decelerated and accelerated by suitable variations of the distributed dispersion parameters.

Novel optical soliton structures for a defocusing Lakshmanan–Porsezian–Daniel optical system

In this article, under investigation is a defocusing Lakshmanan–Porsezian–Daniel optical (DLPD) system holding higher-order dispersion and higher-order nonlinear effects. Via applying the Darboux transformation method, new analytical solutions are obtained for the system. Some novel intersection solitons and their characteristics are found out under the certain parameter setting. There are four basic soliton structures: (i) bright-dark soliton with reduced amplitude at the intersection point; (ii) bright-dark soliton with increased amplitude at the intersection point; (iii) doubly-bright soliton with bright peaks; (iv) doubly-dark soliton with dark troughs. Furthermore, as the order of the solutions increases, there are more abundant and more complex structures at the intersection point. This indicates that this system can carry out more optical information by exciting higher order solitons.

Impact of higher-order nonlinear saturation effects on modulation instability in three-core oppositely directed coupler with two negative index material channels

Impact of higher-order nonlinear saturation effects on modulation instability in three-core oppositely directed coupler with two negative index material channels

Interplay between spin-orbit couplings and residual interatomic interactions in the modulational instability of two-component Bose-Einstein condensates.

The nonlinear dynamics induced by the modulation instability (MI) of a binary mixture in an atomic Bose-Einstein condensate (BEC) is investigated theoretically under the joint effects of higher-order residual nonlinearities and helicoidal spin-orbit (SO) coupling in a regime of unbalanced chemical potential. The analysis relies on a system of modified coupled Gross-Pitaevskii equationson which the linear stability analysis of plane-wave solutions is performed, from which an expression of the MI gain is obtained. A parametric analysis of regions of instability is carried out, where effects originating from the higher-order interactions and the helicoidal spin-orbit coupling are confronted under different combinations of the signs of the intra- and intercomponent interaction strengths. Direct numerical calculations on the generic model support our analytical predictions and show that the higher-order interspecies interaction and the SO coupling can balance each other suitably for stability to take place. Mainly, it is found that the residual nonlinearity preserves and reinforces the stability of miscible pairs of condensates with SO coupling. Additionally, when a miscible binary mixture of condensates with SO coupling is modulationally unstable, the presence of residual nonlinearity may help soften such instability. Our results finally suggest that MI-induced formation of stable solitons in mixtures of BECs with two-body attraction may be preserved by the residual nonlinearity even though the latter enhances the instability.

Higher-order nonlinear anomalous Hall effects induced by Berry curvature multipoles

In recent years, it has been shown that Berry curvature monopoles and dipoles play essential roles in the anomalous Hall and the nonlinear Hall effects, respectively. In this work, we demonstrate that Berry curvature multipoles (the higher moments of Berry curvatures at the Fermi energy) can induce higher-order nonlinear anomalous Hall (NLAH) effects. Specifically, an AC Hall voltage perpendicular to the current direction emerges, where the frequency is an integer multiple of the frequency of the applied current. Importantly, by analyzing the symmetry properties of all the 3D and 2D magnetic point groups, we note that the quadrupole, hexapole, and even higher Berry curvature moments can cause the leading-order frequency multiplication in certain materials. To provide concrete examples, we point out that the third-order NLAH voltage can be the leading-order Hall response in certain antiferromagnets due to Berry curvature quadrupoles, and the fourth-order NLAH voltage can be the leading response in the surface states of topological insulators induced by Berry curvature hexapoles. Our results are established by symmetry analysis, effective Hamiltonian, and first-principles calculations. Other materials which support the higher-order NLAH effect are further proposed, including 2D antiferromagnets and ferromagnets, Weyl semimetals, and twisted bilayer graphene near the quantum anomalous Hall phase.

Exploration of new solitons in optical medium with higher-order dispersive and nonlinear effects via improved modified extended tanh function method

Throughout this article, the improved modified extended tanh function method is presented for deriving fresh travelling wave alternative solutions in different forms of nonlinear Schrödinger equation (NLSE) with higher-order dispersive and nonlinear effects that describes the propagation of ultra-short optical solitons in an optical fiber medium. For this model, we have a variety of new solutions, including solitons (bright, dark and singular), exponential, singular periodic and Jacobi elliptic solutions. Graphical representations of selected solutions are provided to demonstrate the physical properties of the raised solutions.

Hamiltonian form of extended cubic-quintic nonlinear Schrödinger equation in a nonlinear Klein-Gordon model.

We derive an extended cubic-quintic nonlinear Schrödinger equationwith Hamiltonian structure in a nonlinear Klein-Gordon model with cubic-quintic nonlinearity. We use the nonlinear dispersion relation to properly take into account the input of high-order nonlinear effects in the Hamiltonian perturbation approach to nonlinear modulation. We demonstrate that changing the balance between the cubic and quintic nonlinearities has a significant effect on the stability of unmodulated wave packets to long-wave modulations.

The higher-order nonlinearity and parametric effects on dust-ion-acoustic shock waves

In the case of obliquely propagated small-amplitude shock waves, in this study, we investigate the impacts of higher-order nonlinearity as well as various parameters (such as dust concentrations, viscosity, trapping parameters, etc) on the shock wave structures. The considered magnetized plasma system consists of three components, such as inertial positive ions (mobile), trapped electrons, and immobile negatively charged dust particles. The modified Burgers equation with a dominating dissipative term (in which the viscous effect is significant) is derived initially to examine the lower-order nonlinear and dissipative effects, and then, to the best of our knowledge, the modified Burgers-type linear inhomogeneous equation is derived for the first time to observe the higher-order nonlinear effects on shock waves while the plasma contains trapped electrons. The reductive perturbation method is used for the derivation of the equations, whereas the Abel’s theorem and the method of variation of parameters are used for adding the higher-order effect. From the theoretical investigation, we observe that the higher-order nonlinearity has an increasing effect on the shock amplitude. Furthermore, the viscosity and dust concentration increase the shock width and the phase speed, respectively.

Nth-order smooth positon and breather-positon solutions for the generalized integrable discrete nonlinear Schrödinger equation

In this paper, we investigate the smooth positon and breather-positon solutions of the generalized integrable discrete nonlinear Schrödinger (NLS) equation by the degenerate Darboux transformation (DT). Starting from the zero seed solution, the Nth-order smooth positon solutions are obtained by degenerate DT. The breather solutions including Akhmediev breather, Kuznetsov-Ma breather and space-time periodic breather are derived from the nonzero seed solution. Then the breather-positon solutions are constructed by gradual Taylor series expansion of the eigenfunctions in breather solutions. We study the effect of the coefficient of nonlinear term on these discrete smooth positon solutions and breather-positon solutions, which demonstrates that the interacting region of soliton-positon and breather-positon are highly compressed by higher-order nonlinear effects, but the distance between the two positons has an opposite effect in two waveforms.