Multicomponent Solitons Research Articles

Incoherent multi-gap optical solitons in nonlinear photonic lattices

We demonstrate numerically that partially incoherent light can be trapped in the spectral band gaps of a photonic lattice, creating partially incoherent multi-component spatial optical solitons in a self-defocusing nonlinear periodic medium. We find numerically such incoherent multi-gap optical solitons and discuss how to generate them in experiment by interfering incoherent light beams at the input of a nonlinear periodic medium.

Multiport soliton devices with controllable transmission

We describe new planar multiport devices written by spatial solitons that are composed of several nonlinearly coupled components in Kerr-type media. Such devices have no radiation losses at a given wavelength. We demonstrate that, for the same relative angle between the input soliton-induced channels, one can vary the transmission coefficients into the output channels by adjusting the polarizations of multicomponent solitons. We determine analytically the transmission properties and discuss two types of experimental embodiment of the proposed device.

Interaction of vector solitons with a nonlinear interface

We develop the analytical method of field momenta for analyzing the dynamics of optical vector solitons in photorefractive nonlinear media. First, we derive the effective evolution equations for the parameters of multi-component solitons composed of incoherently coupled beams and investigate the soliton internal oscillations associated with the relative motion of the soliton components. Then, we apply this method for analyzing the vector soliton scattering by a nonlinear interface. In particular, we show that a vector soliton can be reflected, transmitted, captured, or split into separate components, depending on the initial energy of its internal degree of freedom. The results are verified by direct numerical simulations of spatial optical solitons in photorefractive nonlinear media.

Spatial optical (2+1)-dimensional scalar- and vector-solitons in saturable nonlinear media

(2+1)-dimensional optical spatial solitons have become a major field of research in nonlinear physics throughout the last decade due to their potential in adaptive optical communication technologies. With the help of photorefractive crystals that supply the required type of nonlinearity for soliton generation, we are able to demonstrate experimentally the formation, the dynamic properties, and especially the interaction of solitary waves, which were so far only known from general soliton theory. Among the complex interaction scenarios of scalar solitons, we reveal a distinct behavior denoted as anomalous interaction, which is unique in soliton-supporting systems. Further on, we realize highly parallel, light-induced waveguide configurations based on photorefractive screening solitons that give rise to technical applications towards waveguide couplers and dividers as well as all-optical information processing devices where light is controlled by light itself. Finally, we demonstrate the generation, stability and propagation dynamics of multi-component or vector solitons, multipole transverse optical structures bearing a complex geometry. In analogy to the particle-light dualism of scalar solitons, various types of vector solitons can - in a broader sense - be interpreted as molecules of light.

Multi-component vector solitons in photorefractive crystals

We study the existence and stability of multi-component spatial optical solitons in anisotropic nonlocal photorefractive media. For the case of three components, we find numerically the whole family of composite solitons with two perpendicular dipole components, and show their stability for a wide range of parameters. We confirm our theoretical results by an experimental observation of these novel types of composite optical solitons in a photorefractive strontium barium niobate crystal.

Multicomponent dipole-mode spatial solitons

We study (2+1) -dimensional multicomponent spatial vector solitons with a nontrivial topological structure of their constituents and demonstrate that these solitary waves exhibit a symmetry-breaking instability, provided their total topological charge is nonzero. We describe a novel type of stable multicomponent dipole-mode solitons with intriguing swinging dynamics.

Incoherently coupled steady-state soliton pairs in biased photorefractive-photovoltaic materials.

A theory on incoherently coupled soliton pairs for photorefractive screening solitons is developed that gives rise to incoherently coupled steady-state soliton pairs and multicomponent spatial solitons in biased photorefractive-photovoltaic materials, which result from both the bulk photovoltaic effect and the spatially nonuniform screening of the external bias field. When the bulk photovoltaic effect is neglectable, these soliton pairs are the previously studied soliton pairs for screening solitons, these multicomponent spatial solitons predict incoherently coupled multicomponent spatial solitons for screening solitons, and their space-charge field is the space-charge field of screening solitons. When the external field is absent, these soliton pairs and multicomponent spatial solitons predict incoherently coupled soliton pairs and multicomponent spatial solitons for photovoltaic solitons, and their space-charge field is the space-charge field of photovoltaic solitons. The stability of these soliton pairs and multicomponent spatial solitons is also discussed using the modulation instability theory.

Domain wall solitons in binary mixtures of Bose-Einstein condensates.

The structure and dynamics of the domain walls separating segregated condensates in trapped mixtures of repulsive Bose-Einstein condensates are studied. Our work reveals that, under fairly general conditions, these domain walls behave as independent dynamical entities, which allows us to identify them as constituting a novel class of multicomponent solitons in Bose-Einstein condensates.

Composite spatial solitons in a saturable nonlinear bulk medium

We review the generation of the recently predicted multi-component spatial optical solitons in a saturable nonlinear bulk medium. We present numerical simulations for an effectively isotropic model and experimental results for a set of different combinations of a Gaussian beam co-propagating incoherently with a beam of a more complex internal structure, such as a higher order transverse laser mode. We discuss the different formation processes and the general properties of a variety of different dipole-mode composite solitons and expand our investigations to the generation of a quadrupole-mode composite soliton.

Higher order nonlinear optical effects on polarized dark solitons

We extend our previous work on the construction of multi-component dark-type solitons of the vector nonlinear Schrödinger equation to include higher-order nonlinear optical effects. Exact solutions, such as the dark–dark, the bright–dark and the bright–bright pair of solitons are found explicitly and the effects of higher-order nonlinear terms are explained.

Systematic construction of multicomponent optical solitons

A systematic method is presented to construct multicomponent optical solitons for the system governed by the vector nonlinear Schr\"odinger equation. By solving the characteristic eigenvalue problem, we obtain a general n-component soliton solution in the presence of nonzero background fields. In the two-component case, we show that this general solution not only includes previously known soliton solutions, e.g., bright-bright, dark-bright, dark-dark pair solitons for self-focusing or self-defocusing media, but depending on the choice of parameters it also exhibits different types of soliton solution. In particular, we obtain a general dark-bright type solution in a self-focusing medium, which describes a breakup of a dark-bright pair into another dark-bright pair and an ``oscillating'' soliton, or the reverse fusing process. In the case of a self-defocusing medium, we generalize the previously known static dark-dark pair and show that a general dark-dark pair is non-static and oscillates periodically through exchanging energies between two components. It is shown that the static case arises when the complex soliton parameter is restricted to a pure imaginary number. We address about the criterion for testing singularity in a general solution in terms of solution parameters, and also about the non-Abelian $\mathrm{SU}(n)$ symmetry of the system.

Multicomponent two-dimensional solitons carrying topological charges

We propose multihump N-component two-dimensional vector solitons for which each constituent carries a different topological charge. These new structures exhibit a unique triple-point phase diagram that is completely absent in the two-component limit.

Multicomponent 'dark' cnoidal waves: stability and soliton asymptotes

The problem of steady-state propagation of several mutually incoherent optical waves — components of 'dark' multicomponent solitons and cnoidal waves — through a photorefractive crystal with a drift nonlinearity of the defocusing type is considered and solved. Analytical expressions are obtained for the distributions of the optical field between the components of the resulting solutions, containing up to three self-consistent components inclusive. It is shown that these solutions are stable and that their spatial structure is retained in mutual collisions and after stochastic perturbations of the intensity distributions.

Cross-modulation coupling of incoherent soliton modes in photorefractive crystals

A problem of nonlinear wave propagation through a photorefractive crystal (PRC) with drift nonlinearity has been evaluated. A class of spatially localized solitonlike solutions with finite energy has been found. Solutions of this class can be considered as multicomponent solitons, combined by two or more mutually incoherent self-consistent components bonded by cross-modulation coupling. Light field spatial distributions of the components look like zero and higher order modes of their common waveguide formed in PRC due to its nonlinearity. We have shown such a soliton is stable on distances of several diffraction lengths and its spatial structure is robust to collisions and appreciable (more than 10% in intensity) stochastic perturbations of the intensity distributions. With taking into account saturation of PRC nonlinearity, parameters of all the soliton components (their amplitudes and widths) change quasiperiodically as the soliton propagates. The components do not exchange energy while a small fraction of the energy is emitted on few diffraction lengths. We discuss also a possibility of excitation of incoherent solitonlike multielectron states in conjugated polymers, ferromagnetics, and superconductors. These states could correspond to some mutually incoherent and self-consistent wave packets composed of electronic wave functions and propagating along conjugated chains or prominent atomic planes.

Forming stable nonlinear lightguides with cross-modulation self-locking of incoherent soliton modes

This paper discusses a new class of spatially localized soliton solutions with bounded energy in the problem of the nonlinear propagation of a light beam along a photorefractive crystal (PRC) with a drift mechanism of nonlinear response. Solitons of this class correspond to stable propagation in the PRC of two or more wave packets (components) that are matched in intensity distribution but incoherent. Their spatial distributions correspond to simultaneous cross-modulation self-locking of its first-and higher-order modes into the common nonlinear waveguide formed by them. It is shown that such multicomponent solitons can be implemented and that they are structurally stable both with respect to collisions and with respect to substantial (more than 10% in intensity) stochastic perturbations of their components as they propagate to distances of the order of several diffraction lengths. The paper discusses the possibility that conjugate polymers, antiferromagnets, and superconductors can contain unusual states corresponding to the stable propagation of two or more mutually incoherent but matched electron wave packets along conjugate chains or along isolated atomic planes.