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We report on the stable self-focusing of light for various degrees of spatial coherence. Since the diffraction of a partially spatial coherent light beam is mainly governed by the transverse correlation width, its self-focusing is generally non-trivial. Here, we systematically demonstrate that partially coherent solitons can be generated in a non-instantaneous nonlinear material when the external parameters are properly adapted to the degree of coherence of the light beam.

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.

Stable dipole-mode vector solitons in photorefractive (PR) crystals are studied, both in numerical simulations and in experimental investigation. Numerically exact multi-humped solitary solutions to the propagation equations of two incoherently coupled beams in PR media with an anisotropic nonlocal material response are found. A continuous set of dipole-mode vector solitons, ranging from the solitons with negligible dipole-mode contribution to the solitons with negligible ground mode contribution, is identified. The results are compared with experimental data.

We study, theoretically and experimentally, multicomponent spatial solitons in nonlinear saturable (isotropic and anisotropic photorefractive) bulk media. We find numerically a family of the three-component dipole-mode solitons and demonstrate their stability in a wide range of the input parameters. We also observe the formation and stability of these spatial solitons in experiment with photorefractive strontium barium niobate (SBN) crystals.

We discuss properties of multicomponent spatial formed by simultaneous co-propagation of few mutually incoherent beams in a slow nonlinear medium. W present experimental results on formation and interaction of these solitons in photorefractive nonlinear crystal.

We predict theoretically a novel type of an extremely robust optical vector soliton that originates from trapping of a dipole (HG/sub 01/-type) mode by a soliton-induced waveguide. As a specific example, we consider two incoherently interacting optical beams propagating along the direction z in a bulk saturable medium. The model describes, in the isotropic approximation, solitons in photorefractive materials.

We report on the first experimental observation of a novel type of optical vector soliton, a {\em dipole-mode soliton}, recently predicted theoretically. We show that these vector solitons can be generated in a photorefractive medium employing two different processes: a phase imprinting, and a symmetry-breaking instability of a vortex-mode vector soliton. The experimental results display remarkable agreement with the theory, and confirm the robust nature of these radially asymmetric two-component solitary waves., 4 pages, 8 figures; pictures in the PRL version are better quality

We study the mutual trapping of two dipole-mode light beams in a medium with a nonlocal anisotropic saturable nonlinearity. It is shown that the incoherent attraction of perpendicularly aligned dipole-mode beams leads to the stabilization of their composite structure. Our numerical analysis gives a stationary solution that is stable only with respect to small amplitude modulations. The coupled solitary structure disintegrates in a well-defined way when the numerical perturbations or the experimental propagation length exceeds a certain limit. In this case a new and more robust, multicomponent solitary transverse light structure consisting of two dipole-mode vector solitons will be generated.

We study, both theoretically and experimentally, the scattering properties of optical dipole-mode vector solitons - radially asymmetric composite self-trapped optical beams. First, we analyze the soliton collisions in an isotropic two-component model with a saturable nonlinearity and demonstrate that in many cases the scattering dynamics of the dipole-mode solitons allows us to classify them as ``molecules of light'' - extremely robust spatially localized objects which survive a wide range of interactions and display many properties of composite states with a rotational degree of freedom. Next, we study the composite solitons in an anisotropic nonlinear model that describes photorefractive nonlinearities, and also present a number of experimental verifications of our analysis., Comment: 8 pages + 4 pages of figures

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.