Multipole composite spatial solitons: Theory and experiment

We discuss the properties of composite (or vector) spatial optical solitons created by the incoherent interaction of two optical beams and associated with higher-order modes guided by a soliton-induced waveguide in a bulk medium. Such stationary (2 + 1)-dimensional self-trapped localized structures include, in particular, vortex-and dipole-mode vector solitons and also incorporate higher-order multipole spatial solitons in a bulk medium, such as quadrupole solitons and necklace-type composite beams. We overview our theoretical and experimental results for the structure, formation, and stability of these self-trapped composite optical beams and also discuss the effects of anisotropy and of the nonlocality of the photorefractive nonlinearity on their properties. Additionally, we demonstrate, analytically and experimentally, that an array of the dipole-mode vector solitons can be generated as a result of the transverse instability of a quasi-one-dimensional two-hump soliton stripe in a saturable nonlinear optical medium.