Stable Higher-Charged Vortex Solitons in Optically-Induced Lattices

Vortices are fundamental objects which appear in many branches of physics [1] such as optics [2, 3] and Bose-Einstein condensates [4]. In nonlinear optics, vortex solitons are associated with the phase dislocations (or phase singularities) carried by the nondiffracting optical beams [5], and share many common properties with the vortices observed in other systems, e.g., superfluids and Bose-Einstein condensates [6, 7]. In a homogeneous medium, stable vortex solitons were proposed to exist in the so-called cubic-quintic or other similar nonlinear media, for example, combination of χ(2) and χ(3) nonlinear media, based on competing self-focusing and self-defocusing nonlinearities [8–11]. However, the experimental realization of vortex solitons in such media is hard, as the requirement of very high energy flow of light usually excites other higher-order nonlinearities, which may be dominant and suppress the occurrence of competing nonlinearities.