Beam steering and topological transformations driven by interactions between a discrete vortex soliton and a discrete fundamental soliton

We study coherent and incoherent interactions between a discrete vortex soliton and a discrete fundamental soliton in two-dimensional photonic lattices, which present a scheme for all-optical routings and topological transformations of vorticities. Due to the multilobe intensity and π/2-phase delay between each two lobes of the discrete vortex soliton, the coherent soliton interactions allow both solitons to evolve into localized states with a single lobe on multiple different possible destination ports, which depend on the initial phase of the discrete fundamental soliton. We show that charge flippings of phase singularities and orbital angular momentum transfer can occur during the coherent interactions between the two solitons. For incoherent interactions, by controlling the relative powers of the two solitons, we reveal that soliton steering can be realized by either attracting the discrete fundamental soliton to four ports or localizing the four-lobe discrete vortex soliton into a ring soliton.