Collisions between discrete surface spatiotemporal solitons in nonlinear waveguide arrays

We study the effects associated with spatiotemporal light localization near the edge of a semi-infinite array of weakly coupled nonlinear optical waveguides. It was shown earlier that such a system can support the existence of a novel class of $(2+1)$-dimensional continuous-discrete spatiotemporal solitons, which are stable in a broad region of their parameters. We analyze the collisions between this type of spatiotemporal optical solitons and demonstrate that such collisions are strongly affected by the presence of the surface. In particular, since these solitons can be located at different distances from the edge of the waveguide array, we observe a variety of collision scenarios and different outcomes. In addition to well-known scenarios of soliton fusion and symmetric scattering, we get strongly asymmetric outcomes that can be understood as soliton switching.