Dynamics of vortex-antivortex pairs and rarefaction pulses in liquid light

We present a numerical study of the cubic-quintic nonlinear Schr"odinger equation in two transverse dimensions, relevant for the propagation of light in certain exotic media. A well known feature of the model is the existence of flat-top bright solitons of fixed intensity, whose dynamics resembles the physics of a liquid. They support traveling wave solutions, consisting of rarefaction pulses and vortex-antivortex pairs. In this work, we demonstrate how the vortex-antivortex pairs can be generated in bright soliton collisions displaying destructive interference followed by a snake instability. We then discuss the collisional dynamics of the dark excitations for different initial conditions. We describe a number of distinct phenomena including vortex exchange modes, quasielastic flyby scattering, soliton-like crossing, fully inelastic collisions and rarefaction pulse merging.