Spiral forces established by optical phase singularities

The spiral forces of phase singularities are demonstrated experimentally and numerically by presenting the generation and propagation dynamics of multiple optical vortices embedded in a Gaussian beam. The results reveal that the energy flow established by certain phase singularity will perform the characteristics of force on other singularities whose direction is determined by the sign of the topological charge. The force is confirmed by the fluid-like motions of multi-vortex beams, i.e. singularities undergo rotation (annihilation) with each other when they involve identical (opposite) topological charges. This force mechanism may help develop an intuitive understanding of multi-vortex motion and presents a new viewpoint from which to study the dynamics of singularities.