Vitality of optical vortices

Abstract

Optical vortices are always created or annihilated in pairs with opposite topological charges. However, the presence of such a vortex dipole does not directly indicate whether they are associated with a creation or an annihilation event. Here we propose a method to distinguish between vortex dipoles that have just been created and those that are about to be annihilated. We use first and second order transverse derivatives of the optical field to construct a quantity that reveals the nature of the dipoles. Numerical examples are provided as demonstration of the method.