Effect of Core Size on Vortex Interactions in Light*

Optical vortices are characterized by a helical wavefront with integer winding, also referred to as
the topological charge, around the center of the vortex. These vortices exhibit dynamic behavior
when implanted in different locations of a Gaussian beam, and it is possible to observe vortex-
vortex interactions as the beam propagates. In the case of an oppositely charged vortex pair
separated symmetrically about the beam axis, the vortices begin with a downward motion in the
transverse plane and then accelerate toward each other. When the beam propagates, these
vortices will at some point annihilate each other, without reemergence on the other side of the
collision. The exact dynamics depend on the shape and size of the core. For smaller cores, the
diffraction of the core has an effect on the dynamics and the annihilation distance is farther along
the propagation axis. I will present our theoretical and experimental results including the impact
of charge and core size on the vortex trajectories. I will also discuss the role of the underlying
phase and amplitude gradients at the location of a given vortex on its motion as the beam
propagates.