Evolution of the phase singularities in edge-diffracted optical-vortex beams

TL;DR

This paper investigates how optical-vortex cores move within a beam when an edge diffracts it, revealing spiral trajectories and sudden jumps linked to topological vortex reactions, through theoretical analysis and experiments.

Contribution

It provides new insights into the dynamics of optical vortices during edge diffraction, including the mechanisms behind vortex jumps and topological reactions.

Findings

Optical-vortex cores follow spiral trajectories during edge diffraction.

Vortex jumps are associated with topological birth and annihilation events.

Experimental and theoretical results agree on vortex dynamics mechanisms.

Abstract

We study, both theoretically and by experiment, migration of the amplitude zeros within a fixed cross section of the edge-diffracted optical-vortex beam, when the screen edge performs permanent translation in the transverse plane from the beam periphery towards the axis. Generally, the amplitude zeros (optical-vortex cores) describe spiral-like trajectories. When the screen edge advances uniformly, the motion of the amplitude zeros is not smooth and sometimes shows anomalously high rates, which make an impression of instantaneous "jumps" from one position to another. We analyze the nature, conditions and mechanism of these jumps and show that they are associated with the "birth - annihilation" topological reactions involving the optical vortex dipoles.