Optical vortex-antivortex crystallization in free space

TL;DR

This paper demonstrates that optical vortex-antivortex clusters can form stable lattice patterns in free space, maintained by effective interactions, with potential applications in optical communications and particle manipulation.

Contribution

It introduces a model explaining vortex-antivortex crystallization in free space without nonlinearities, highlighting globally balanced couplings as the stabilizing mechanism.

Findings

VAV clusters can crystallize into stable patterns over several Rayleigh lengths.

The phenomenon occurs without nonlinearities, in free space.

Effective interactions explain the lattice stability.

Abstract

Stable vortex lattices are basic dynamical patterns which have been demonstrated in physical systems including superconductor physics, Bose-Einstein condensates, hydrodynamics and optics. Vortex-antivortex (VAV) ensembles can be produced, self-organizing into the respective polar lattices. However, these structures are in general highly unstable due to the strong VAV attraction. Here, we demonstrate that multiple optical VAV clusters nested in the propagating coherent field can crystallize into patterns which preserve their lattice structures over distance up to several Rayleigh lengths. To explain this phenomenon, we present a model for effective interactions between the vortices and antivortices at different lattice sites. The observed VAV crystallization is a consequence of the globally balanced VAV couplings. As the crystallization does not require the presence of nonlinearities and appears in free space, it may find applications to high-capacity optical communications and multiparticle manipulations. Our findings suggest possibilities for constructing VAV complexes through the orbit-orbit couplings, which differs from the extensively studied spin-orbit couplings.