Orbital angular momentum and informational entropy in perturbed vortex beams

TL;DR

This study explores how sector perturbations affect vortex beams, revealing that small perturbations leave orbital angular momentum unchanged while increasing entropy, and large perturbations significantly reduce OAM and raise entropy due to vortex formation.

Contribution

The paper provides both theoretical and experimental insights into how sector perturbations influence vortex beam properties, especially OAM and informational entropy.

Findings

Small sector perturbations do not significantly affect OAM.

Entropy increases rapidly with perturbation size due to vortex creation.

Large perturbations reduce OAM to near zero and sharply increase entropy.

Abstract

We theoretically and experimentally investigated transformations of vortex beams subjected to sector perturbations in the form of hard-edged aperture. The transformations of the vortex spectra, the orbital angular momentum, and the informational entropy of the perturbed beam were studied. We found that relatively small angular sector perturbations have almost no effect on OAM, although the informational entropy is rapidly increasing due to the birth of new optical vortices caused by diffraction by diaphragm edges. At large perturbation angles, the uncertainty principle between the angle and OAM involves vortices, with both positive and negative topological charges, so that the OAM decreases to almost zero, and the entropy increases sharply.