Orbital angular momentum and informational entropy in perturbed vortex beams.

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.