Propagation of an arbitrary vortex pair through an astigmatic optical system and determination of its net topological charge

TL;DR

This paper presents a novel non-interferometric method to determine the net topological charge of an arbitrary vortex pair in a Gaussian beam after passing through an astigmatic optical system, supported by theory and experiments.

Contribution

It introduces a new analytical approach and experimental technique for measuring the net topological charge of vortex pairs in optical beams.

Findings

Analytical expression for vortex pair propagation through a tilted lens

First non-interferometric method for net charge measurement

Experimental validation of the theoretical predictions

Abstract

We embed a pair of vortices with different topological charges in a Gaussian beam and study its evolution through an astigmatic optical system, a tilted lens. The propagation dynamics is explained by a closed-form analytical expression. Furthermore, we show that a careful examination of the intensity distribution at a predicted position past the lens can provide us with the net charge present in the beam. To the best of our knowledge, our method is the first non-interferometric technique to measure the net charge of an arbitrary vortex pair. Our theoretical results are well supported by experimental observations.