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

摘要

We embed a pair of vortices with different topological charges in a Gaussianbeam and study its evolution through an astigmatic optical system, a tiltedlens. The propagation dynamics is explained by a closed-form analyticalexpression. Furthermore, we show that a careful examination of the intensitydistribution at a predicted position past the lens can provide us with the netcharge present in the beam. To the best of our knowledge, our method is thefirst non-interferometric technique to measure the net charge of an arbitraryvortex pair. Our theoretical results are well supported by experimentalobservations.