title: Topological features of vector vortex beams perturbed with uniformly polarized light.
abstract: Optical singularities manifesting at the center of vector vortex beams are unstable, since their topological charge is higher than the lowest value permitted by Maxwell's equations. Inspired by conceptually similar phenomena occurring in the polarization pattern characterizing the skylight, we show how perturbations that break the symmetry of radially symmetric vector beams lead to the formation of a pair of fundamental and stable singularities, i.e. points of circular polarization. We prepare a superposition of a radial (or azimuthal) vector beam and a uniformly linearly polarized Gaussian beam; by varying the amplitudes of the two fields, we control the formation of pairs of these singular points and their spatial separation. We complete this study by applying the same analysis to vector vortex beams with higher topological charges, and by investigating the features that arise when increasing the intensity of the Gaussian term. Our results can find application in the context of singularimetry, where weak fields are measured by considering them as perturbations of unstable optical beams.
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: D'Errico
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Maffei
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Piccirillo
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.|CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.
authors.forename: Corrado
authors.initials: C
authors.lastname: de Lisio
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Cardano
authors.affiliation: Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant'Angelo, Napoli, Italy.|CNR-ISASI, Institute of Applied Science and Intelligent Systems, Via Campi Flegrei 34, Pozzuoli (NA), Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Marrucci