title: Stable radially symmetric and azimuthally modulated vortex solitons supported by localized gain.
abstract: We discover that a spatially localized gain supports stable vortex solitons in media with cubic nonlinearity and two-photon absorption. The interplay between nonlinear losses and gain in amplifying rings results in the suppression of otherwise ubiquitous azimuthal modulation instabilities of radially symmetric vortex solitons. We find that the topology of the gain profile imposes restrictions on the maximal possible charge of vortex solitons. Symmetry breaking occurs at high gain levels, resulting in the formation of necklace vortex solitons composed of asymmetric bright spots.
authors.affiliation: ICFO-Institut de Ciencies Fotoniques and Universitat Politecnica de Catalunya, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain.
authors.forename: Valery E
authors.initials: VE
authors.lastname: Lobanov
authors.forename: Yaroslav V
authors.initials: YV
authors.lastname: Kartashov
authors.forename: Victor A
authors.initials: VA
authors.lastname: Vysloukh
authors.forename: Lluis
authors.initials: L
authors.lastname: Torner