title: Light trajectory in Bessel-Gauss vortex beams.
abstract: We investigate the early stage of propagation of Bessel-Gauss vortex beams where a transition regime shows a progressive lateral expansion of the main intensity ring before reaching a diffraction-free regime. The eikonal equation is used to characterize the beam structure. The beam is featured by a family of hyperboloids with variable waists, generating a tapered tubular caustic. Our analytical results are in excellent agreement with numerical and experimental results. We show the transition regime can be well eliminated by using hollow input beams.
authors.forename: Chen
authors.initials: C
authors.lastname: Xie
authors.forename: Remo
authors.initials: R
authors.lastname: Giust
authors.forename: Vytautas
authors.initials: V
authors.lastname: Jukna
authors.forename: Luca
authors.initials: L
authors.lastname: Furfaro
authors.forename: Maxime
authors.initials: M
authors.lastname: Jacquot
authors.forename: Pierre-Ambroise
authors.initials: PA
authors.lastname: Lacourt
authors.forename: Luc
authors.initials: L
authors.lastname: Froehly
authors.forename: John
authors.initials: J
authors.lastname: Dudley
authors.forename: Arnaud
authors.initials: A
authors.lastname: Couairon
authors.forename: Francois
authors.initials: F
authors.lastname: Courvoisier