title: Tunable orbital angular momentum in high-harmonic generation.
abstract: Optical vortices are currently one of the most intensively studied topics in optics. These light beams, which carry orbital angular momentum (OAM), have been successfully utilized in the visible and infrared in a wide variety of applications. Moving to shorter wavelengths may open up completely new research directions in the areas of optical physics and material characterization. Here, we report on the generation of extreme-ultraviolet optical vortices with femtosecond duration carrying a controllable amount of OAM. From a basic physics viewpoint, our results help to resolve key questions such as the conservation of angular momentum in highly nonlinear light-matter interactions, and the disentanglement and independent control of the intrinsic and extrinsic components of the photon's angular momentum at short-wavelengths. The methods developed here will allow testing some of the recently proposed concepts such as OAM-induced dichroism, magnetic switching in organic molecules and violation of dipolar selection rules in atoms.
authors.affiliation: Elettra-Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Gauthier
authors.affiliation: Elettra-Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy.
authors.forename: P Rebernik
authors.initials: PR
authors.lastname: Ribič
authors.affiliation: Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia.
authors.forename: G
authors.initials: G
authors.lastname: Adhikary
authors.affiliation: Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: A
authors.initials: A
authors.lastname: Camper
authors.affiliation: LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: C
authors.initials: C
authors.lastname: Chappuis
authors.affiliation: Elettra-Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Cucini
authors.affiliation: Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: L F
authors.initials: LF
authors.lastname: DiMauro
authors.affiliation: Imagine Optic, 91400 Orsay, France.
authors.forename: G
authors.initials: G
authors.lastname: Dovillaire
authors.affiliation: Institute of Photonics and Nanotechnologies, CNR-IFN, 35131 Padova, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Frassetto
authors.affiliation: LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: R
authors.initials: R
authors.lastname: Géneaux
authors.affiliation: Institute of Photonics and Nanotechnologies, CNR-IFN, 35131 Padova, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Miotti
authors.affiliation: Institute of Photonics and Nanotechnologies, CNR-IFN, 35131 Padova, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Poletto
authors.affiliation: Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia.
authors.forename: B
authors.initials: B
authors.lastname: Ressel
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, 91405 Orsay, France.
authors.forename: C
authors.initials: C
authors.lastname: Spezzani
authors.affiliation: Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia.
authors.forename: M
authors.initials: M
authors.lastname: Stupar
authors.affiliation: LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: T
authors.initials: T
authors.lastname: Ruchon
authors.affiliation: Elettra-Sincrotrone Trieste, Area Science Park, 34149 Trieste, Italy.|Laboratory of Quantum Optics, University of Nova Gorica, 5001 Nova Gorica, Slovenia.
authors.forename: G
authors.initials: G
authors.lastname: De Ninno