title: High-order harmonic generation from ions in a capillary discharge.
abstract: We demonstrate a significant extension of the high-order harmonic cutoff by using a fully-ionized capillary discharge plasma as the generation medium. The preionized plasma dramatically reduces ionization-induced defocusing and energy loss of the driving laser due to ionization. This allows for significantly higher photon energies, up to 150 eV, to be generated from xenon ions, compared with the 70 eV observed previously. We also demonstrate enhancement of the harmonic flux of nearly 2 orders of magnitude at photon energies around 90 eV when the capillary discharge is used to ionize xenon, compared with harmonic generation in a hollow waveguide. The use of a plasma as a medium for high-order harmonic generation shows great promise for extending efficient harmonic generation to much shorter wavelengths using ions.
authors.affiliation: JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado, 80309-0440, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Gaudiosi
authors.forename: Brendan
authors.initials: B
authors.lastname: Reagan
authors.forename: Tenio
authors.initials: T
authors.lastname: Popmintchev
authors.forename: Michael
authors.initials: M
authors.lastname: Grisham
authors.forename: Mark
authors.initials: M
authors.lastname: Berrill
authors.forename: Oren
authors.initials: O
authors.lastname: Cohen
authors.forename: Barry C
authors.initials: BC
authors.lastname: Walker
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.forename: Jorge J
authors.initials: JJ
authors.lastname: Rocca