title: High-order harmonic generation up to 250 eV from highly ionized argon.
abstract: We demonstrate the generation of very high-order harmonics, up to 250 eV, using argon gas. This extends by 100 eV the highest harmonics previously observed using Ar and exceeds the energies observed using any other medium besides helium. This advance is made possible by using a waveguide geometry to limit plasma-induced laser beam defocusing, making it possible to generate high harmonics from Ar ions. This work shows that high harmonic emission from ions can extend laser-based coherent up-conversion into the soft x-ray region of the spectrum.
authors.affiliation: JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Gibson
authors.forename: Ariel
authors.initials: A
authors.lastname: Paul
authors.forename: Nick
authors.initials: N
authors.lastname: Wagner
authors.forename: Ra'anan
authors.initials: R
authors.lastname: Tobey
authors.forename: Sterling
authors.initials: S
authors.lastname: Backus
authors.forename: Ivan P
authors.initials: IP
authors.lastname: Christov
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn