title: Bright, coherent, ultrafast soft X-ray harmonics spanning the water window from a tabletop light source.
abstract: We demonstrate fully phase-matched high harmonic emission spanning the water window spectral region important for nano- and bioimaging and a breadth of materials and molecular dynamics studies. We also generate the broadest bright coherent bandwidth (≈300  eV) to date from any light source, small or large, that is consistent with a single subfemtosecond burst. The harmonic photon flux at 0.5 keV is 10³ higher than demonstrated previously. This work extends bright, spatially coherent, attosecond pulses into the soft x-ray region for the first time.
authors.affiliation: JILA, University of Colorado at Boulder, 80309-0440, USA.
authors.forename: M-C
authors.initials: MC
authors.lastname: Chen
authors.forename: P
authors.initials: P
authors.lastname: Arpin
authors.forename: T
authors.initials: T
authors.lastname: Popmintchev
authors.forename: M
authors.initials: M
authors.lastname: Gerrity
authors.forename: B
authors.initials: B
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Seaberg
authors.forename: D
authors.initials: D
authors.lastname: Popmintchev
authors.forename: M M
authors.initials: MM
authors.lastname: Murnane
authors.forename: H C
authors.initials: HC
authors.lastname: Kapteyn