title: Phase-coherent frequency combs in the vacuum ultraviolet via high-harmonic generation inside a femtosecond enhancement cavity.
abstract: We demonstrate the generation of phase-coherent frequency combs in the vacuum utraviolet spectral region. The output from a mode-locked laser is stabilized to a femtosecond enhancement cavity with a gas jet at the intracavity focus. The resulting high-peak power of the intracavity pulse enables efficient high-harmonic generation by utilizing the full repetition rate of the laser. Optical-heterodyne-based measurements reveal that the coherent frequency comb structure of the original laser is fully preserved in the high-harmonic generation process. These results open the door for precision frequency metrology at extreme ultraviolet wavelengths and permit the efficient generation of phase-coherent high-order harmonics using only a standard laser oscillator without active amplification of single pulses.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, 80309-0440, USA. rjjones@jilau1.colorado.edu
authors.forename: R Jason
authors.initials: RJ
authors.lastname: Jones
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Moll
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thorpe
authors.forename: Jun
authors.initials: J
authors.lastname: Ye