Direct Measurement of the XUV Frequency Comb Coherence

ORAL

Abstract

We present the first demonstration of XUV radiation with phase coherence capable of reaching sub-kHz resolution. The XUV comb is produced by frequency up conversion of a near-infrared frequency comb by intra-cavity high harmonic generation (HHG). Using an 80 W Yb:fiber fs frequency comb, we simultaneously pump two femtosecond enhancement cavities to reach intensities suitable for HHG. The harmonics are out-coupled from the cavities using sapphire plates placed at Brewster angle for the pump laser. We developed an interferometer capable of operating in the XUV and measured a heterodyne beat between the two sources at different harmonics. Despite being insensitive to common-mode pump laser noise, the heterodyne beats will reveal any noise added by the intra-cavity HHG process. This will allow us to probe the fundamental limit on the coherence properties of HHG.

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Authors

  • Craig Benko

    JILA, NIST, University of Colorado, Boulder

  • Thomas K. Allison

    JILA, NIST, University of Colorado, Boulder

  • Arman Cingoz

    JILA, NIST, University of Colorado, Boulder

  • Dylan C. Yost

    JILA, NIST, University of Colorado, Boulder

  • Jun Ye

    JILA, NIST, University of Colorado, Boulder, JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, CO 80309, USA, JILA/University of Colorado at Boulder, JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, Boulder, CO, JILA, University of CO, Boulder and NIST, JILA, NIST and University of Colorado-Boulder, and Department of Physics, University of Colorado-Boulder, JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, JILA, NIST, and University of Colorado-Boulder