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Phase-matched extreme-ultraviolet frequency-comb generation

Nature Photonicsvolume 12pages387391 (2018) | Download Citation


Laser-driven high-order harmonic generation1,2 provides spatially3 and temporally4 coherent tabletop sources of broadband extreme-ultraviolet (XUV) light. These sources typically operate at low repetition rates, frep 100 kHz, where phase-matched HHG is readily achieved5,6. However, many applications demand the improved counting statistics or frequency-comb precision afforded by high repetition rates, frep > 10 MHz. Unfortunately, at such high frep, phase matching is prevented by steady-state plasma accumulated in the generation volume7,8,9,10,11, strongly limiting the XUV average power. Here, we use high-temperature gas mixtures as the generation medium to increase the gas translational velocity, thereby reducing the steady-state plasma in the laser focus. This allows phase-matched XUV emission inside a femtosecond enhancement cavity at frep = 77 MHz, enabling a record generated power of ~ 2 mW in a single harmonic order. This power scaling opens up many demanding applications, including XUV frequency-comb spectroscopy12,13 of few-electron atoms and ions for precision tests of fundamental physical laws and constants14,15,16,17,18,19,20.

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This work was supported by the Air Force Office of Scientific Research grant FA9550-15-1-0111, National Institute of Standards and Technology and the National Science Foundation Physics Frontier Center at JILA (PHY-1734006). C.M.H. was supported by the Swedish Research Council. K.L.C. acknowledges the support of the JILA Visiting Fellows Program.

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Author notes

  1. These authors contributed equally: Gil Porat, Christoph M. Heyl, Stephen B. Schoun.


  1. JILA, NIST and the University of Colorado, Boulder, CO, USA

    • Gil Porat
    • , Christoph M. Heyl
    • , Stephen B. Schoun
    • , Craig Benko
    • , Kristan L. Corwin
    •  & Jun Ye
  2. Department of Physics, Lund University, Lund, Sweden

    • Christoph M. Heyl
  3. University of Vienna, Faculty of Physics, VCQ, Vienna, Austria

    • Nadine Dörre
  4. Department of Physics, Kansas State University, Manhattan, KS, USA

    • Kristan L. Corwin


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All authors contributed to the design, planning and execution of the experiment. G.P., C.M.H., S.B.S., C.B. and J.Y. analysed the data. All authors contributed to the writing of the manuscript.

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The authors declare no competing interests.

Corresponding authors

Correspondence to Gil Porat or Jun Ye.

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