@article{4303,
  author = {Gil Porat and Christoph Heyl and Stephen Schoun and Craig Benko and Nadine Dörre and Kristan Corwin and Jun Ye},
  title = {Phase-matched extreme-ultraviolet frequency-comb generation},
  abstract = {Laser-driven high-order harmonic generation provides spatially and temporally\ 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 achieved. 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 volume, 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 spectroscopy of few-electron atoms and ions for precision tests of fundamental physical laws and constants.},
  year = {2018},
  journal = {Nature Photonics},
  volume = {12},
  pages = {387-391},
  month = {2018-07},
  issn = {1749-4885},
  url = {http://www.nature.com/articles/s41566-018-0199-z},
  doi = {10.1038/s41566-018-0199-z},
}