Phase-matched extreme-ultraviolet frequency-comb generation

Author
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 of Publication
2018
Journal
Nature Photonics
Volume
12
Number of Pages
387-391
Date Published
2018-07
ISSN Number
1749-4885
URL
http://www.nature.com/articles/s41566-018-0199-z
DOI
10.1038/s41566-018-0199-z
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