High-order harmonic generation at a megahertz-level repetition rate directly driven by an ytterbium-doped-fiber chirped-pulse amplification system

We report the first experimental demonstration (to our knowledge) of high-order harmonic generation in rare gases driven by a state-of-the-art high-power Yb-doped-fiber chirped-pulse amplification system. The fiber laser delivers 270 fs pulses in the 30-100 mu J energy range at repetition rates varying from 100 kHz to 1 MHz. A proper focalization allows reaching several 10(13) W/cm(2) in a gas jet. We have been able to produce and detect harmonies up to order 31 (33.2 nm) in Ar at a 100 kHz repetition rate. High-order harmonic generation at 1 MHz is also demonstrated in Xe up to harmonic 15. The demonstrated extreme LTV (XUV) source will bring ultrashort XUV coincidence experiments from synchrotron facilities to tabletop laboratories. (C) 2009 Optical Society of America