Sub-20 fs − 10.5 W Visible Pulse Generation from Yb-Doped Fiber Laser

High-power high-repetition rate femtosecond ytterbium-doped fiber lasers offer new perspectives in femtochemistry, solid-state physics and strong field physics. In particular, high-order harmonic generation (HHG) driven by Yb-fiber laser has demonstrated high photons flux in extreme ultraviolet (XUV) spectral range [1,2]. Shortening the laser pulse improves the achievable time resolution in pump-probe experiments and also the efficiency and the spectral extent of HHG (cutoff wavelength). However, the gain bandwidth of the Yb:fiber limits the pulse duration in the 250 fs-130 fs range. To solve this issue, nonlinear pulse compression experiments using Yb:fiber lasers have been carried out at the fundamental wavelength (1030 nm) to downscale the pulse duration in the 10 fs range [3,4]. On the other hand, so far the highest reported XUV photons flux up to milliwatt-class has been obtained at 515 nm driving wavelength with 11W-85 fs pulses [5]. While frequency doubling an ultrashort (<; 30 fs) pulse requires a trade-off between efficiency and pulse duration lengthening, we present in this work an efficient and high power sub-20 fs visible laser source based on the second harmonic generation (SHG) of a high energy Yb-doped femtosecond fiber laser followed by a nonlinear compression stage in a krypton-filled capillary.