摘要： The recent development of high repetition rate lasers based on ytterbium-doped fiber amplifiers (YDFA), has paved the way to increase the repetition rate (>100 kHz) of coherent extreme ultra violet (XUV) sources generated by high harmonic generation (HHG). High repetition rate HHG driver comes with several advantages, such as increased photon flux [1], reduction of the acquisition time in coincidence experiments to study molecular dynamics such as COLTRIMS, and the possibility to study the electronic structure of matter via photoemission spectroscopy and microscopy, where low doses are needed to avoid space-charge effects [2]. Up to now, the overall majority of HHG studies and applications has been restricted to the low repetition rates of Ti:sapphire lasers. Commonly, Ti:sapphire lasers delivers 20 fs pulses at a central wavelength λ = 800 nm, with pulse energies up to hundreds of mJ. However, the average power of these laser systems cannot easily be scaled beyond 10 W, restricting HHG at low repetition rates (up to 10 kHz). Currently, the most mature and powerful ultrafast source technology is undoubtedly ytterbium-based systems, with average power levels beyond 1 kW [3] and numerous industrial applications. However, the long pulse duration of around >200 fs delivered by YDFA sources limits their relevance to this application field. Therefore, nonlinear compression setups have been used successfully to reduce the pulse duration and obtain XUV photon flux among the highest ever reported for HHG-based sources [1]. However, to reach sub-3 cycles regime (< 10 fs at 1030 nm), which is typically required in combination with gating techniques to obtain isolated attosecond pulses, two stages of compression must usually be implemented [4]. This reduces the energy efficiency of the systems dedicated to attosecond physics to typically less than 30% of the overall YDA energy. Here, we demonstrate a two-cycle-source based on a high-energy femtosecond YDFA followed by a hybrid two-stage nonlinear compression setup. The association of a multipass cell-based stage and large-diameter capillary stage provides a compression factor of 48 with an overall transmission of 61%. This source is, to the best of our knowledge, the most efficient few cycle, high energy and high repetition rate laser demonstrated to date. It is very compact with an overall footprint of 1.8 m × 1.0 m and provides a stable train of few-cycle pulses at a central wavelength of 1030 nm that has been continuously characterized over more than 8h. The delivered 6.8 fs (see Fig. 1) 140 μJ pulses at 150 kHz repetition rate, corresponding to 21 W average power, are ideally suited to drive high-photon flux XUV sources [5] through HHG. The described laser system is robust, compact, and power efficient, making it an ideal driver laser for application-ready high flux XUV and attosecond sources.