Sub-50 fs, Kerr-lens mode-locked Yb:CaF2 laser oscillator delivering up to 2.7 W

By means of a high-brightness optical pumping scheme with a fiber laser, we demonstrate Kerr-lens mode locking (KLM) with an Yb:CaF2 laser crystal. Stable 48 fs pulses are produced at an average power of 2.7 W.