Efficient nonlinear compression of a thin-disk oscillator to 8.5 fs at 55 W average power

We demonstrate an efficient hybrid-scheme for nonlinear pulse compression of high-power thin-disk oscillator pulses to the sub-10 fs regime. The output of a home-built, 16 MHz, 84 W, 220 fs Yb:YAG thin-disk oscillator at 1030 nm is first compressed to 17 fs in two nonlinear multipass cells. In a third stage, based on multiple thin sapphire plates, further compression to 8.5 fs with 55 W output power and an overall optical efficiency of 65% is achieved. By sending the 2.5-cycle pulses into a lithium iodate crystal, we were able to generate ultra-broadband mid-infrared pulses covering the spectral range 2.4-8 $\mu$m.