MHz repetition rate Yb:YAG disk laser-amplifier for transform limited pulses, tunable between 10 ps and 100 ps

Special laser applications ranging from laser material processing, especially micromachining, to medical applications, metrology and spectroscopy demand transform limited ps pulses, often synchronized with a fs source [1]. Here, we present spectral compression of fs pulses inside a regenerative Yb:YAG laser amplifier [2] generated by a mode-locked Yb:KGW oscillator (see Fig. 1a). For spectral shaping we used an intra-cavity monochromator (grating, imaging lens and slit), while temporal and spectral tunability is achieved by insertion of a movable slit in the Fourier domain. A tuning range between 1025 and 1033 nm in spectral domain and between 3 and 100 ps in temporal domain was demonstrated (see Fig. 1b). We verified that the achieved time-bandwidth product (TBP) for all pulse durations >10 ps were kept close to the minimum of 0.44 (for Gaussian shaped pulses, see Fig. 1c).