Diode-pumped 99 fs Yb:CaF2 oscillator

We demonstrate the generation of 99 fs pulses by a mode-locked laser oscillator built around a Yb:CaF2 crystal. An average power of 380 mW for a 13 nm bandwidth spectrum centered at 1053 nm is obtained. The short-pulse operation is achieved thanks to a saturable absorber mirror and is stabilized by the Kerr lens effect. We investigated the limits of the stabilization process and observed a regime slowly oscillating between mode locking and Q switching