65-fs Yb:CaF_2 laser mode-locked by semiconductor saturable absorber mirror

An Yb:CaF2 laser pumped by two 400-mW single-mode laser diodes at 976 nm is reported to generate Fourierlimited 65-fs pulses, the shortest to date achieved with a semiconductor saturable absorber mirror (SESAM) mode-locking and this laser material to date. With a multimode pump diode, we have demonstrated higher average output powers of up to 1.4 W with 87-fs pulses. Key to these successful results was the implementation of practical design guidelines allowing safe mode-locking operation without Q-switching instabilities, which appear to damage the SESAMs more easily in Yb:CaF2 oscillators compared to other Yb-doped materials.