Femtosecond oscillators based on Yb:SrF2 and Yb:CaF2

Yb-doped calcium fluoride crystals have been demonstrated to be a very good candidate for the development of diode-pumped femtosecond lasers. In this paper, the development of short pulse oscillators based on Yb:CaF
₂
and Yb:SrF
₂
is presented. One challenge when developing short-pulsed oscillators with Yb-doped fluorides concerns the fact that they exhibit very long upper state life time (2.4 ms for Yb:CaF
₂
and 2.9 ms Yb:SrF
₂
) which counteract the stable modelocked operation in favour of Q-switch operation. Particular femtosecond modelocked regimes are studied in order to demonstrate sub-100-fs stable regime with Yb:CaF
₂
and femtosecond operation with Yb:SrF
₂
for the first time.