Femtosecond modelocked lasers using new ytterbium-doped borate crystals (Yb:Sr3Y(BO3)3,
Yb:Ca4GdO(BO3)3 and Yb:Ca4YO(BO3)3) are demonstrated. Pulse duration as short as 69 fs
has been obtained. To modelock such lasers, fast saturable absorbers need to be used. Two
different types of fast saturable absorbers have been studied: low-temperature-grown
semiconductor mirrors (SESAM) and high-energy-ion-implanted semiconductor Bragg
reflectors (SBR). We demonstrated, for the first time to our knowledge, that ion-implanted
SBR can be used to modelock oscillators using Yb-doped materials.