Femtosecond self mode locking of Yb:fluoride phosphate glass laser

Passive cw mode locking of an ytterbium-doped fluoride phosphate glass laser is demonstrated, for what we believe to be the first time, based solely on the Kerr effect in the active medium in a resonator with dispersion compensation. Nearly bandwidth-limited pulses as short as 160fs are generated at ~1040 nm. We obtain average output powers as high as 250mW at 170-MHz repetition rate with absorbed pump power as low as 1.2W.