High-repetition-rate cw-pumped Cr3 +:LiSrAlF 6 femtosecond regenerative amplifier

We have developed a cw krypton-ion-laser-pumped Cr3 +:LiSrAlF6 regenerative amplifier for femtosecond pulses operating at a 5-kHz repetition rate. After recompression, we obtained 3.6-,uJ, 170-fs pulses at 825 nm. By focusing these pulses in a cell of water, we generated a white-light continuum. Since its first demonstration by Payne et al. ' at the Lawrence Livermore National Laboratory, the Cr3+:LiSrAlF6 (Cr:LiSAF) crystal has proved to be a promising laser medium. This crystal combines a large fluorescence bandwidth (750-950 nm) with an absorption band in the red between 600 and 700 nm, making it particularly suitable for the de-velopment of an all-solid-state diode-pumped tunable laser. Owing to its extremely large emission band, Cr:LiSAF is well suited to the generation and amplifi-cation of ultrashort pulses. In fact, self-mode-locked femtosecond oscillators2'3 and flash-lamp regenera