BROADLY TUNABLE FEMTOSECOND PULSE GENERATION IN THE NEAR AND MIDINFRARED

High-repetition-rate (80-MHz) femtosecond infrared pulses are generate d by difference frequency mixing (DFM) a femtosecond Ti:sapphire laser with a phase-locked synchronized cw mode-locked Nd:YAG picosecond las er. This DFM scheme is of particular interest for generating ultrashor t near-IR pulses (similar to 10 fs) because group velocity mismatch wi th a pump pulse can be ignored. The simplicity and the broad wavelengt h tunability (from the near IR to the mid-IR) of this scheme is demons trated. Short (125-fs FWHM) optical pulses in the near IR around 1.5 m u m are obtained with noncritical type-I phase-matched LiB3O5. We also used a similar scheme to generate mid-infrared pulses at 3.0 mu m wit h type-II phase-matched KTiOPO4. (C) 1997 Optical Society of America.