EFFICIENT FEMTOSECOND PULSE GENERATION AT 264 NM

We have experimentally demonstrated the generation of a powerful femto second pulse at 264 nm, starting with a picosecond pulse from a Nd:gla ss laser and using a nonlinearly compressed second-harmonic pulse. Fou rth-harmonic pulses with durations between 130-370 fs have been genera ted in KDP and BBO crystals of various lengths. The consistency of the numerical and experimental data indicates that group-velocity mismatc h and two-photon absorption are the main factors limiting the efficien cy of the frequency quadrupling process with femtosecond pulses.