Tunable 30-femtosecond pulses across the deep ultraviolet

Intense femtosecond pulses in the deep ultraviolet are generated by phase-matched four-wave mixing in an argon-filled hollow waveguide using 100-fs pulses from a commercial Ti:sapphire regenerative amplifier. Despite the long duration driving pulses, pulses as short as 25fs with energies of >5μJ at 266nm are produced after a simple double-pass prism compressor. In combination with an infrared optical parametric amplifier, tunable pulses are obtained over the 224–240nm range with energies exceeding 1μJ, bandwidths of 5nm and typical compressed pulsewidths of 31fs. Excellent mode and stability make this a promising source for deep ultraviolet pump-probe experiments.