Widely tunable sub-30 fs ultraviolet pulses by chirped sum frequency mixing.

A novel scheme for the generation of UV pulses in the 295 - 450 nm range is presented. Sum frequency mixing of the chirped visible pulses from a noncollinear optical parametric amplifier with deliberately chirped pulses from the Ti:sapphire amplifier ensures efficient energy conversion and easy tunability. Pulse energies as high as 5.5 J at 295 nm, and >2 J in most of the tuning range are obtained with highly symmetric and smooth spectra. They are compressed to sub-30 fs throughout the entire tuning range (20 fs at 348 nm) with a newly designed prism compressor.