Observation of parametric amplification with a femtosecond vacuum-ultraviolet four-wave difference-frequency mixing source

The high conversion efficiency of the Xe-atom four-wave difference-frequency mixing (ω = ω1- ω2) vacuum UV (VIJV) femtosecond source relies on a coincidental near two-photon resonance occurring when the l light pulses are at 248.5 nm. It also depends on the coherence properties of the input pulses. As in previous studies of this system, high-intensity femtosecond light pulses at ω1were produced by amplification in a KrF-excimer discharge, but the required 248.5-nm seed pulses were obtained from a new source based on near-threshold continuum generation. Nonlinear mixing in Xe of the pulses prepared at ωl with femtosecond visible light pulses of ω2 yielded ω2 - ω3 energy conversions of -1 and VUV pulse energies as high as 60 AuJ. At low input energies the beam at ω2 was observed to be parametrically amplified by a factor 150. © 1994 Optical Society of America.