Generation of high energy, sub-20-fs vacuum UV pulses by noncollinear four-wave-mixing in argon

Here we present the shortening of the VUV pulses to less than 20 fs by the application of sub-15-fs idler pulses provided by the use of nonlinear spectral broadening of the FF pulses during filamentation. The pump laser provides up to 3 mJ pulses at 800 nm with 40 fs duration. Using a 1:1 beam splitter (BS), 50% of the pulse energy is applied for spectral broadening in an argon filled gas cell at a pressure of 1.1 bar. After spectral broadening, the FF pulses are compressed to less then 15 fs using chirped mirrors.