Generation of sub-20-fs, two-color deep-ultraviolet pulses by four-wave mixing through filamentation in gases

Abstract

Generation of ultrashort pulses at 260 nm and 200 nm by four-wave mixing through filamentation in neon gas was demonstrated. Fundamental (ω1) and second-harmonic (ω2) pulses of 25 fs Ti:sapphire laser output were focused into neon gas, and 260 nm (ω3) pulses were produced by a four-wave mixing process, ω2 + ω2 − ω1 → ω3, through an ~15 cm filament. At the same time, 200 nm (ω4) pulses were also genereted by a cascaded process, ω3 + ω2 − ω1 → ω4, and/or by a sum frequency process, ω2 + ω1 + ω1 → ω4. The both pulses were simultaneously compressed by a grating-based compressor, and characterized by a trangient grating frequencyresolved optical gating. The estimated pulse widths of the 260 nm and 200 nm pulses were 14 fs and 16.5 fs, respectively.