Generation of 12 fs deep-ultraviolet pulses by four-wave mixing through filamentation in neon gas

Generation of deep-ultraviolet femtosecond pulses by four-wave mixing through filamentation in neon gas was demonstrated. Fundamental (ω) and second-harmonic (2ω) pulses of 25 fs Ti:sapphire amplifier output were focused into neon gas, and 20μJ pulses with the center wavelength of 260 nm were produced by a four-wave mixing process, 2ω+2ω− ω→3ω through an ~15 cm filament. Additionally, pulses with an energy of 2μJ at 200 nm were generated, probably by a cascaded process, 3ω+2ω− ω→4ω. The 260 nm pulses were compressed by a grating-based compressor and characterized by a dispersion-free transient grating frequency-resolved optical gating. The estimated pulse width was 12 fs.