Filamentation-assisted plasma lifetime measurements in atomic and molecular gases via third-harmonic enhancement

We present lifetime measurements of femtosecond laser-induced plasma in atomic and molecular gases via enhanced third-harmonic radiation from a filament. So far, only the plasma lifetime of air has been measured with this approach. We report and analyze the first measurements for other gases, including, to the best of our knowledge, the first-ever documented temporal evolution measurement of femtosecond laser-induced plasma in helium. We show that the temporal plasma evolution is imprinted directly in our measurement traces without the need of any further assumptions or data treatment. (C) 2019 Optical Society of America