Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases

Abstract

We study numerically low-order harmonic generation in noble gases pumped by intense femtosecond laser pulses in the tunneling ionization regime. We analyze the influence of the phase-mismatching on this process, caused by the generated plasma, and study in dependence on the pump intensity the origin of harmonic generation arising either from the bound-electron nonlinearity or the tunnel-ionization current. It is shown that in argon the optimum pump intensity of about 100 TW/cm${}^2$ leads to the maximum efficiency, where the main contribution to low-order harmonics originates from the bound-electron third and fifth order susceptibilities, while for intensities higher than 300 TW/cm${}^2$ the tunnel-ionization current plays the dominant role. Besides, we predict that VUV pulses at 133 nm can be generated with relatively high efficiency of about $1.5\times 10^{-3}$ by 400 nm pump pulses.

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References in corpus (2)

• Tailoring THz radiation by controlling tunnel photoionization events in gases
• Comparative investigation of third and fifth harmonic generation in atomic and molecular gases driven by mid-infrared ultrafast laser pulses

Cited by in corpus (1)

• High order Brunel harmonics and supercontinuum formed by a weak optical pump in presence of a strong terahertz field