Investigating the influence of ionization on high-harmonic generation in Ar–Ne and Ar–Kr gas mixtures driven by kHz laser pulses

We conducted a study on high-harmonic generation (HHG) in mixed gases, specifically Ar–Ne or Ar–Kr, with the aim of investigating the impact of ionization rate and neutral dispersion on the HHG process. Our focus was on understanding how these factors influence the HHG process when using gases with low and high ionization potentials. Based on phase-matched high-order harmonic generation in pure Ar gas, our investigation shows that the influence of plasma dispersion and neutral dispersion can be varied independently in mixed gas while the laser intensity is kept constant. Our results reveal that the addition of low ionization potential gases, such as Kr, to the Ar gas leads to a more rapid reduction in phase matching, due to the strong effects of ionization. The observed experimental outcomes align well with our theoretical calculations. This study provides valuable insights into the interplay of ionization rate and neutral dispersion in high-harmonic generation and the special requirement of the controlling of laser intensity for phase-matched harmonic generation. The findings contribute to a deeper understanding of the underlying dynamics and offer practical considerations for optimizing HHG properties.

Graphical abstract