Influence of gas pressure on high-order harmonic generation of Ar and Ne

TL;DR

This paper investigates how gas pressure influences high-order harmonic generation in argon and neon, using advanced theoretical models and simulations to understand the pressure-dependent spectral features.

Contribution

It combines quantitative rescattering theory with Maxwell's wave equation simulations to analyze pressure effects on harmonic generation, highlighting the importance of focusing conditions.

Findings

Harmonic spectra are highly sensitive to focusing conditions at high pressure.

Simulated spectra qualitatively match experimental pressure dependence.

Fundamental laser field reshaping significantly affects harmonic generation.

Abstract

We study the effect of gas pressure on the generation of high-order harmonics where harmonics due to individual atoms are calculated using the recently developed quantitative rescattering theory, and the propagation of the laser and harmonics in the medium is calculated by solving the Maxwell's wave equation. We illustrate that the simulated spectra are very sensitive to the laser focusing conditions at high laser intensity and high pressure since the fundamental laser field is severely reshaped during the propagation. By comparing the simulated results with several experiments we show that the pressure dependence can be qualitatively explained. The lack of quantitative agreement is tentatively attributed to the failure of the complete knowledge of the experimental conditions.