Nonlinear propagation effect in x-ray parametric amplification during high harmonic generation

TL;DR

This study demonstrates nonlinear effects in x-ray parametric amplification during high harmonic generation, revealing how plasma dispersion influences amplification dynamics and periodicity.

Contribution

It provides the first experimental and numerical analysis of nonlinear propagation effects in x-ray parametric amplification in high harmonic generation.

Findings

Parametric amplification occurs within a few optical cycles.

Unusual one optical cycle periodicity observed in XUV intensity modulation.

Plasma dispersion causes nonlinear effects affecting amplification dynamics.

Abstract

We report the realization and characterization of parametric amplification in high harmonic generation around 100 eV using He gas in a double gas jet arrangement. The delay of the seed XUV pulse with respect to the amplifier gas jet was scanned by changing the distance between the gas jets. Experiments and numerical calculations show that parametric amplification occurs within a temporal window of several optical cycles. Strong correlation between the seed and amplifier was observed in a shorter, few optical cycles delay range, which appeared as a modulation of the XUV intensity with an unexpected one optical cycle periodicity instead of half optical cycle. Simulations revealed that the strong correlation and also the unusual periodicity was the consequence of the nonlinear effect produced by plasma dispersion on the parametric amplification process during propagation in the amplifier jet.