Effect of electron heating on self-induced transparency in relativistic intensity laser-plasma interaction

TL;DR

This paper investigates how electron heating influences self-induced transparency in relativistic laser-plasma interactions, revealing that kinetic effects can significantly raise the effective critical density beyond cold-fluid predictions.

Contribution

It demonstrates that electron heating can substantially modify the transparency threshold, highlighting the importance of kinetic effects in relativistic laser-plasma interactions.

Findings

Electron heating increases the effective critical density.

Kinetic effects cause deviations from cold-fluid model predictions.

Electron escape into vacuum triggers laser pulse propagation.

Abstract

The effective increase of the critical density associated with the interaction of relativistically intense laser pulses with overcritical plasmas, known as self-induced transparency, is revisited for the case of circular polarization. A comparison of particle-in-cell simulations to the predictions of a relativistic cold-fluid model for the transparency threshold demonstrates that kinetic effects, such as electron heating, can lead to a substantial increase of the effective critical density compared to cold-fluid theory. These results are interpreted by a study of separatrices in the single-electron phase space corresponding to dynamics in the stationary fields predicted by the cold-fluid model. It is shown that perturbations due to electron heating exceeding a certain finite threshold can force electrons to escape into the vacuum, leading to laser pulse propagation. The modification of the transparency threshold is linked to the temporal pulse profile, through its effect on electron heating.