Laser absorption via QED cascades in counter propagating laser pulses

TL;DR

This paper presents a self-consistent model and simulations of laser energy absorption in electron-positron plasmas created via QED cascades, highlighting the dependence on laser intensity and pulse duration, with absorption reaching up to 80% at extreme intensities.

Contribution

The study introduces a comprehensive model combined with advanced simulations to analyze laser absorption through QED cascades, including a macro-particle merging algorithm for handling exponential particle growth.

Findings

Absorption negligible at ~10 PW laser intensity.

Absorption reaches up to 80% at >100 PW.

Good agreement between analytical model and simulations.

Abstract

A model for laser light absorption in electron-positron plasmas self-consistently created via QED cascades is described. The laser energy is mainly absorbed due to hard photon emission via nonlinear Compton scattering. The degree of absorption depends on the laser intensity and the pulse duration. The QED cascades are studied with multi-dimensional particle-in-cell simulations complemented by a QED module and a macro-particle merging algorithm that allows to handle the exponential growth of the number of particles. Results range from moderate-intensity regimes ($\sim$ 10 PW) where the laser absorption is negligible, to extreme intensities (> 100 PW) where the degree of absorption reaches 80%. Our study demonstrates good agreement between the analytical model and simulations. The expected properties of the hard photon emission and the generated pair-plasma are investigated, and the experimental signatures for near-future laser facilities are discussed.