Generation of Ultra-intense Gamma-ray Train by QED Harmonics

TL;DR

This paper demonstrates that at ultra-high laser intensities, QED effects dominate gamma-ray generation, producing high-energy, ultra-short gamma-ray trains with unique properties distinct from traditional HHG processes.

Contribution

It introduces a new regime of gamma-ray generation via QED harmonics at intensities above 10^22 W/cm^2, highlighting the role of QED effects in high-order harmonic processes.

Findings

Gamma-ray train period is half of the laser period.

Peak gamma-ray intensity reaches 1.4×10^22 W/cm^2.

QED harmonics are typically incoherent and random.

Abstract

When laser intensity exceeds 10^22W/cm^2, photons with energy above MeV can be generated from high-order harmonics process in the laser-plasma interaction. We find that under such laser intensity, QED effect plays a dominating role in the radiation pattern. Contrast to the gas and relativistic HHG processes, both the occurrence and energy of gamma-ray emission produced by QED harmonics are random and QED harmonics are usually not coherent, while the property of high intensity and ultra-short duration is conserved. Our simulation shows that the period of gamma-ray train is half of the laser period and the peak intensity is 1.4e22W/cm^2. This new harmonic production with QED effects are crucial to light-matter interaction in strong field and can be verified in experiments by 10PW laser facilities in the near future.