Laser-pulse-shape control of seeded QED cascades

TL;DR

This paper demonstrates that laser pulse shaping can control QED cascades, either suppressing or facilitating them at ultra-high intensities, enabling new experiments in extreme quantum vacuum conditions.

Contribution

It introduces methods to control QED cascades using laser pulse shape and focusing, opening pathways for advanced high-intensity laser experiments.

Findings

QED cascades can be prevented at ~10^{26} W/cm^2 with focused, low-Z gases.

Cascades can be facilitated below 10^{24} W/cm^2 with larger focal areas or high-Z gases.

Control over QED cascades enables new plasma generation and vacuum instability studies.

Abstract

QED cascades are complex avalanche processes of hard photon emission and electron-positron pair creation driven by ultra-strong electromagnetic fields. They play a fundamental role in astrophysical environments such as a pulsars' magnetosphere, rendering an earth-based implementation with intense lasers attractive. In the literature, QED cascades were also predicted to limit the attainable intensity in a set-up of colliding laser beams in a tenuous gas such as the residual gas of a vacuum chamber, therefore severely hindering experiments at extreme field intensities. Here, we demonstrate that the onset of QED cascades may be either prevented even at intensities around $10^{26}\text{ W/cm$^{2}$}$ with tightly focused laser pulses and low-$Z$ gases, or facilitated at intensities below $10^{24}\text{ W/cm$^{2}$}$ with enlarged laser focal areas or high-$Z$ gases. These findings pave the way for the control of novel experiments such as the generation of pure electron-positron-photon plasmas from laser energy, and for probing QED in the extreme-intensity regime where the quantum vacuum becomes unstable.