Towards critical and supercritical electromagnetic fields

TL;DR

This paper explores how future high-power laser facilities could generate electromagnetic fields approaching the Schwinger critical field, enabling laboratory studies of extreme quantum phenomena previously thought unattainable.

Contribution

It proposes combining multiple colliding laser pulses with frequency upshifting to overcome cascade generation barriers, potentially reaching critical field strengths with 10-PW lasers.

Findings

10-PW lasers could reach Schwinger critical field strengths

Combining laser techniques suppresses pair cascades

Enables laboratory study of extreme quantum phenomena

Abstract

The availability of ever stronger, laser-generated electromagnetic fields underpins continuing progress in the study and application of nonlinear phenomena in basic physical systems, ranging from molecules and atoms to relativistic plasmas and quantum electrodynamics. This raises the question: how far will we be able to go with future lasers? One exciting prospect is the attainment of field strengths approaching the Schwinger critical field $E_\text{cr}$ in the laboratory frame, such that the field invariant $E^2 - c^2B^2 > E_\text{cr}^2$ is reached. The feasibility of doing so has been questioned, on the basis that cascade generation of dense electron-positron plasma would inevitably lead to absorption or screening of the incident light. Here we discuss the potential for future lasers to overcome such obstacles, by combining the concept of multiple colliding laser pulses with that of frequency upshifting via a tailored laser-plasma interaction. This compresses the electromagnetic field energy into a region of nanometer size and attosecond duration, which increases the field magnitude at fixed power but also suppresses pair cascades. Our results indicate that 10-PW-class laser facilities could be capable of reaching $E_\text{cr}$. Such a scenario opens up prospects for experimental investigation of phenomena previously considered to occur only in the most extreme environments in the Universe.