Plasma mirrors as a path to the Schwinger limit

TL;DR

This paper demonstrates that plasma mirrors created by ultra-intense lasers can significantly enhance laser intensity, paving the way to experimentally reach the Schwinger limit and test fundamental QED predictions.

Contribution

It provides the first all-optical measurement of plasma mirror effects, confirming their potential to achieve extreme laser intensities near the Schwinger limit.

Findings

Plasma mirrors can be produced by ionizing solid targets with ultra-intense lasers.

Reflected laser pulses are temporally compressed and spatially focused by plasma mirrors.

This technique enables reaching laser intensities approaching the Schwinger limit.

Abstract

Reaching light intensities above $10^{25}$ W/cm$^{2}$ and up to the Schwinger limit ($10^{29}$ W/cm$^{2}$) would enable testing decades-old fundamental predictions of Quantum Electrodynamics. A promising yet challenging approach to achieve such extreme fields consists in reflecting a high-power femtosecond laser pulse off a curved relativistic mirror. This enhances the intensity of the reflected beam by simultaneously compressing it in time down to the attosecond range, and focusing it to sub-micron focal spots. Here we show that such curved relativistic mirrors can be produced when an ultra-intense laser pulse ionizes a solid target and creates a dense plasma that specularly reflects the incident light. This is evidenced by measuring for the first time the temporal and spatial effects induced on the reflected beam by this so-called 'plasma mirror'. The all-optical measurement technique demonstrated here will be instrumental for the use of relativistic plasma mirrors with the emerging generation of Petawatt lasers, which constitutes a viable experimental path to the Schwinger limit.