Single-laser scheme for reaching strong field QED regime via direct laser acceleration

TL;DR

This paper proposes a feasible single-laser scheme using direct laser acceleration and reflection to reach the strong-field QED regime, enabling high-energy photon emission and pair production with current multi-petawatt lasers.

Contribution

It introduces a novel single-laser setup combining DLA and reflection to efficiently generate QED effects at lower laser powers.

Findings

A 2 PW laser can reach the quantum regime with $> 1$.

Positron yield exceeds 2 nC at 10 PW laser power.

The scheme's efficiency depends on laser depletion and foil positioning.

Abstract

We investigate a single-laser scheme for reaching the strong-field QED regime based on direct laser acceleration (DLA) of electrons followed by their head-on collision with the same laser pulse reflected from an overdense foil. In this configuration, electrons are first accelerated inside an underdense plasma by a relativistic laser pulse and subsequently interact with the reflected laser field, emitting high-energy photons via nonlinear Compton scattering which decay into electron-positron pairs through the nonlinear Breit-Wheeler process. Using analytical scalings supported by quasi-3D particle-in-cell simulations including QED effects, we demonstrate that a laser pulse with power as low as 2 PW is sufficient to reach the quantum regime characterized by $\chi_e> 1$ . For higher powers, we observe a rapid nonlinear increase in the number of generated positrons, reaching more than 2 nC for a 10 PW laser pulse with energy of approximately 1.1 kJ. A semi-analytical model is employed to estimate the positron yield, showing good agreement with simulation results. We further study the influence of laser depletion and the positioning of the reflecting foil on the efficiency of pair production. The presented scheme provides an experimentally feasible platform for probing strong-field QED effects using currently available multi-petawatt laser systems.