Electron acceleration in direct laser-solid interactions far beyond the ponderomotive limit

TL;DR

This paper demonstrates that using radially polarized laser pulses on wire targets can significantly surpass the ponderomotive limit of electron energy through enhanced direct laser acceleration, revealing new effects and efficiencies.

Contribution

The study introduces a novel method of breaking the ponderomotive limit using radially polarized pulses and shows the role of anti-dephasing and plasma effects in electron acceleration.

Findings

Anti-dephasing enhances electron energy by two orders of magnitude.

Radially polarized pulses produce more super-ponderomotive electrons than linear or circular pulses.

Collective plasma effects are crucial for energy enhancement.

Abstract

In laser-solid interactions, electrons may be generated and subsequently accelerated to energies of the order-of-magnitude of the ponderomotive limit, with the underlying process dominated by direct laser acceleration. Breaking this limit, realized here by a radially-polarized laser pulse incident upon a wire target, can be associated with several novel effects. Three-dimensional Particle-In-Cell simulations show a relativistic intense laser pulse can extract electrons from the wire and inject them into the accelerating field. Anti-dephasing, resulting from collective plasma effects, are shown here to enhance the accelerated electron energy by two orders of magnitude compared to the ponderomotive limit. It is demonstrated that ultra-short radially polarized pulses produce super-ponderomotive electrons more efficiently than pulses of the linear and circular polarization varieties.