Asymmetry in laser wakefields driven by intense pulses

TL;DR

This paper derives an exact analytical formula for the transverse momentum of electrons in laser wakefields, revealing asymmetries not captured by traditional symmetric models, and explains observed simulation results.

Contribution

It introduces a fundamental approach to accurately describe electron transverse momentum beyond the envelope approximation in laser wakefield theories.

Findings

Exact formula for electron transverse momentum along the axis

Explanation of strong wakefield asymmetry in simulations

Enhanced understanding of electron motion inside intense laser pulses

Abstract

Laser wakefield theories rely on the laser envelope function, which is radially symmetric, and predict zero transverse momentum for the electrons along the propagation axis. Exact description of laser wakefields, beyond the envelope approximation, requires a more general formula for the Lorentz force acting on the electrons. Here we present a fundamental approach to express the transverse momentum of an electron crossing the laser pulse, and we show that an exact analytical formula can be derived for the non-zero transverse momentum of electrons initially lying along the axis of symmetry. The results outlined here shed light on the details of the electron motion inside an intense laser pulse and explain the strong wakefield asymmetry observed in simulations.