Sub-femtosecond electron bunches created by direct laser acceleration in a laser wakefield accelerator with ionization injection

TL;DR

This study demonstrates through 3D simulations that direct laser acceleration in laser wakefield accelerators can produce sub-femtosecond electron bunches, with micro-bunching occurring under specific laser pulse conditions.

Contribution

It reveals the conditions under which sub-femtosecond electron bunches are generated via direct laser acceleration with ionization injection.

Findings

Longer laser pulses fill the entire bubble and produce micro-bunching.

Sub-femtosecond electron bunches of 0.5 fs are achievable.

Shorter pulses do not produce micro-bunching.

Abstract

In this work, we will show through three-dimensional particle-in-cell simulations that direct laser acceleration in laser a wakefield accelerator can generate sub-femtosecond electron bunches. Two simulations were done with two laser pulse durations, such that the shortest laser pulse occupies only a fraction of the first bubble, whereas the longer pulse fills the entire first bubble. In the latter case, as the trapped electrons moved forward and interacted with the high intensity region of the laser pulse, micro-bunching occurred naturally, producing 0.5 fs electron bunches. This is not observed in the short pulse simulation.