Laser wakefield acceleration driven by few-cycle laser pulses in overdense plasmas

TL;DR

This study demonstrates that few-cycle laser pulses interacting with overdense plasmas can generate energetic electron beams via laser wakefield acceleration, revealing new physics in ultrashort pulse regimes.

Contribution

It provides the first experimental evidence and numerical confirmation that few-cycle laser pulses can resonantly excite plasma wakefields in overdense plasmas, enabling relativistic electron acceleration.

Findings

Electron beams are produced only with <10 fs pulses and large plasma scale lengths.

Plasma waves are resonantly excited by few-cycle pulses in near-critical-density regions.

Electrons are injected by ionization and accelerated to relativistic energies.

Abstract

We measure the emission of energetic electrons from the interaction between ultrashort laser pulses and a solid density plasma in the relativistic regime. We detect an electron beam that only appears with few-cycle pulses (< 10 fs) and large plasma scale lengths ($L > \lambda_0$). Numerical simulations, in agreement with the experiments, reveal that these electrons are accelerated by a laser wakefield. Plasma waves are indeed resonantly excited by the few-cycle laser pulses in the near-critical-density region of the plasma. Electrons are then injected by ionization into the plasma waves and accelerated to relativistic energies. This study provides an unprecedented insight into the physics happening in the few-cycle regime.