The generation of unexpected super-high energetic electrons at relativistic circularly polarized laser-solid interactions in the presence of large scale pre-plasmas

TL;DR

This study demonstrates that circularly polarized lasers interacting with pre-formed plasmas can generate super-high energetic electrons, exceeding energies from linearly polarized lasers, due to envelope modulation effects.

Contribution

It reveals the role of envelope modulation in CP laser interactions, leading to higher electron energies and introduces a modified acceleration scaling law.

Findings

Super-high energy electrons (up to 120 MeV) generated with CP lasers.

Envelope modulation enhances electron acceleration compared to LP lasers.

A two-stage acceleration model explains the observed phenomena.

Abstract

As an extension of the previous work [arXiv: 1512.02411], we have investigated the role of circularly polarized (CP) laser pulses while keeping other conditions the same. It is found that in the presence of large scale pre-formed plasmas, super-high energetic electrons can be generated at relativistic CP laser-solid interactions. For laser of intensity $10^{20}\ \text{W}/\text{cm}^2$ and pre-plasma scale-length $10\ \mu\text{m}$, the cut-off energy of electron by CP laser is $120\ \text{MeV}$ compared with $100\ \text{MeV}$ in the case of linearly polarized (LP) laser. The unexpected super-high energetic electron acceleration can also be explained by the two-stage acceleration model, {by taking into account the envelop modulation effects of the reflected CP laser pulse.} The underlying physics of this envelop modulation is figured out, and a modified first-stage electron acceleration scaling law in the presence of the modulated-CP laser is also obtained.