Laser-cluster interaction in an external magnetic field: the effect of laser polarization

TL;DR

This paper investigates how circularly polarized laser fields influence electron dynamics in laser-cluster interactions within an external magnetic field, building on previous work with linear polarization to explore new absorption mechanisms and electron behaviors.

Contribution

It introduces the study of circular polarization effects on laser-cluster interactions in magnetic fields, extending prior linear polarization research to reveal new electron dynamics and absorption characteristics.

Findings

Circular polarization alters electron energy absorption patterns.

Electron energy increases significantly with circular polarization.

Electron beam angular spread remains narrow (<5°) with circular polarization.

Abstract

Collisionless absorption of laser energy by an electron via laser-cluster interaction in an ambient magnetic field ($B_0$) has recently renewed interest. %due to high levels of absorption. Previously, using a rigid sphere model (RSM) and an extensive particle-in-cell (PIC) simulation with linearly polarized (LP) laser light, we have shown that an auxiliary field $B_0$ in a transverse direction to the laser polarization significantly enhances the laser absorption [Scientific Reports {\bf 12}, 11256 (2022)]. In this LP case, the average energy ($\mathcal{E}_A$) of an electron rises near $30-70$ times of its ponderomotive energy ($U_p$). The two-stage laser absorption by cluster electrons has been attributed via anharmonic resonance (AHR) followed by electron-cyclotron resonance (ECR) satisfying the improved phase-matching and frequency-matching conditions simultaneously. %Again, we report the narrow cone-like propagation of these %energetic electron bunches as a weakly relativistic electron beam with an %angular spread $\Delta\theta<5^{\circ}$. %Also, we highlight the effect of bigger cluster sizes on the energy and %angular spread of these electrons. In the present work, we study the effect of circularly polarized (CP) laser fields on the cluster-electron dynamics considering left/right circular polarizations with an ambient $B_0$. %, energy distribution, and..