Laser–cluster interaction in an external magnetic field: The effect of laser polarization

Abstract

Collisionless absorption of laser energy by an electron via laser–cluster interaction in an ambient magnetic field (B0) has recently renewed interest. 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 B0 in a transverse direction to the laser polarization significantly enhances the laser absorption [Swain et al., Sci. Rep. 12, 11256 (2022)]. In this LP case, the average energy (EA) of an electron rises nearly 30−70 times of its ponderomotive energy (Up). 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. 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 B0. In typical conditions, without B0, we show that both LP and CP light yield almost the same level of laser absorption (about 3Up or less) by an electron. However, with B0, CP light enhances the electron's energy further by ≈10−20Up beyond the previously reported values ≈30−70Up by the LP light. These ejected electrons from cluster show narrow cone-like propagation as a weakly relativistic electron beam with an angular spread Δθ<5° and the beam quality improves in CP than LP. In all cases, RSM and PIC results show good agreement.