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

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 ( E A ) 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 3 U p or less) by an electron. However, with B0, CP light enhances the electron's energy further by ≈ 10 − 20 U p beyond the previously reported values ≈ 30 − 70 U p by the LP light. These ejected electrons from cluster show narrow cone-like propagation as a weakly relativistic electron beam with an angular spread Δ θ < 5 ° and the beam quality improves in CP than LP. In all cases, RSM and PIC results show good agreement. [ABSTRACT FROM AUTHOR]