Dense pair plasma generation and its modulation dynamics in counter-propagating laser field

With two-dimensional quantum electrodynamics (QED) particle-in-cell simulations, a dense electron-positron (e^-e⁺) pair generation from laser-solid interactions is demonstrated. When the interaction of two linearly polarized laser pulses with a thin target enters into the relativistic transparency regime, a stable standing wave (SW) field can be formed by the overlap of the two counter-propagating laser pulses directly. The present study aims to clarify the effects of the SW field on the dynamics of e^-e⁺ pair plasmas. Our results indicate that under the combined effect of the SW field and radiation reaction (RR) effect, the created e^-e⁺ pairs can be trapped into the electric field nodes when the field strength is strong. The trapping effect contributes to the generation of γ_AV ≥ 400 and ultra-dense pair plasmas in the two-side irradiation scheme. Despite different laser intensities, these pair plasmas have a Maxwellian spectral distribution with a peak energy of 150 MeV. Besides, the periodical modulation of the average energy, spatial, phase-space, and angular patterns of the e^-e⁺ pair plasmas can be triggered. In the angular patterns, as long as the SW field exists, pair plasmas can be pinched along the laser polarization direction. These results may offer a better understanding of the laser-solid interactions in the experiments when 10-PW laser facilities come into operation in the future.