The propagation of ultra-intense circularly polarized laser pulses in a relativistically transparent plasma is investigated with the help of particle-in-cell (PIC) simulations. When the incident laser pulse is strong enough to expel almost all electrons from the focal volume, the propagation of the laser front edge is found to be dominated by the balance between the laser radiation pressure and the laser-driven electrostatic pressure. Based on a one-dimensional (1D) model, the laser front edge velocity is predicted to depend on $n_0/a_0n_c$, where $n_0$ is the initial plasma density, $n_c$ the critical density, and $a_0$ the laser amplitude. PIC simulations show that the theoretical prediction works well for not only 1D but also 2D and 3D geometries.

中文翻译：

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相对论透明等离子体中超强圆偏振激光脉冲的前沿速度

借助细胞内粒子 (PIC) 模拟，研究了超强圆偏振激光脉冲在相对论透明等离子体中的传播。当入射激光脉冲足够强以将几乎所有电子从焦点体积中排出时，发现激光前沿的传播受激光辐射压力和激光驱动静电压力之间的平衡支配。基于一维 (1D) 模型，预测激光前沿速度取决于 $n_0/a_0n_c$，其中 $n_0$ 是初始等离子体密度，$n_c$ 是临界密度，$a_0$ 是激光振幅。PIC 模拟表明，理论预测不仅适用于 1D，而且适用于 2D 和 3D 几何。