高强度激光与等离子体相互作用中的受激Raman级联散射、光子凝聚以及大振幅电磁孤立子的产生与加速

Stimulated Raman cascade_into_photon condensation and ultra_intense EM solitons in laser plasma interaction

应用一维相对论电磁粒子模拟程序,详细研究了线性极化强激光入射到无碰撞稀疏密度长等离子体中引起的受激Raman散射、Raman级联散射、级联散射到光子凝聚、以及大振幅电磁孤立子的产生与加速.通过研究发现:在适当的激光振幅和等离子体状态下,强的光子凝聚现象会导致大振幅电磁孤立子的产生,电磁孤立子可以以静止、向后以及向前加速的形式存在;在密度均匀的等离子体中,电磁孤立子的加速不仅依赖于激光振幅而且依赖于等离子体的长度;电磁孤立子的电磁频率大约为未扰动电子等离子体振荡频率的二分之一左右,孤立子内电磁场的电场具有半周期结构,相应电磁场的磁场以及静电场则具有一个完整的周期结构.

Stimulated Raman scattering, stimulated Raman cascade and the transition from Raman cascade into photon condensation, induced by linearly-polarized intense laser beam interacting with underdense collisionless homogeneous plasmas, are studied by particle simulations. It is found that, at appropriate laser amplitude and plasma condition, a large-amplitude relativistic EM soliton is formed due to the strong photon condensation. The standing, backward- and forward-accelerated large-amplitude relativistic electromagnetic solitons induced by intense laser pulses in underdense collisionless homogeneous plasmas are studied by particle simulations. In addition to the inhomogeneity of the plasma density, we found that the acceleration of the solitons depends upon both the laser intensity and the plasma length. The electromagnetic frequency of the solitons is about one-half of the unperturbed electron plasma frequency. The transverse electric, magnetic and electrostatic fields have half-, one- and one-cycle structure in space, respectively.