相对论效应对激光在等离子体中的共振吸收的影响

采用一维粒子模拟(PIC)方法，研究了相对论效应对P偏振激光斜入射非均匀等离子体时产生的共振吸收的影响. 计算表明，弱相对论情况下，在临界面附近产生的电子等离子体波的相对论非线性效应占主要作用；随着入射光场的逐渐增大，吸收率逐渐降低. 当入射光强超过3.7×10¹⁷W/cm²时，由于超短激光脉冲本身在等离子体中产生相对论效应、等离子体波破裂效应，以及参量不稳定过程激发等，吸收系数随着激光强度又开始增加. 固定等离子体密度标长，取不同的激光入射角、电子初始温度，相对论效应对吸收系数的影响是一致的. 关键词： 激光等离子体 相对论效应 共振吸收 粒子模拟

Relativistic effects on resonance absorption in laser-plasma interaction

The relativistic effects on resonance absorption, occurring when a high intensity p-polarized laser pulse is incident obliquely onto inhomogeneous plasma, are discussed by use of one-dimensional particle-in-cell simulation. It is found that the absorption rate decreases with the increase of the amplitude of the incident pulse until the laser intensity reaches about 3.4×10¹⁷W/cm². This is mainly owing to the relativistic effect of the electrostatic field driven near the critical surface. At high light intensities, because of the relativistic effect of the laser pulse itself in plasma the plasma wave breaking, and the excitation of the parameter instabilities, the absorption begins to increase with the light intensity. For a given scale-length, similar intensity-dependence of the absorption is found for different incident angles and different initial electron temperatures.