摘要
激光在等离子体中传播时,横等离激元与驱动的离子声波发生调制相互作用,出现调制不稳定性。随着调制不稳定性的非线性发展,将使得激光场峰值越来越大,最终导致激光场的坍塌。利用电磁波在等离子体中的非线性色散关系以及Karpman方程,首次得到在一般情况下调制不稳定性的时间增长率与扰动态波数之间的函数关系。结果表明,调制不稳定性的时间增长率随着激光强度的增大而增长;越接近等离子体临界面处,调制不稳定的时间增长率的峰值显著增长。同时从线偏振激光场波包所满足的非线性控制方程出发,利用维里定理,讨论调制不稳定发展后期的波包坍塌动力学问题,证明了激光场具有塌缩行径。
When an incident laser beam propagates in plasma, there is modulation interaction between the transverse pumping plasmons and the driven ion-acoustic wave,and the modulation instability occurs. With the nonlinear development of modulation instability, the peak amplitude of the laser electric field is bigger and bigger, then it would lead to the collapse of the laser field. Based on the nonlinear dispersion relation of electromagnetic wave in plasma and Karpman equation, the function of temporal growth rate and perturba- tion wave number is generally obtained for the first time. The analysis shows that with the intensity of the laser electric field increasing, the temporal growth rate of the modulation instability will be increased. And the peak growth rate of modulation instability is increased significantly near the critical surface in a laser- plasma. On the basis of the nonlinear equation for the wave packet of the linearly polarized laser electric field, the collapse dynamics of the wave packet at the later stage of modulation instability is discussed by means of Virial theorem,and it is shown that the laser electric field possesses the collapsing behavior.
出处
《南昌大学学报（理科版）》
CAS
北大核心
2016年第5期455-458,492,共5页
Journal of Nanchang University(Natural Science)
基金
中国科学技术部国际科技合作项目(2015DFA61800)
江西省青年科学基金项目(20142BAB212008)
关键词
线偏振激光
等离子体
调制不稳定性
坍塌
Linearly polarized laser beam
Plasma
Modulation instability
Collapse
