Hafizi B, Ting A, Sprangle P, Hubbard RF
Icarus Research, Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780, USA.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Sep;62(3 Pt B):4120-5. doi: 10.1103/physreve.62.4120.
The ponderomotive force associated with an intense laser beam expels electrons radially and can lead to cavitation in plasma. Relativistic effects as well as ponderomotive expulsion of electrons modify the refractive index. An envelope equation for the laser spot size is derived, using the source-dependent expansion method with Laguerre-Gaussian eigenfunctions, and reduced to quadrature. The envelope equation is valid for arbitrary laser intensity within the long pulse, quasistatic approximation and neglects instabilities. Solutions of the envelope equation are discussed in terms of an effective potential for the laser spot size. An analytical expression for the effective potential is given. For laser powers exceeding the critical power for relativistic self-focusing the analysis indicates that a significant contraction of the spot size and a corresponding increase in intensity is possible.
与强激光束相关的有质动力会沿径向驱出电子，并可能导致等离子体中的空化现象。相对论效应以及电子的有质动力驱出会改变折射率。利用具有拉盖尔 - 高斯本征函数的源相关展开方法，推导了激光光斑尺寸的包络方程，并将其简化为求积形式。该包络方程在长脉冲、准静态近似且忽略不稳定性的情况下，对任意激光强度均有效。根据激光光斑尺寸的有效势来讨论包络方程的解。给出了有效势的解析表达式。对于超过相对论自聚焦临界功率的激光功率，分析表明光斑尺寸可能会显著收缩，强度相应增加。
