强激光脉冲在部分离化等离子体中的自聚焦

采用变分法推导出有限长激光脉冲在部分离化等离子体中的参数演化方程，其中包含群速度色散和自相位调制的影响，通过分析焦斑半径和脉冲宽度满足的耦合方程，详细讨论了等离子体密度对激光脉冲传播特性影响。研究结果表明:在部分离化等离子体中，对于给定强度的激光脉冲，随着等离子体密度增大，自相位调制会进一步增强激光脉冲的自聚焦；当等离子体密度增大时，激光脉冲传播频率由负向啁啾变化转变为正向啁啾频率变化，而且随着传播距离增大，激光脉冲红移减小而蓝移增大。研究结果对有限长激光脉冲电离诱导自注入加速电子的方案具有理论指导意义。

The Self-Focusing of a Short Laser Pulses in Partially Stripped Plasma

In the presence of self-phase modulation,and group velocity dispersion,the propagation characteristics of a short laser pulse in partially stripped plasma are investigated. A variational technique is used to obtain equations describing the evolution of the laser spot size and pulse length,analyzing the effects of the plasma density on the propagation of a short laser pulse in partially stripped plasma. It is found that the laser pulse can be allowed to prop-agate in patitally stripped plasma only when a certain relation for laser parameters and plasma parameters is satis-fied. The plasma density has affected the laser focusing enhanced efficiently. As compared to fully ionized plasma,in partially stripped plasma,plasma density play a critical role of the laser focusing. The results may be significant the-oretically to the mechanism of ionization-induced injection and acceleration by an intense laser pulse.