近共振区超短强激光脉冲激发的等离子体尾波场

 用一维相对论粒子模拟研究了相对论超短强激光脉冲在等离子体中传播时激发的尾波场，初步获得了近共振区尾波场的峰值幅度随激光脉冲宽度变化的特点，发现在近共振区等离子体波激发出现增强。通过准静态近似下尾波激发的一维非线性方程数值求解，并与粒子模拟结果比较，得到了该非线性方程的适用范围：当激光脉冲宽度小于等离子体波波长的4倍时，该方程所得结果与粒子模拟结果一致；而当激光脉冲宽度大于该数值时，该方程不再适用。

Plasma wake field excited by an ultrashort intense laser pulse at near-resonant regime

In this paper we have studied the excitation of plasma wake field by an ultrashort laser pulse in the near-resonant regime through one-dimensional particle-in-cell (PIC) simulations. Preliminary results are given of the amplitude of the plasma wake field versus laser pulse duration from resonant to near resonant regime. It is found that the wake field excitation is enhanced at near-resonant regime. The wake field is also obtained by numerically solving a nonlinear equation, which have been used to study wake field excitation under quasi-static approximation. By comparing the results from the two methods, the appropriate region of using the nonlinear equation is established that the laser pulse duration has to be 4 times less than the plasma wave wavelength. For longer laser pulses, the nonlinear equation does not work any more.