We investigate the terahertz (THz) wave emission from air plasma by analyses and simulations. An elliptically polarized THz wave is generated, whereas a circularly polarized carrier-envelope phase (CEP) stabilized few-cycle laser pulse is applied. Its ellipticity and intensity depend on the pulse duration of the driving laser pulse. And the polarization rotates along the CEP of the driving laser pulse. The THz generation is also simulated for different filament lengths. As the filament extends, the polarization of the generated THz wave rotates along the filament.

在超短强激光与固体薄膜靶相互作用产生高能离子的研究领域内，由于靶后静电场持续时间较长、离子具有较好的准直性及单能性，靶后鞘层加速(TNSA)机制一直都是研究重点。介绍了TNSA 机制的理论模型、近期的实验结果以及模拟验证，并系统讨论了通过结构优化得到高质量离子束的方案，最后综述了近期国内外利用TNSA 机制加速离子的研究进展。

提出了一种基于平方证据权重的模糊证据组合方法,并应用于弱小目标多特征融合检测算法中,采用了证据理论中的基本概率分配函数来描述判决结果的不确定性,首先提取检测图像的局部灰度均值对比度、局部梯度均值对比度、局部差值和局部熵四个特征,然后对特征进行归一化,再对其进行模糊化并根据先验知识和测量统计的结果对目标各特征值所取空间和待识别目标假设集进行基本概率分配,接着采用自适应加权融合的方法得到目标的基本可信度,最后采用基于博弈概率分布的决策规则得到检测后的目标图像。实验结果表明,该算法能在较大程度上降低目标检测过程中的不确定性,提高系统的检测性能。

Electron acceleration by a propagating short ultra-intense laser pulse in a low-density plasma has been investigated. Electrons have the maximum energy when meeting the peak of the laser pulse. If a propagating laser pulse is abruptly stopped by a solid target, the highly energetic electrons will continue to move forward inertially and escape from the laser field. The envelope of the laser pulse is taken into account and there is an optimal position between the electron and the solid target. The electron maximum energy depends on the laser intensity and initial electron energy, and has nothing to do with the polarization of the pulse, but a linearly polarized laser pulse is more effective to accelerate electron than circularly polarized one under the same laser energy. The influence of the reflected light has been taken into account which makes our model more perfect and the results give good agreement with particle in cell simulations.

We present the study of the interaction of an intense circularly polarized pulse with a solid target with one-dimensional (1D) particle-in-cell (PIC) simulation. The evolvement of ion motion with time is explained by a purely kinetic description and by the theory of electrostatic shock in collisionless plasmas. Especially the formation of the stable profile with a "double-flat-top" in ion phase space is explained and validated visually. Assuming the initial state, we find that the ion distribution in the phase space agrees qualitatively with the PIC simulation results by using the particle-tracing approach.

Two-dimensional particle-in-cell simulations are taken to study the interaction of a relativistic, circularly polarized laser pulse with a preformed overdense plasma channel containing a slice of micron size. The laser pulse is confined in the channel, so it can keep higher intensity on a longer time scale inside the channel than the case without a channel. The electrons, both in the slice and from the channel, are pushed forward in the channel by the large light pressure of the laser pulse, followed by the ions accelerated by the electro static field generated by the charge separation. As a result, the acceleration of the slice is more efficient and has a better collimation than in the case without a preformed channel.