高阶相对论谐波辐射的理论研究

对短脉冲强激光在非稠密均匀等离子体中传播时产生的相对论相干谐波辐射进行了一般性研究．在准稳态近似（ｑｕａｓｉｓｔａｔｉｃ ａｐｐｒｏｘｉｍａｔｉｏｎ）下得出ｎ阶谐波包络的演化方程，并用此方程研究了ｎ阶谐波的增长与饱和及转化效率等问题     

多原子分子中化学键的选择断裂

用最佳控制理论得到了波包激发的最优化光场的一般形式。控制方程用Ｈｉｌｂｅｒｔ空间波函数演化的形式写出，计算了选择断裂ＨＯＤ分子中ＯＨ键和ＯＤ键的最优化光场。     

螺旋相位调制型轨道角动量光束倍频及传播特性

通过分析螺旋相位调制型携带轨道角动量(OAM)光场的传播演化特性,提出一种以该光场演化波源为对象进行非线性效应研究的新途径。基于三波耦合模型和柯林斯路径积分理论,得到以OAM演化波源为基频光的二次谐波光场及衍射传播解析表达式。采用飞秒钛宝石激光器,基于4f相干成像系统,将OAM演化波源成像于倍频晶体处,实验研究了该波源产生的二次谐波的传播特性,测量了不同阶数OAM波源的倍频输出功率,并与演化后的OAM模式倍频结果进行了比较。研究表明,以演化波源附近为非线性作用区有望解决高维OAM模式光斑过大,以及光场交叠性不好导致的非线性效率低等问题,这也为高维OAM光场实现高效率非线性调控提供了重要依据。     

电子等离子体波对超短脉冲激光传播过程的作用

提出等离子体波对光脉冲产生相位调制的观点,把光脉冲在背景等离子体波中传播时的频率移动与脉宽压缩效应统一起来。给出了脉宽演化的方程,它类似于在势阱中运动的经典粒子的能量守恒方程;估算了脉宽压缩对应的等离子体波振幅阈值。数值计算进一步证实这些结论。最后指出实验上用等离子体波压缩短脉冲激光脉宽的可能性。 关键词：     

交叉传播相对论强激光脉冲在等离子体中相互作用及其对电子加热和加速的作用

文章介绍了相干交叉传播的相对论强激光在与等离子体相互作用中产生的能量交换、瞬态电子密度调制和激光加速电子，这些被加速的电子先在交叉光场中被捕获，随后又注入到等离子体波中，获得进一步的加速．这些现象最近在作者的实验研究和数值模拟中被观察到．     

光束三阶非线性效应的混沌理论研究

介质的三阶非线性性质会引起光场的非线性相移,而这类介质中当光强及介质的特性参数满足一定条件时,可以使光场的演化进入混沌的状态。从麦克斯韦方程组出发,推导了基于介质三阶非线性效应的麦克斯韦-布洛赫方程,并将其转化为归一化的洛伦兹方程形式。利用此方程,数值模拟了光场稳态及混沌态的演化过程。研究结果表明,三阶非线性介质中光场的演化可以进入混沌状态,这种状态对于控制材料中如自聚焦等有害的三阶非线性效应是不利的。     

GHZ类态原子体系与相干态光场相互作用的光场压缩特性

本文采用求解Schr dinger方程和数值计算的方法,研究了处于GHZ类态的三个全同二能级纠缠原子与相干态光场相互作用的光场压缩特性,结果表明:光场压缩量随时间的演化关系与三原子体系纠缠度和相干态光场的光场强度相关.在光场较弱、纠缠度较小时,可出现光场压缩现象;光场的增强或纠缠度的增加,都会使光场压缩现象消失.     

多能级原子与多模光场的相互作用机理研究

研究了多能级原子与多模光场的相互作用.探讨了旋波近似下N能级原子与(N-1)模光场相互作用演化规律，给出了相互作用绘景中其相应的Schrdinger方程的解析通式，分析了三能级原子、四能级原子分别与双模、三模光场相互作用的演化规律.研究结果表明：当原子初始时刻处于基态时，三能级原子与四能级原子的基态概率幅具有相同的变化规律. 关键词： 多能级原子 多模光场 旋波近似     

超短强激光脉冲在等离子体隧道中传输的理论与数值模拟研究

研究了超短强激光脉冲在非扰动抛物型部分电离的预等离子体隧道中的传输特性.从Maxwell方程出发得到了两个包含衍射、三阶强度非线性、等离子体散焦、等离子体隧道聚焦以及相对论自聚焦等效应在内的激光场演化方程，即折射率方程和哈密顿-雅可比方程.在此基础 上得到了激光在等离子体隧道中传输的包络方程以及光斑半径与传输距离、隧道宽度等初始 参量的关系. 关键词： 等离子体隧道聚焦 相对论自聚焦 势阱     

圆偏振强激光场下等离子体动力学方程及输运

将Ｆｏｋｋｅｒ－Ｐｌａｎｃｋ方程转换到电子在激光场中振荡的坐标中，得到了光场作用下的电子动力学方程；给出了圆偏振激光场作用下的电子－离子、电子－电子碰撞项；在不同的场强区域讨论了等离子体热电输运．研究表明，当电子在激光场的颤动速度接近或者大于其热运动速度时，与没有激光场情况相比，等离子体的热电输运减小很多． 关键词：     

Relativistic Self-Focusing of Short-Pulse Radiation Beams in Plasmas

An envelope equation is derived which describes the radial evolution of a radiation beam propagating through a plasma. The radiation envelope equation contains a defocusing term due to diffraction spreading and a focusing term due to relativistic oscillations of the plasma electrons. The case of a constant density background plasma is analyzed in detail and an expression for a critical laser power is derived. For powers exceeding the critical power, the radiation envelope oscillates and does not diffract. Under certain conditions the radiation beam propagates through the plasma with a constant radius envelope.     

One-dimensional EM solitons in ultrashort intense laser pulse-partially stripped plasmas

The one-dimensional electromagnetic (EM) envelope solitons in ultrashort intense laser pulse-partially stripped plasmas were discussed based on the wave equation of intense laser pulse propagating in partially stripped plasmas. Under the weakly relativistic assumption, a modified nonlinear Schrödinger (NLS) equation describing the evolution of the EM field was derived. The analytical analysis shows that in the ultra-short broad beam limits, the relativistic nonlinearity and striction nonlinearity cancel each other, and a one-dimensional laser pulse envelope soliton can be formed only due to the polarization nonlinearity. The relationship between the characteristics of soliton and the parameters of laser pulse and partially stripped plasmas was discussed by numerical analysis.     

Modulation instability of intense laser beam in an electron-positron plasma

Modulation instability of an intense right-hand elliptically polarized laser beam propagating through an electron-positron plasma is investigated by a new method. The nonlinear dispersion relation, in which the relativistic and ponderomotive nonlinearities are taken into account, is obtained for the laser radiation in electron-positron plasma by the Lorentz transformation. The Karpman equation is generalized to the case of three dimensions with three field components. When the nonlinear frequency shift of the electromagnetic field in plasma is involved, the nonlinear evolution equation for the slowly varying envelope of the laser field is obtained. Thus, modulation instability of the intense laser beam in electron-positron plasma is studied and the temporal growth rate of the instability is derived. The analysis shows that the growth rate of modulation instability is increased significantly near the critical surface in a laser-plasma.     

Modulation instability by intense laser beam in magnetized plasma

Modulation instability of an intense right-hand elliptically polarized laser beam propagating through magnetized plasma is investigated by a new method. The nonlinear dispersion relation, in which the relativistic and ponderomotive nonlinearities are taken into account, is obtained for the laser radiation in magnetized plasma by the Lorentz transformation. The Karpman equation is firstly generalized to the case of three dimensions with three field components. When the nonlinear frequency shift of the electromagnetic field in plasma is involved, the nonlinear evolution equation for the slowly varying envelope of the laser field is obtained. Thus, modulation instability of the intense laser beam in magnetized plasma is studied and the temporal growth rate of the instability is derived. The analysis shows that the peak growth rate of self-modulation instability is increased due to the axial magnetization of plasma. It is also shown that the growth rate of modulation instability is increased significantly near the critical surface in a laser-plasma.     

Dissipative Nonlinear Schrödinger Equation with External Forcing in Rotational Stratified Fluids and Its Solution

The dissipative nonlinear Schrödinger equation with a forcing item is derived by using of multiple scales analysis and perturbation method as a mathematical model of describing envelope solitary Rossby waves with dissipation effect and external forcing in rotational stratified fluids. By analyzing the evolution of amplitude of envelope solitary Rossby waves, it is found that the shear of basic flow, Brunt-Vaisala frequency and β effect are important factors in forming the envelope solitary Rossby waves. By employing Jacobi elliptic function expansion method and Hirota's direct method, the analytic solutions of dissipative nonlinear Schrödinger equation and forced nonlinear Schrödinger equation are derived, respectively. With the help of these solutions, the effects of dissipation and external forcing on the evolution of envelope solitary Rossby wave are also discussed in detail. The results show that dissipation causes slowly decrease of amplitude of envelope solitary Rossby waves and slowly increase of width, while it has no effect on the propagation speed and different types of external forcing can excite the same envelope solitary Rossby waves. It is notable that dissipation and different types of external forcing have certain influence on the carrier frequency of envelope solitary Rossby waves.     

强迫耗散与β效应地形效应作用下的非线性Rossby波包

正压流体中,从有外源的准地转位涡方程出发采用摄动方法和时空伸长变换推导了具有β效应、地形效应和外源的强迫Rossby孤立波包方程,得到孤立Rossby波振幅的演变满足带有地形与外源强迫的非齐次非线性Schrödinger方程的结论. 通过分析孤立Rossby波包振幅的演变,指出了β效应、地形效应以及外源都是诱导Rossby孤立波产生的重要因素,说明了在地形强迫效应和非线性作用相平衡的假定下,Rossby孤立波包振幅的演变满足非齐次非线性Schrödinger 关键词： Rossby波包 β效应')" href="#">β效应 地形 Schrödinger方程     

Steady state self-focusing, self-modulation of laser beam in an inhomogeneous plasma

Laboratory as well as PIC simulation experiments reveal strong flow of energetic electrons co-moving with laser beam in laser plasma interaction. Equation governing the evolution of complex envelope in slowly varying envelope approximation is nonlinear parabolic equation. Variational approach is used to solve this problem and a Lagrangian for the problem is set up. Assuming a trial Gaussian profile, authors solve the reduced Lagrangian problem for beam width and curvature. Two scale lengths for inhomogenity along the direction of propagation, one for nonlinearity and other for diffraction management are introduced. Self-focusing, self-modulation as well as self-trapping of the laser-electron-beam plasma system is studied under variety of parameters.     

Localized patterns and hole solutions in one-dimensional extended systems

The existence, stability properties, dynamical evolution and bifurcation diagram of localized patterns and hole solutions in one-dimensional extended systems are studied from the point of view of front interactions. An adequate envelope equation is derived from a prototype model that exhibits these particle-like solutions. This equation allows us to obtain an analytical expression for the front interaction, which is in good agreement with numerical simulations.     

Intense laser beam guiding in self-induced electron cavitation channel in underdense plasmas

In underdense plasmas, the transverse ponderomotive force of an intense laser beam with Gaussian transverse profile expels electrons radially, and it can lead to an electron cavitation. An improved cavitation model with charge conservation constraint is applied to the determination of the width of the electron cavity. The envelope equation for laser spot size derived by using source-dependent expansion method is extended to including the electron cavity. The condition for self-guiding is given and illuminated by an effective potential for the laser spot size. The effects of the laser power, plasma density and energy dissipation on the self-guiding condition are discussed.