共查询到18条相似文献,搜索用时 250 毫秒
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利用一维粒子模拟程序,观测到周期量级的超短激光脉冲在等离子体中可以以孤子形式传播.它在一定密度等离子体中以较高的群速度向前传播,并在到达等离子体与真空界面时发生反射和透射.当入射激光脉冲强度增大时,非线性调制效应使它产生较大的频率下移,致使光孤子传播速度变小.另外,对于同样光强下的几十个周期以上的光脉冲,它在等离子体中传播时形成的则是一连串低频的被捕获在等离子体中的光孤子.
关键词:
光孤子
超短激光脉冲
等离子体
粒子模拟 相似文献
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超短脉冲强光与等离子体相互作用是近年来令人注目的一个前沿领域。介绍了其中的超短脉冲强激光与非稠密等离子体作用中的激光尾波场与尾波场加速器、光脉冲频率上转换与脉宽正缩、相对论光导等重要研究课题。还介绍了超短脉冲强激光与固体靶作用听吸收机制,短标尺长等离子体产生、能量输运等有关问题的研究。 相似文献
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研制了激光等离子体二维相对论电磁粒子模拟程序(2DCIC)。追踪几万甚至百万个模拟粒子在外加激光场和自洽场中运动,自洽地计算电荷和电流密度,求解完全的Maxwel方程,电子的相对论运动方程和离子的牛顿运动方程,辅以灵活的诊断研究波-波,波-粒子相互作用的发生、发展和饱和的细节以及时间演化规律。激光可以正入射,也可以斜入射;等离子体可以是均匀密度,也可以具有密度梯度;为了节约机时,还发展了并行运算。物理模型参数可调,既适用于研究激光聚变等离子体相互作用,也适用于超短脉冲超强激光等离子体相互作用和其它等离子体问题。经过多次试算检验,对等离子体平衡态进行了计算研究,对于超短脉冲超强激光的传播也进行了初步模拟计算。 相似文献
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用一维粒子模拟研究了超短脉冲在等离子体中传播时产生的光孤子结构以及由此形成的脉冲分裂现象,比较了不同峰值强度和脉冲宽度对形成光孤子以及脉冲传播方式的影响.研究表明: 脉冲宽度在若干个到十几个振荡周期的超短脉冲在等离子体中可能形成高速传播的光孤子;脉冲宽度增加和强度增大两种方式都可以使得孤子结构的传播速度减慢,且由于高阶孤子的衰变使得初始激光脉冲在等离子体中发生分裂,形成两个以不同速度向前传播的孤子结构.由孤子阶数的理论计算可较好地预言激光脉冲在等离子体中分裂的子脉冲数.
关键词:
光孤子
超短激光脉冲
等离子体
粒子模拟 相似文献
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超短强激光脉冲在等离子体中传播时会激发大振幅的等离子体尾波场,它是一种电子等离子体波.由于这是一种静电波,它一般不能转换成电磁辐射.我们发现在不均匀等离子体中激发的尾波场在一定条件下可以通过线性模式转换产生电磁辐射.由于用超短强激光脉冲尾波场可以达到的电场振幅达100GV/m,其振动频率在太赫兹(10^12Hz)附近,用这种方法可以产生电场强度达到GV/m的太赫兹辐射. 相似文献
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介绍了超短脉冲超强激光等离子体中几种新的能量吸收机制。强激光照射等离子体时,相对论效应导致电子质量增大,相对论电子等离子体频率减小,激光能更深地进入等离子体产生强烈吸收。 相似文献
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在弱相对论条件下,给出了超短强激光脉冲在稀薄等离体中传播的孤子解及其所激发的尾波场孤子解。 相似文献
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A set of exact one-dimensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction
are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial
velocity. 相似文献
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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. 相似文献
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A linear theory on the propagation of ultrashort pulses including only a few cycles in underdense plasmas is presented. It is shown that the dispersion in plasmas causes severe distortions in the pulse shape, including pulse chirping and spreading. The analytical calculations coincide very well with those obtained by particle-in-cell (PIC) simulations. The upper limit of the peak amplitude of the pulses, above which the linear theory breaks down due to the setting in of nonlinear effects of both the relativistic electron-mass increase and ponderomotive force, is also examined by PIC simulations. At certain high amplitudes, it is found that the ultrashort laser pulses can propagate like solitons. 相似文献
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Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed. 相似文献
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Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed. 相似文献
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Large amplitude electromagnetic solitons in intense laser plasma interaction 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper shows that the standing, backward- and forward-accelerated large
amplitude relativistic electromagnetic solitons induced by intense laser pulse in
long underdense collisionless homogeneous plasmas can be observed by particle
simulations. In addition to the inhomogeneity of the plasma density, the
acceleration of the solitons also depends upon not only the laser amplitude but also
the plasma length. The electromagnetic frequency of the solitons is between about
half and one of the unperturbed electron plasma frequency. The electrostatic field
inside the soliton has a one-cycle structure in space, while the transverse electric
and magnetic fields have half-cycle and one-cycle structure respectively. Analytical
estimates for the existence of the solitons and their electromagnetic frequencies
qualitatively coincide with our simulation results. 相似文献
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应用一维相对论电磁粒子模拟程序,详细研究了线性极化强激光入射到无碰撞稀疏密度长等离子体中引起的受激Raman散射、Raman级联散射、级联散射到光子凝聚、以及大振幅电磁孤立子的产生与加速. 通过研究发现:在适当的激光振幅和等离子体状态下,强的光子凝聚现象会导致大振幅电磁孤立子的产生,电磁孤立子可以以静止、向后以及向前加速的形式存在;在密度均匀的等离子体中,电磁孤立子的加速不仅依赖于激光振幅而且依赖于等离子体的长度;电磁孤立子的电磁频率大约为未扰动电子等离子体振荡频率的二分之一左右,孤立子内电磁场的电场具有半周期结构,相应电磁场的磁场以及静电场则具有一个完整的周期结构.
关键词:
粒子模拟
受激Raman散射
Raman级联散射
光子凝聚
电磁孤立子 相似文献
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Based on computer simulation, we demonstrate the possibility of formation of solitons upon propagation of a femtosecond laser pulse in a medium containing gold nanoparticles in the presence of two-photon light absorption. The solitons are formed when the laser pulse induces a positive phase grating. The speed of solitons substantially exceeds the speed of laser radiation propagating in a linear medium. 相似文献