共查询到18条相似文献,搜索用时 93 毫秒
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为深入研究黑腔内激光成丝不稳定性产生和发展,建立了空间束匀滑光束的传播模型,利用三维激光等离子体相互作用程序LAP3D模拟了黑腔物理条件下的大尺度成丝现象。模拟结果可正确描述成丝后光强的束发散现象及谱空间光强分布特征。从激光能量参数角度分析了导致成丝不稳定性发展的物理因素,并讨论了应用空间束匀滑技术抑制成丝不稳定性的局限性。研究表明:空间束匀滑光束发展成丝的能力取决于光斑内小焦斑的成丝表现,当具备成丝能力的小焦斑份额达到一定比例后,就会导致整个空间束匀滑光束成丝,因此对于光斑平均功率密度较高的光束,须考虑结合其他束匀滑手段来抑制成丝发展。 相似文献
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超快强激光在光学介质(如空气)中传播时由于克尔自聚焦效应和等离体散焦效应动态平
衡会发生一种独特的非线性激光成丝现象。激光成丝过程会诱导一些独特的物理现象,如非线性
光频转换产生超连续光谱、等离子体诱导高压放电、锥形辐射等,在大气传感、天气控制等研究
领域具有重要的应用前景。本文针对飞秒激光大气成丝过程中与传输介质相互作用所诱导的非线
性发光过程,介绍了激光大气成丝所产生的超连续光谱(白光)激光、谐波产生和太赫兹波辐射
三种非线性光频转换现象,并着重探讨了太赫兹波辐射的物理机理、研究现状和应用前景。 相似文献
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利用粒子模拟法对超强激光与等离子体相互作用中产生的Weibel不稳定性及其产生机制进行了详细的研究。给出不稳定性的线性色散关系和饱和磁场与各向异性参数之间的函数关系,发现Weibel不稳定性的存在使超强激光在等离子体中激发的自生磁场饱和,饱和自生磁场的存在使粒子速度分布在激光传播方向上表现出各向异性。讨论了Weibel不稳定性的线性和非线性饱和过程,对更好地理解快点火物理中自生磁场的产生、快电子输运等过程有重要意义。 相似文献
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The filamentation instability of laser beams propagating in nonlocal nonlinear media is investigated. It is shown that the filamentation instability can occur in weakly nonlocal self-focusing media for any degree of nonlocality, and in defocusing media for the input light intensity exceeding a threshold related to the degree of nonlocality. A linear stability analysis is used to predict the initial growth rate of the instability. It is found that the nonlocality tends to suppress filamentation instability in self-focusing media and to stimulate filamentation instability in self-defocusing media. Numerical simulations confirm the results of the linear stability analysis and disclose a recurrence phenomenon in nonlocal self-focusing media analogous to the Fermi-Pasta-Ulam problem. 相似文献
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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. 相似文献
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In this paper, we have examined the filamentation instability of laser radiation in a GaAs sample in the negative differential
resistivity region. A dc electric field is applied to assist the laser beam transferring electrons in the conduction band
from the lower valley to upper satellite valleys, i.e. in increasing the effective mass of electrons. The instability causes
the space charge perturbations in the microwave range of frequencies. The nonlinearity arises through the energy dependence
of the effective mass and the ponderomotive force on the electrons. The instability has finite frequency and possesses large
growth rate which is greatly influenced by the dc electric field. 相似文献
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R. Kh. Gainutdinov A. A. Mutydullina M. A. Khamadeev 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(3):272-275
The instability of an electron-positron vacuum in an intense laser field is studied. An equation describing the decay of the
electron-positron vacuum in the focal region of two strong opposing laser beams is derived on the basis of the generalized
dynamical equation. 相似文献
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We report on the first observations of periodic structures caused by the filamentation instability. These structures were observed on 0.35 μm laser irradiated planar target experiments. Comparison of these observations with self-focusing theory indicates that even though thermal filamentation may initiate the instability, ponderomotive force effects eventually dominate the actual filamentation process. 相似文献
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It is shown that the filamentation instability of a high frequency pump wave can have an exceptionally low threshold intensity in a magnetized plasma. The excitation of a purely growing mode may have important consequences in the laser heating schemes of pinch devices. 相似文献