共查询到20条相似文献,搜索用时 15 毫秒
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M. S. Bawa'aneh 《等离子体物理论文集》2003,43(7):447-455
Stimulated Brillouin backscattering (SBBS) from a magnetized homogeneous plasma is investigated. Effect of a dc–magnetic field on SBBS growth rate is obtained and compared with that for non–magnetized plasmas. Numerical calculations show an increase in the instability growth rate for small magnetic fields, then a decrease in the growth rate as the magnetic field increases till a cut–off field is reached, beyond which SBBS is brought to stability. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Wu Zhao-Hui Wei Xiao-Feng Zuo Yan-Lei Liu Lan-Qin Zhang Zhi-Meng Li Min Zhou Yu-Liang Su Jing-Qin 《中国物理 B》2015,24(1):14211-014211
Chirped wideband pump and seed pulses are usually considered for backward Raman amplification(BRA)in plasmas to achieve an extremely high-power laser pulse.However,current theoretical models only contain either a chirped pump or a chirped seed.In this paper,modified three-wave coupling equations are proposed for the BRA in the plasmas with both chirped wideband pump and seed.The simulation results can more precisely describe the experiments,such as the Princeton University experiment.The optimized chirp and bandwidth are determined based on the simulation to enhance the output intensity and efficiency. 相似文献
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用2660(?)的紫外激光解离PbCl_2分子时,发现在3740(?)和3734(?)波长上有较强的受激辐射输出.根据它们的光谱特性和铅原子的能级结构判断,这些辐射是基于双光子解离PbCl_2分子得到的铅原子在6p~(23)P_2亚稳能级上的布居而产生的光泵共振激光辐射和受激喇曼散射.提出了描述整个过程的理论模型,通过拟合实验结果,确定了2660(?)激光双光子解离PbCl_2产生6p~(23)P_2亚稳态铅原子的光解系数.当PbCl_2分子密度为N_(00)=6.21×10~(16)cm~(-3)时,光解产生的铅原子在6p~(23)P_2和6p~(21)D_2这两个亚稳态的最大布居数近似相等,称为2.0×10~(16)cm~(-3). 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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Post-solitons and electron vortices generated by femtosecond intense laser interacting with uniform near-critical-density plasmas 下载免费PDF全文
Dong-Ning Yue 《中国物理 B》2022,31(4):45205-045205
Generation of nonlinear structures, such as stimulated Raman side scattering waves, post-solitons and electron vortices, during ultra-short intense laser pulse transportation in near-critical-density (NCD) plasmas is studied by using multi-dimensional particle-in-cell (PIC) simulations. In two-dimensional geometries, both P- and S-polarized laser pulses are used to drive these nonlinear structures and to check the polarization effects on them. In the S-polarized case, the scattered waves can be captured by surrounding plasmas leading to the generation of post-solitons, while the main pulse excites convective electric currents leading to the formation of electron vortices through Kelvin-Helmholtz instability (KHI). In the P-polarized case, the scattered waves dissipate their energy by heating surrounding plasmas. Electron vortices are excited due to the hosing instability of the drive laser. These polarization dependent physical processes are reproduced in two different planes perpendicular to the laser propagation direction in three-dimensional simulation with linearly polarized laser driver. The current work provides inspiration for future experiments of laser-NCD plasma interactions. 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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Barbara Dunlap Peter Richter David W. McCamant 《Journal of Raman spectroscopy : JRS》2014,45(10):918-929
We present a detailed theoretical and experimental characterization of a new methodology for stimulated Raman spectroscopy using two duplicates of a chirped, broadband laser pulse. Because of the linear variation of laser frequency with time (‘chirp’), when the pulses are delayed relative to one another, there exists a narrow bandwidth, instantaneous frequency difference between them, which, when resonant with a Raman‐active vibration in the sample, generates stimulated Raman gain in one pulse and inverse Raman loss in the other. This method has previously been used for coherent Raman imaging and termed ‘spectral focusing’. Here, gain and loss signals are spectrally resolved, and the spectrally integrated signals are used to determine the spectral resolution of the measured Raman spectrum. Material dispersion is used to generate a range of pulse durations, and it is shown that there is only a small change in the magnitude of the signal and the spectral resolution as the pulse is stretched from 800 to 1800 fs in duration. A quantitative theory of the technique is developed, which reproduces both the magnitude and linewidth of the experimental signals when third‐order dispersion and phase‐matching efficiency are included. The theoretical calculations show that both spectral resolution and signal magnitude are severely hampered by the third‐order dispersion in the laser pulse, and hence, a minimal amount of chirp produces the most signal with only a slight loss of spectral resolution. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Fritzler S Najmudin Z Malka V Krushelnick K Marle C Walton B Wei MS Clarke RJ Dangor AE 《Physical review letters》2002,89(16):165004
Thermonuclear fusion neutrons produced by D(d,n)3He reactions have been measured from the interaction of a high-intensity laser with underdense deuterium plasmas. For an input laser energy of 62 J, more than (1.0+/-0.2)x10(6) neutrons with a mean kinetic energy of (2.5+/-0.2) MeV were detected. These neutrons were observed to have an isotropic angular emission profile. By comparing these measurements with those using a secondary solid CD2 target it was determined that neutrons are produced from direct ion heating during this interaction. 相似文献
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详细比较了磷酸二氢钾(KDP)晶体的自发拉曼散射和受激拉曼散射光谱,在受激拉曼散射(SRS)中观察到了自发拉曼散射中最强的振动模的三阶Stokes光(559.43,589.74,623.50nm),由于其他振动模的受激拉曼散射增益系数较小,其SRS光谱未观察到。另外,比较了传统生长的未退火和退火后的KDP晶体及快速生长的锥区和柱区KDP晶体的受激拉曼散射增益系数,结果表明生长方法和热退火对KDP晶体的受激拉曼散射增益系数无明显影响。 相似文献
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通过直接对减反膜外腔反馈半导体激光器进行电流调制的方法,得到了两束位相锁定且频率差在6.0-9.3GHz范围内连续可调的激光,其中6.835和9.192GHz分别对应Rb87和Cs133原子基态超精细能级之间的频率差,激光功率分别可以达到6.87mW和5.09mW. 根据减反膜外腔反馈半导体激光器的特点,通过调整外腔腔长、激光器工作温度、电流以及所加射频调制信号的功率和频率,在调制频率小于等于4.0GHz时可以将载波完全压制. 调制频率大于4.0GHz时,虽不能将载波完全压制,但由于外腔与调制频率共振时对调制的增强也得到了调制深度很高的激光,并对其中的物理机理作了分析. 通过后续滤波等方法处理以后,该拉曼光源可以广泛应用到原子的量子操控中.
关键词:
受激拉曼光
高频调制
调制增强 相似文献
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报道了“神光 Ⅱ”装置上Au大柱腔靶产生的受激Raman散射光谱。通过分析实验条件和测量结果,排除了散射光谱来自增强非相干Thomson散射的可能性,发现用丝化不稳定性与受激Raman散射的耦合能合理解释观测到的Raman光谱。考虑到丝化不稳定性与SRS的耦合,测量到的散射光谱依然能用于密度诊断,其结果与对流SRS理论的计算值相差不到10%。 相似文献
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介绍了在神光Ⅱ装置上开展的长脉冲2 ns,351 nm激光与黑腔靶相互作用的实验,报道了受激Raman散射光时间分辨谱图及能量测量的实验结果。长脉冲2 ns激光注入小腔靶(700 mm×1 250 mm)时,激光辐照缝靶产生的SRS光能量是激光与全腔靶作用产生的SRS光能量的1.3倍。在2 ns激光与不同尺寸黑腔靶作用的情况下,激光辐照小腔靶产生的SRS光能量比标准腔靶(800 mm×1 350 mm)产生的SRS光能量高1.6倍。由于激光功率密度下降,2 ns激光打靶SRS散射光要弱于短脉冲1 ns激光打靶,但持续时间稍长。实验结果表明:长脉冲2 ns激光与标准腔靶相互作用时,等离子体“堵腔效应”比较严重,标准腔靶尺寸不再合适。 相似文献
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Vladimir S. Gorelik Anna D. Kudryavtseva Nikolay V. Tcherniega 《Journal of Russian Laser Research》2008,29(6):551-557
The results of experimental studies of stimulated Raman scattering of light (SRS) excited in three-dimensional photonic crystals
— synthetic opal matrices infiltrated with Raman active media are presented. It is shown that the SRS threshold in such structures
decreases with respect to the SRS threshold in Raman active bulk materials. The influence of the photonic-band structure of
the active materials used on the SRS properties is estimated. 相似文献