共查询到20条相似文献,搜索用时 187 毫秒
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以亚当姆预测 校正系统数值计算方法为基础,在同时考虑光束通过克尔介质后的相位和光束线型变化的情况下,利用惠更斯 菲涅尔衍射积分公式,对高斯光束通过克尔介质后的近场和远场的横向光强分布进行了研究.结果表明:当高斯光束通过“薄”介质的出射面时,不仅仅相位发生了变化,而且光强线型分布也不再呈理想的高斯分布,而是有一系列丝状的近高斯分布.光束通过克尔介质后,无论是在近场还是远场,其光束总能量分布都被发散了.结果同时表明:光束通过正克尔介质后的远场光强分布主要集中在中心附近,并逐渐向边缘减弱,而光束通过负克尔介质后远场光束能量主要集中在边缘. 相似文献
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为了研究高功率激光系统中划痕型缺陷对光场质量的影响,采用分步傅里叶算法对非线性近轴波动方程进行求解,模拟分析了不同划痕参数(长度、宽度、深度)下,元件内部、光束近场、元件后传输光场以及光束远场的光强分布情况。数值模拟结果表明:随着划痕长度、宽度或深度的增加,元件内部以及元件后传输光场的峰值强度和对比度均会相应增强;光束近场的光强对比度也会略微增大;对于光束远场的强度分布,与划痕宽度方向所对应的频谱能量会不断增强。该项研究工作可以为划痕检验标准的制定提供一定的定量分析依据。 相似文献
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基于光传输理论,获得了弱调制情况下光学元件"缺陷"分布功率谱密度 (power spectral density, PSD)与光束近场强度分布PSD之间的定量关系;通过数值模拟的方法,针对高功率固体激光装置的基本单元(线性介质、非线性介质以及空间滤波器)对获得的理论关系进行了具体的验证和讨论.研究结果表明,弱调制下,只存在振幅型或位相型"缺陷"分布时,光学元件"缺陷"分布PSD与光束近场强度分布PSD通过近场强度分布PSD的系统传输因子联系,传输因子与系统的构型和运行状态有关.研究结果为光学元件"缺陷"分布指标的获得提供了理论基础,对高功率固体激光装置负载能力的提升起到了一定的指导作用.
关键词:
缺陷分布
功率谱密度
光学元件
光束质量 相似文献
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建立了封闭竖直管道热耦合效应物理模型,采用流固耦合方法,数值模拟了封闭管道中介质气体、光学玻璃之间的热相互作用造成流场分布的变化,研究了热耦合作用对近场波前相差和远场光束质量的影响。数值模拟结果表明,光束质量可以由封闭管道内介质气体温度分布来决定,气体在管道内流动改变温度分布,使得相差分布不断变化,造成远场光束质量的振荡起伏;光学镜与介质气体热相互作用对流场分布有较大影响,尤其是竖直管道底部的光学镜对激光束远场光束质量影响明显。热耦合效应放大了光束质量的变化:当介质模型中光束质量变差,热耦合模型中热耦合效应使光束质量变得更差;当介质模型中光束质量变好,耦合模型中的热耦合作用使光束质量变得更好,即光束质量随着流场分布的变化而振荡。 相似文献
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The propagation characteristics of a scalar Gaussian beam in a homogeneous anisotropic medium are considered. The medium is described by a generic wave-number profile wherein the field is formulated by a Gaussian plane-wave distribution and the propagation is obtained by saddle-point asymptotics to extract the Gaussian beam phenomenology in the anisotropic environment. The resultant field is parameterized in terms of e.g., the spatial evolution of the Gaussian beam's curvature, beam width, which are mapped to local geometrical properties of the generic wave-number profile. 相似文献
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当高功率激光通过Kerr非线性介质传输时,Kerr效应会严重影响激光的传输特性.实际应用中常遇到像散光束.迄今为止,像散光束传输特性的研究大都局限于在线性介质中的传输,而在非线性介质中传输的研究较少,且还未涉及像散激光束通过含光学系统的Kerr非线性介质传输变换的研究.本文主要研究Kerr效应对聚焦光束像散特性和焦移特性的影响,以及聚焦像散高斯光束的自聚焦焦距和光束焦点调控.在光束扩展情况下,推导出了聚焦像散高斯光束在Kerr非线性介质中传输的束宽、束腰位置和焦移的解析公式,研究表明:在自聚焦介质中,随着自聚焦作用增强(如光束功率增强),光束像散越强,但焦移越小;在自散焦介质中,随着自散焦作用增强(如光束功率增强),光束像散越弱,但焦移越大.另一方面,在光束自聚焦情况下,推导出了自聚焦焦距的解析公式,研究表明利用光束像散可以调控光束焦点个数. 相似文献
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Propagation of optical vortex solitons due to the Gouy phase in strongly nonlocal nonlinear media
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In this paper,we present a study on the propagation of the symmetrical optical vortices formed by two collinear Laguerre-Gauss solitons in strongly nonlocal nonlinear media.The optical vortices,which move along the beam axis as the light propagates,result in a rotation of the beam’s transverse profile.This physical reason of the rotation is the Gouy phase acquired by the component beams. 相似文献
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以高斯光束为例,研究了非线性介质表面振幅调制型缺陷对光场的调制。基于广义惠更斯-菲涅尔衍射积分并采用泰勒级数展开方法,建立了高斯光束经过表面存在缺陷的非线性介质后的传输模型,得到了受缺陷调制光束经非线性介质后的光强分布解析式,研究了缺陷尺寸和光束在非线性介质中产生的附加相移大小对光强分布的影响,结果表明介质表面的缺陷尺寸越大,介质内产生的附加相移越大,光场受到的调制越严重。分别考虑了非线性折射率为正值和为负值的情况,研究发现相应的折射率值导致光束发生会聚或发散现象,并由于缺陷调制的作用,在光束传输过程中始终存在一光强极值点,且随着附加相移绝对值的增大光强极值点的峰值也随之增强。 相似文献
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We report the first successful attempt to generate ultrashort (1-10 ps) relativistic electron bunches characterized by a ramped longitudinal current profile that rises linearly from head to tail and then falls sharply to zero. Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free-electron lasers as a means of reducing asymmetry in microbunching due to slippage. The scheme used to generate the ramped bunches employs an anisochronous dogleg beam line with nonlinear correction elements to compress a beam having an initial positive time-energy chirp. The beam current profile is measured using a deflecting mode cavity, and a pseudoreconstruction of the beam's longitudinal phase space distribution is obtained by using this diagnostic with a residual horizontal dispersion after the dogleg. 相似文献
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利用菲涅尔-基尔霍夫衍射积分公式,对发散和会聚高斯光束通过薄非线性介质时形成的远场衍射图样进行了研究。模拟计算结果表明:当发散高斯光束通过自散焦介质或会聚高斯光束通过自聚焦介质时,远场均会出现中央较暗、向外围逐渐增强、分布尺度较大的粗衍射环;当发散高斯光束通过自聚焦介质或会聚高斯光束通过自散焦介质时,远场均会出现中心强度最大、向外围逐渐减弱、分布尺度较小的细衍射环。不同远场衍射图样归根结底是入射高斯光束因介质折射率变化造成的空间自相位调制及其波前曲率共同作用的结果。 相似文献
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Electron beam modeling and analyses of the electric field distribution and space charge effect
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Yueling Jiang 《中国物理 B》2022,31(5):54103-054103
In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam's cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed. 相似文献
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In this paper, frequency-doubled Nd:YAG laser's phase conjugation has been investigated experimentally using resonant degenerate four-wave mixing (DFWM). The iodine solution was used as resonant medium. In this way, the energy of the DFWM phase conjugation beam arrived at 43μJ/pulse while the total pump beam's energy reached 8mJ/pulse. The relation between the pulse energy of the DFWM phase conjugation beam and that of the pump beam was investigated. We also measured the optical field distributions of pump beam and DFWM phase conjugation beam, from which it can be noticed that the DFWM phase conjugation can improve the laser beam quality. At the same time, we observed the influence of the pump beam's disturbance on the DFWM signal. 相似文献