共查询到17条相似文献,搜索用时 343 毫秒
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基于广义惠更斯-菲涅耳原理,并采用Rytov相位结构函数二次近似,推导出了部分相干厄米-高斯(H-G)光束通过大气湍流传输的光谱相干度公式,研究了湍流对光束的空间相干特性的影响.研究表明,部分相干H-G光束通过大气湍流传输其光谱相干度会出现振荡和相位奇异现象,但随着湍流的增强,振荡减弱,直至振荡和相位奇异现象消失,这一特性与高斯-谢尔模型光束的差异很大.光束的相干参数越小,光束空间相干性受湍流的影响也越小.此外,还研究了光谱相干度二阶矩宽度与光谱强度二阶矩宽度间的关系,得到一些有意义的结果,并给出了合理的
关键词:
部分相干厄米-高斯光束
大气湍流
光谱相干度
二阶矩宽度 相似文献
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对部分空间和部分光谱相干2维高斯-谢尔模型脉冲光束在自由空间传输的光谱和时间特性做了详细的数值研究。结果表明,部分空间和部分光谱相干高斯-谢尔模型脉冲光束在自由空间传输中发生了光谱移动,光谱移动与场点位置、空间相关长度和时间相干长度有关。在轴上,光谱出现蓝移,相对光谱移动随传输距离的增加而增大,随空间相关长度和时间相干长度的增加而减小,并逐渐趋于一定值。在轴外,光谱出现蓝移和红移,并与空间相关长度和时间相干长度有关。脉冲时间波形不变,对所得主要结果做了物理解释。 相似文献
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对啁啾高斯脉冲光束在色散介质中的时间和光谱特性作了研究.给出了远场光谱蓝移和脉冲展宽的解析式.结果表明:通过选择适当的啁啾参量,啁啾高斯脉冲光束沿轴上传输色散长度时,脉冲可恢复到初始值.随啁啾参量增加,谱线宽度展宽,轴上光谱蓝移增加,在远场蓝移趋于一渐近值.随啁啾参量增加,离轴光谱红移增加. 相似文献
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超短脉冲贝塞尔-高斯光束在自由空间的传输特性 总被引:3,自引:0,他引:3
使用复解析信号法研究了束宽与频率无关的超短脉冲贝塞尔-高斯光束在自由空间的传输特性。研究表明:在无衍射长度内,超短脉冲贝塞尔-高斯光束的横向光强分布几乎不变并集中在传输轴附近,轴上脉冲随传输距离增加而展宽。在无衍射长度外,横向光强分布显著扩展。随传输距离增加,轴上光谱蓝移先增加,达到极大值后逐渐减小,最后在远场趋于一渐近值。对单周期的超短脉冲贝塞尔-高斯光束的轴上光谱蓝移先增加,达到极大值0.50 fs-1。然后逐渐减小,在远场蓝移趋于渐近值0.16 fs-1。 相似文献
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使用复解析信号法,研究了衍射长度与频率无关的超短脉冲贝塞耳-高斯光束在自由空间中的传输,推导出了解析表达式并进行了理论和计算分析.结果表明:在无衍射长度内,等衍射长度超短脉冲贝塞耳.高斯光束的横向光强分布扩展很小.在无衍射长度之外,横向光强分布有显著扩展.但是,在无衍射长度内轴上脉冲波形仍有展宽.随传输距离增加轴上蓝移单调增加逐渐达到一渐近值.随横向距离增加轴外光谱移动由蓝移变为红移. 相似文献
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部分相干厄米-高斯列阵光束通过湍流大气传输的方向性 总被引:1,自引:0,他引:1
推导出了部分相干厄米-高斯(H-G)列阵光束通过湍流大气传输的二阶矩束宽和远场发散角的解析公式。采用远场发散角作为光束方向性的评价参数,研究了部分相干H-G列阵光束通过湍流大气传输的方向性。研究表明:在一定条件下,部分相干H-G列阵光束与对应的高斯光束不论在自由空间还是湍流大气中均具有相同的方向性。此外,进一步研究发现,在自由空间中,由远场发散角和归一化远场平均光强分布所表征的部分相干H-G列阵光束的方向性是不一致的,但湍流可以使得两种描述相一致。这一结论与高斯-谢尔模型(GSM)列阵光束的相关结论存在差异。在自由空间中,与高斯光束具有相同远场发散角的非相干合成的GSM列阵光束与对应的高斯光束具有相同的归一化远场光强分布。 相似文献
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Xiaoling Ji 《Optics Communications》2008,281(13):3407-3413
The influence of turbulence on the spectrum of diffracted chirped Gaussian pulsed beams is studied in detail. By using the quadratic approximation of the Rytov’s phase structure function and the finite expansion of the aperture function, the analytical expression for the spectrum of diffracted chirped Gaussian pulsed beams propagating through atmospheric turbulence is derived. It is shown that in free space there exist the on-axis and off-axis multi-spectral switch for diffracted chirped Gaussian pulsed beams. However, the turbulence results in a decrease of the spectral transition height, and the spectral switch even disappears when the turbulence is strong enough, which is very different from the behavior of undiffracted chirped Gaussian pulsed beams. Specially, with increasing the strength of turbulence, the higher-order spectral switch disappears firstly for on-axis case, while the lower-order spectral switch disappears firstly for off-axis case. In free space the on-axis spectrum is blue-shifted after a certain propagation distance, but the on-axis spectrum is red-shifted after a shorter propagation distance when the turbulence is strong enough. The spectral transition height increases with increasing the chirp parameter and decreasing the pulse duration, and the odd number order position without spectral shift is independent of the chirp parameter and pulse duration. 相似文献
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多色高斯-谢尔模型光束通过球差透镜的光谱变化 总被引:1,自引:1,他引:0
基于部分相干光的传输方程研究了多色高斯一谢尔模型光束通过球差透镜的光谱变化。结果表明,多色高斯一谢尔模型光束通过球羞透镜后的轴上光谱与空间相关参量β,球差系数C1,源光谱谱宽σ0,位置z有关。着重分析了球差对轴上光谱的影响,将所得的结果与无像差的理想情况作了比较。当无球差时,轴上光谱仅有蓝移,而有球差时,轴上光谱存在蓝移或红移,并会出现光谱分裂现象。在某些特定位置处,轴上光谱分裂为等高双峰,并有跃变出现。而且,球差对光谱的影响随空间相关性增加而变得明显。当空间相关参量减小到某一值时,光谱分裂消失。 相似文献
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The temporal and spectral properties of ultrashort pulsed Laguerre-Gaussian (LG) beams propagating in dispersive media are studied both theoretically and numerically. It is shown that the on-axis pulse broadens with increasing propagation distance and the on-axis spectrum is blueshifted. For the off-axis spectrum the blueshifts decrease and then the spectrum becomes redshifted as the radial distance increases. The propagation of ultrashort pulsed LG beams in free space and of ultrashort pulsed Gaussian beams can be regarded as special cases of our results, and some interesting properties are discussed. 相似文献
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Changes in the spectrum of twist anisotropic Gaussian Schell-model beams propagating through turbulent atmosphere 总被引:1,自引:0,他引:1
Based on the extended Huygens-Fresnel principle, the spectrum of twist anisotropic Gaussian Schell-model (TAGSM) beams propagating through turbulent atmosphere is derived analytically by using the partially coherent complex curvature tensor. The relative spectral shift of TAGSM beams propagating through turbulent atmosphere is closely related with the strength of atmospheric turbulence, the beam’s parameter and the radial coordinate. The on-axis spectral shift of TAGSM beams propagating through turbulent atmosphere changes from blue shift to red shift with the increasing of the propagation distance z, and at a certain propagation distance z, there exists a rapid transition of the spectrum at the critical position rc. 相似文献
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The chemical shift anisotropy of a nuclear spin system in a strong magnetic field can be comparable to the strength of the rf pulse (weak pulse condition). In this case, the commonly used assumption that the chemical shift interaction Hamiltonian in the duration of a rf pulse can be neglected is no longer effective. The rf response characteristics of a spin-1/2 system under a weak pulse condition is studied in detail. The relationships between the distortion of the chemical shift powder spectrum and the relative rf field amplitude under various conditions are given. The suppression of sidebands of a MAS spectrum is analysed as an example of solid multiple pulse experiments. The experimental results are in good agreement with computer simulations. 相似文献
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基于激光诱导击穿光谱技术, 利用Nd:YAG脉冲激光激发Al2O3 (含量为99%)陶瓷片产生等离子体, 获得了AlO自由基B2∑+–X2∑+跃迁的33条发射谱线. 就AlO自由基光谱的时间演化规律和激光能量对谱线的影响规律进行了研究与分析. 结果表明, AlO自由基光谱出现在Al原子和Al离子光谱之后, 且持续时间较长. 当激光的脉冲能量由10 mJ起不断增加时, AlO自由基光谱强度逐渐减小, 且最大值出现时间随激光能量的增加而后移. 在此基础上, 进行了陶瓷等离子体在空气和氩气环境下的对比试验, 发现从Al2O3陶瓷片中激发所产生的AlO自由基必须有空气中O2参与反应.
关键词:
激光诱导击穿光谱
AlO自由基
B2∑+–X2∑+跃迁光谱')" href="#">B2∑+–X2∑+跃迁光谱 相似文献