共查询到19条相似文献,搜索用时 140 毫秒
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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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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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研究了湍流对离轴列阵高斯光束相干与非相干合成的影响.推导出了相干合成光束的传输方程.采用二阶矩束宽、桶中功率和参数β作为光束质量评价参数比较了离轴列阵高斯光束通过湍流大气的相干与非相干合成,并对主要结果给予了合理的物理解释.研究表明:一方面,不论是相干合成还是非相干合成,湍流都使得合成光束扩展、峰值光强下降,并且子光束数越多,合成光束受湍流影响就越小.另一方面,非相干合成光束较相干合成光束受到湍流的影响要小.
关键词:
相干与非相干合成
湍流大气
离轴列阵高斯光束 相似文献
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推导了多色部分相干偏心光束在non-Kolmogorov 湍流中传输的总光强、轴上光谱、相干度的解析表达式, 研究了光束偏心参数β 、湍流广义指数α和源光谱带宽Ω对激光传输特性的影响. 研究表明: β越大, 则光束重心偏离传输轴越远, 相干度的不对称性越明显, 但是, β对轴上光谱几乎没有影响; 湍流广义指数α对总光强、 轴上光谱和相干长度的影响是非单调的, 当α=3.1时, 湍流对光束传输特性的影响最大. 值得指出的是: 在某些传输距离处, 不同α对应的轴上光谱位移量相同; 在某些传输距离处, 轴上光谱位移量为零, 且该传输距离与Ω无关, 但湍流使得该传输距离缩短. 所得结论对多色部分相干偏心光束在 湍流大气中传输的相关应用具有重要意义.
关键词:
non-Kolmogorov湍流
多色部分相干偏心光束
光谱强度
相干度 相似文献
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利用矢量瑞利-索末菲衍射积分公式,推导出了非傍轴部分空间相干部分光谱相干双曲余弦-高斯(ChG)脉冲电磁光束在自由空间传输时交叉谱密度矩阵的远场解析公式,并用来表示脉冲电磁光束的光谱密度(光强)和偏振度。结果表明,对非傍轴远场部分空间相干部分光谱相干ChG脉冲电磁光束,其非傍轴性主要由参数f, f决定,而离心参数、脉冲宽度和时间相干长度影响其非傍轴行为。非傍轴部分空间相干部分光谱相干高斯-谢尔模型脉冲电磁光束的远场传输可作为特例处理。 相似文献
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Xiaoqing Li 《Optics Communications》2009,282(1):7-1239
The influence of atmospheric turbulence on the propagation of superimposed partially coherent Hermite-Gaussian (H-G) beams is studied in detail. The closed-form propagation equation of superimposed partially coherent H-G beams through atmospheric turbulence is derived. It is shown that the turbulence accelerates the evolution of three stages which superimposed partially coherent H-G beams undergo. The turbulence results in a beam spreading and a decrease of the maximum intensity. However, the larger the beam number M, the beam order m, the separate distance xd, and the smaller the beam correlation length σ0 are, the less the power focusability of superimposed partially coherent H-G beams is affected by the turbulence. Specially, superimposed partially coherent H-G beams are less sensitive to turbulence than superimposed fully ones, and than partially coherent H-G beams if the beam power focusability and the maximum intensity are taken as beam criterions. However, the maximum intensity of superimposed partially coherent H-G beams is less sensitive or more sensitive to turbulence than that of superimposed Gaussian Schell-model (GSM) beams depending on σ0. 相似文献
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基于广义惠更斯-菲涅尔原理,并采用将部分相干双曲余弦高斯光束用厄米-高斯光束的非相干叠加表示的方法,研究了部分相干双曲余弦高斯光束通过湍流大气的光束扩展问题,推导出了部分相干双曲余弦高斯光束通过湍流大气均方根束宽的解析表达式.研究表明,部分相干双曲余弦高斯光束的扩展随着湍流大气的折射率结构常数C2n和光束离心参数δ的增大而加剧.但是,随着δ的增大,部分相干双曲余弦高斯光束受到湍流的影响减小.
关键词:
部分相干双曲余弦高斯光束
湍流大气
光束扩展 相似文献
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推导出部分相干厄米-双曲正弦-高斯(H-ShG)光束通过湍流大气的平均光强和角扩展的解析表示式,并用以研究了部分相干H-ShG光束在湍流中的平均光强分布演化和角扩展. 结果表明,折射率结构常数C2n的增加和空间相关长度σ0的减小都会加速演化过程. 引入相对角扩展来定量描述光束抗拒湍流的能力. 空间相关长度σ0,束腰宽度w0和双曲
关键词:
平均光强分布演化
角扩展
湍流大气
部分相干厄米-双曲正弦-高斯(H-ShG)光束 相似文献
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高功率光纤激光部分相干合成的可行性及效果分析 总被引:2,自引:0,他引:2
提出部分相干合成的概念,论证了谱线宽度和偏振特性并不是影响高功率光纤激光部分相干合成的瓶颈.与完全相干合成的理想情形相比,随着光束线宽的增大,部分相干合成光束的远场光斑图样基本保持不变,但峰值强度和斯特尔(Strehl)比随之减小,光斑能量越来越分散.利用数值计算的方法对部分相干合成与非相干合成光束的远场效果进行了比较分析.计算结果表明,尽管线宽的存在降低了部分相干合成的效果,但与非相干合成相比,部分相干合成的光束仍具有较大优势. 相似文献
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The closed-form expression for the mean-squared width of apertured partially coherent beams propagating through turbulent media is derived by using the integral transform technique. The influence of turbulence on the spreading of apertured partially coherent beams is studied quantitatively by examining the relative mean-squared width, which is defined as the ratio of the mean-squared width of an apertured partially coherent beam in turbulence to the mean-squared width of the same beam in free space. On the other hand, the range of turbulence-independent propagation, also a reasonable measure of the resistance of a beam to turbulence, is obtained by examining the mean-squared width. It is shown that the spreading of apertured partially coherent beams is less affected by turbulence with smaller truncation parameter δ and coherence parameter α than with larger δ and α. In addition, the influence of turbulence on the spreading of apertured partially coherent beams increases first and then decreases due to increasing waist width w0. The results obtained are explained physically. 相似文献
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Based on the generalized Huygens–Fresnel diffraction integral and the theory of partially coherent light, the axial intensity distribution and the focal shifts of focused partially coherent conical Bessel–Gauss beams are investigated. The dependence of the maximum on-axis intensity and the associated focal shift on the Fresnel number and the coherence parameter are examined and illustrated numerically. The results related to the J
0-correlated beams and the fully coherent Bessel–Gauss beams are obtained as particular cases of this study. 相似文献
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采用积分变换的技巧,推导出了径向分布高斯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,并详细研究了大气湍流对光束扩展和方向性的影响.研究表明,相干合成情况下,子光束数N越小、径向分布半径r0越大,列阵光束扩展受湍流影响越小.相干较非相干合成时列阵光束的扩展小,但非相干合成时列阵光束扩展受湍流的影响比相干合成时的小.特别地,N足够小或r0足够大时,相干与非相干合成列阵光束的远场束宽相等.另一方面,还给出了相干和非相干合成径向分布高斯列阵
关键词:
径向分布高斯列阵光束
大气湍流
相干和非相干合成
二阶矩束宽 相似文献
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Propagation of the off-axis superposition of partially coherent beams through atmospheric turbulence 下载免费PDF全文
The propagation properties of the off-axis superposition of
partially coherent beams through atmospheric turbulence and their
beam quality in terms of the mean-squared beam width w(z) and the
power in the bucket (PIB) are studied in detail, where the effects
of partial coherence, off-axis beam superposition and atmospheric
turbulence are considered. The analytical expressions for the
intensity, the beam width and the PIB are derived, and illustrative
examples are given numerically. It is shown that the maximum
intensity Imax and the PIB decrease and w(z) increases as
the refraction index structure constant Cn2 increases.
Therefore, the turbulence results in a degradation of the beam
quality. However, the resulting partially coherent beam with a
smaller value of spatial correlation parameter γ and larger
values of separate distance xd and beam number M is less
affected by the turbulence than that with a larger value of γ
and smaller values of xd and M. The main results obtained
in this paper are explained physically. 相似文献
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Based on the extended Huygens–Fresnel principle, the closed-form propagation equation of partially coherent Sinh-Gaussian (ShG) beams through the turbulent atmosphere has been derived by using the quadratic approximation of the Rytov's phase structure function. The influence of turbulence on propagation properties of partially coherent ShG beams and their beam quality in the far field are studied both analytically and numerical. The fully coherent ShG beam has been treated as a special case of the partially coherent ShG beam when the degree of spatial coherence α=∞. It is shown that in comparison with the free-space propagation the turbulence accelerates the evolution of three stages that partially coherent ShG beams undergo. The smaller α is, the less partially coherent ShG beams are affected by the turbulence. In particular, we find that the β parameter decreases as the decentered parameter δ increases, but the dependence of the Strehl ratio on δ is not monotonous. There exists an optimal δopt, the influence of turbulence on the maximum intensity of the corresponding partially coherent ShG beam with δopt is the smallest. Therefore, a suitable choice of δ may reduce the influence of turbulence on the beam quality in the far field in practice. 相似文献