共查询到17条相似文献,搜索用时 203 毫秒
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基于厄米-双曲余弦高斯光束通过无光阑限制薄透镜聚焦的解析传输公式,研究了厄米-双曲余弦高斯光束聚焦区域的光强分布,并对光束的焦移进行了分析,讨论了偏心参数对光强主极大位置的影响。结果表明:TEM11模厄米-双曲余弦高斯光束的相对焦移(绝对值)随偏心参数和菲涅尔数的减小而增大,菲涅尔数较大时相对焦移趋于零。TEM22模光束在偏心参数小于0.54时,轴外与轴上光强极大值的比值大于1,此时光强主极大在轴外,偏心参数大于0.54时则相反;在偏心参数等于0.54时比值为1,此时光束有两个主极大,偏心参数愈大光强愈集中于轴上。使用LW法和GH法得到的TEM22模光束的相对焦移(绝对值)随偏心参数和菲涅尔数的变化规律与TEM11模光束一致,但相同参数下使用这两种方法得出的具体结果不同。 相似文献
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环形光束的非线性传输及聚焦特性研究 总被引:1,自引:0,他引:1
针对用于产生光镊的环形光束,利用分步傅里叶-贝塞尔变换算法,对二维环形超高斯光束的非线性传输及聚焦过程进行了数值模拟,给出了环形光束聚焦场附近的光强分布,并分析了非线性调制对聚焦性质(包括焦面中心光强、焦面光强的横向分布、轴上光强和光束质量)的影响.研究表明,从聚焦角度来看,非线性调制中的位相调制比振幅调制对环形光束聚焦性质的影响程度要大;从非线性传输角度来看,随着非线性介质长度的增加,位相调制和振幅调制对环形光束聚焦性质各有不同程度的加剧,其中非线性作用对振幅调制的影响要比位相调制明显. 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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利用广义惠更斯-菲涅耳衍射积分法,推导出平顶高斯光束在梯度折射率介质中传输时的解析表达式,对平顶高斯光束在梯度折射率介质中的传输特性进行了分析,讨论了介质梯度折射率系数和光束阶数对传输特性的影响。研究表明,平顶高斯光束在梯度折射率介质中传输时轴上光强分布呈现周期性变化,其周期决定于介质梯度折射率系数,而与光束的阶数无关;轴上峰值处的横向光强分布受梯度折射率系数和光束阶数的影响较大,横向光强的最大值随着梯度折射率系数的增大而增大。 相似文献
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非傍轴贝塞尔-高斯光束在自由空间的传输 总被引:2,自引:2,他引:0
从瑞利-索末菲衍射积分出发,推导出任意阶非傍轴贝塞尔-高斯光束在自由空间传输的解析表达式.非傍轴贝塞尔光束和非傍轴高斯光束等的传输方程都可以作为本文一般结果的特例而得出.物理分析和数值计算表明,当高斯和贝塞尔部分的横向尺度与波长相比拟或小于波长时,应当用非傍轴方法处理. 相似文献
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By introducing a hard aperture function into a finite sum of complex Gaussian functions, an approximate analytical expression predominating the distribution of axial intensity for the flat-topped Mathieu-Gauss (FTMG) beams passing through a system with the aperture and lens separated has been derived. The focal shift and the focal switch effect of FTMG beams passing through the system is studied in detail. Numerical calculations have shown that the position of real focal plane is not coincident with the geometrical focus but is somewhat shifted toward the lens. The focal shift and focal switch of FTMG beams take place when the relative separation s/f = 1 by a suitable choice of beam parameter and truncation parameter, for example, the beam parameter is smaller than its corresponding critical value or the truncation parameter is between its two corresponding critical values. 相似文献
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The focal switch of cosine-Gaussian (CsG) beams passing through a system with the aperture and lens separated is studied analytically
and numerically. It is shown that the focal switch of CsG beams can appear not only for the apertured case, but also for the
unapertured case. The necessary condition for the focal switch is that truncation parameter α > αc and the beam parameter β > βc, αc, βc being the corresponding critical values. There exists a maximum of the relative transition height Δz
sw as α varies, and Δz
sw increases with increasing β and decreasing N
w. The normalized axial intensity minimum I
min / I
max decreases with an increase of α and β, and I
min / I
max remains unchanged as N
w varies. 相似文献
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Wang Chun-Fang Tao Xiang-Yang Nie Yi-You Zeng zhao-Yang 《Optics & Laser Technology》2007,39(2):430-434
Based on the Collins formula, we study the focal switch of spherically aberrated Laguerre–Gaussian (L–G) beams passing through an optical system with the aperture and lens separated. Our results demonstrate that the behavior of the focal switch of spherically aberrated L–G beams is generally dependent on the spherical aberration coefficient, truncation parameter, Fresnel number and mode indices. The spherical aberration affects the relative focal shift, critical position of the focal switch and the relative transition. We also illustrate that there exists a minimum in addition to a maximum in the truncation parameter. Only inside the region between the minimum and the maximum the focal switch effect can be expected. The region depends on the spherical aberration coefficient as well as the Fresnel number. 相似文献
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A detailed study of the spectrum of partially coherent beams diffracted at an astigmatic aperture lens is performed. Considerable attention is paid to the effect of astigmatism on spectral switches of polychromatic Gaussian Schell-model beams. It is shown that the spectral switch can also take place in the vicinity of intensity minimum in a geometrical focal plane for the astigmatic case, but the astigmatism of the lens and the spatial correlation of the beam affect the critical position u_c, spectral minimum S_{min}, and transition height Δ of spectral switches. 相似文献
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利用广义惠更斯-菲涅耳衍射积分公式得到了随机电磁高阶Bessel-Gaussian光束在海洋湍流中传输的交叉谱密度矩阵的一般表达式,通过数值计算主要研究了随机电磁高阶Bessel-Gaussian光束在海洋湍流中传输时其在远场输出面的统计特性的变化,包括归一化光谱强度、光谱偏振度、两点的光谱相干度等.数值模拟结果显示海洋湍流能够对随机电磁高阶Bessel-Gaussian光束的归一化光谱强度分布产生影响,随着传输距离的增加,零阶Bessel-Gaussian光束中心出现凹陷,高阶Bessel-Gaussian光束中心会变平坦继而又凹陷下去,不管零阶还是高阶,当传输距离增加到足够远,光强分布都会演变成最终的类高斯分布.x轴上各点的偏振度改变与相干长度δ_(xx),δ_(yy)以及海洋湍流参数有关.x轴上任意一点和原点这两点的光谱相干度也随x的增加而呈振荡变化,并且海洋的均方温度耗散率χT对光谱相干度有影响. 相似文献
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Focal shift and focal switch of Bessel–Gaussian beams passing through a lens system with or without aperture 总被引:1,自引:1,他引:0
The focal shift and focal switch of Bessel–Gaussian (B–G) beams passing through a lens system with or without aperture is studied in detail. For the unapertured case, the necessary condition for the focal switch and the expression for the amplitude of the focal switch are derived. It is shown that if the truncation parameter δδc or beam parameter ββc (δc, βc are the corresponding critical values), there exits only one axial intensity maximum, and the focusing without focal shift can be achieved for u/f=1 (u is the separation between the aperture and lens, f is the focal length of the lens); if δ>δc and β>βc, there exist two axial intensity maxima, and the focal switch can take place at the turning point u/f=1 for both apertured and unapertured cases. The dependence of the amplitude of focal switch and normalized axial intensity minimum on the truncation parameter, beam parameter and Fresnel number is also studied. 相似文献
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Propagation of modified Bessel-Gaussian beams in turbulence 总被引:2,自引:0,他引:2
We investigate the propagation characteristics of modified Bessel-Gaussian beams traveling in a turbulent atmosphere. The source beam formulation comprises a Gaussian exponential and the summation of modified Bessel functions. Based on an extended Huygens–Fresnel principle, the receiver plane intensity is formulated and solved down to a double integral stage. Source beam illustrations show that modified Bessel-Gaussian beams, except the lowest order case, will have well-like shapes. Modified Bessel-Gaussian beams with summations will experience lobe slicing and will display more or less the same profile regardless of order content. After propagating in turbulent atmosphere, it is observed that a modified Bessel-Gaussian beam will transform into a Bessel-Gaussian beam. Furthermore it is seen that modified Bessel-Gaussian beams with different Bessel function combinations, but possessing nearly the same profile, will differentiate during propagation. Increasing turbulence strength is found to accelerate the beam transformation toward the eventual Gaussian shape. 相似文献