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1.
Helico-conical beam is attractive for its phase front is nonseparable helical and conical phase function, which produces a spiral intensity distribution occurs at the focal plane. In this letter, the focal properties of cosh-Gaussian beam with helico-conical wavefront were investigated to show that helico-conical phase front does not always produce spiral intensity distribution. On increasing decentered parameters in cosh parts of the beams, the spiral focal pattern evolves into multiple intensity peaks with center main strongest peak. Under condition of higher decentered parameters, the focal spiral curve disappears. In addition, the topological charge also affects the focal pattern considerably. 相似文献
2.
Focus shape plays an important role in many optical systems, and has attracted much attention. In this article, the focusing properties of hyperbolic-cosine-Gaussian (cosh-Gaussian) beams through a helical axicon were investigated theoretically. Results show that intensity distribution in focal region can be altered considerably by the decentered parameter of cosh-Gaussian beam, axicon parameter and topological charge of the helical axicon. Many novel focal pattern may occur, including annular focus, rectangular focal shape, multiple-peak focal pattern. And in order to show the possible applications of these alter focal pattern, some optical gradient force distributions were also calculated and illuminated. 相似文献
3.
Density transition based self-focusing of cosh-Gaussian laser beam in plasma with linear absorption has been studied. The field distribution in the plasma is expressed in terms of beam width parameter, decentered parameter, and linear absorption coefficient. The differential equation for the beam width parameter is solved by following Wentzel—Kramers—Brillouin (WKB) and paraxial approximation through parabolic wave equation approach. The behaviour of beam width parameter with dimensionless distance of propagation is studied at optimum values of plasma density, decentered parameter and with different absorption levels in the medium. The results reveal that these parameters can affect the self-focusing significantly. 相似文献
4.
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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部分相干双曲余弦-高斯光束的传输特性和空间整形 总被引:1,自引:0,他引:1
通过加入高斯项的空间相干度,引入部分相干双曲余弦-高斯(ChG)光束,推导出部分相干ChG光束通过近轴ABCD光学系统传输的解析表达式,并用以研究其传输特性和空间整形。结果表明,部分相干ChG光束的光强分布不能保持传输不变性,其光强分布不仅与传输距离和离心参数有关,而且还与空间相干参数有关。在传输距离固定时,适当改变部分相干ChG 光束的离心参数和空间相干参数,可实现光束的空间整形。光束质量因子随空间相干性的增大和离心参数的减小而减小。高斯-谢尔模型光束和完全相干ChG光束可作为部分相干ChG光束的特例处理。 相似文献
7.
The pure phase plate was introduced to alter the half-space phase value of the incident linearly polarized hyperolic-cosine-Gaussian (cosh-Gaussian) beams with sine-azimuthal variation wavefront, and focusing properties of the cosh-Gaussian beams by half space phase plate were investigated in detail. Simulation results show that focal pattern can be altered very considerably by the phase plate under condition of different beam parameters, numerical aperture, and phase parameter that indicates the phase change frequency on increasing azimuthal angle. Symmetry of the whole focal pattern can be altered remarkably, polysymmetrical focal patterns evolve into nonsymmetrical focal patterns. And some novel focal shape may appear, including cross-shape, multiple-peak focal pattern, multiple intensity lines, wheel focal pattern, swallowtail focal pattern, and dark hollow focal spots. 相似文献
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Effect of critical beam radius on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive nonlinearity forms the main core of present work. To investigate propagation dynamics of cosh-Gaussian laser beams in collisionless magnetized plasma, well established parabolic equation approach under WKB and paraxial approximations is employed. Our study is crucially pivoted on the concept of critical curve and subsequent determination of numerical interval for decentered parameter to sustain the competition between diffraction and self-focusing during the propagation of laser beam. Additionally, in the present study an interesting feature in the self-focusing region of the critical curve has been attempted for different values of decentered parameter. 相似文献
10.
T. U. Urunkar S. D. Patil A. T. Valkunde B. D. Vhanmore K. M. Gavade M. V. Takale 《理论物理通讯》2018,70(2):220-224
Effect of critical beam radius on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive nonlinearity forms the main core of present work. To investigate propagation dynamics of cosh-Gaussian laser beams in collisionless magnetized plasma, well established parabolic equation approach under WKB and paraxial approximations is employed. Our study is crucially pivoted on the concept of critical curve and subsequent determination of numerical interval for decentered parameter to sustain the competition between diffraction and self-focusing during the propagation of laser beam. Additionally, in the present study an interesting feature in the self-focusing region of the critical curve has been attempted for different values of decentered parameter. 相似文献
11.
Half-space amplitude modulation was introduced into the linearly polarized cosh-Gaussian beams with sine-azimuthal variation wavefront, and corresponding tunable focal patterns were investigated in detail. Simulation results show that focal pattern can be changed remarkably by the amplitude modulation. And under condition of different beam parameters and phase parameter that indicates the sine-azimuthal variation wavefront, the focal pattern evolution also differs considerably. Some novel focal shape may appear, including cross-shape, multiple-peak focal pattern, multiple intensity lines, wheel focal pattern, bell shape, and swallowtail focal spots. Symmetry of the whole focal pattern can be altered remarkably, the whole focal pattern evolves into uniaxial symmetry about perpendicular axes for odd and even phase parameter, respectively. 相似文献
12.
Focus evolution of linearly polarized Lorentz beam with sine-azimuthal variation wavefront induced by one on-axis optical vortex was investigated theoretically in this article. Calculation results show that the focal pattern can be altered considerably by the charge number of on-axis optical vortex under condition of certain beam parameters and phase parameter that indicates the sine phase change frequency on increasing azimuthal angle. And the focal evolution principle differs remarkably for different beam parameters and the phase parameter. In focus evolution process, some novel focal patterns appear, including annular focal pattern, two-peak focal pattern, intensity lines, hexagon containing two peaks, swallowtail shape, multipede shape, and complex focal pattern. Introduction of optical vortex adds one controllable parameter to alter focal pattern, which may extend application of Lorentz beam in some focusing systems. 相似文献
13.
The analytical expressions for the spectral degree of coherence and spectral intensity of spatially and spectrally partially coherent cosh-Gaussian pulsed (ChGP) beams propagating in free space are derived. It is shown that the spectral degree of coherence and spectral intensity of spatially and spectrally partially coherent ChGP beams depend on the spatial correlation parameter, decentered parameter and temporal coherence length. Depending on the decentered parameter, the effective width of the spectral degree of coherence can be larger than, smaller than or equal to that of the spectral intensity. The results are illustrated by numerical examples. 相似文献
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Dongbing Liu 《Optics Communications》2010,283(3):379-385
The analytical expression for the spectrum of spatially and spectrally partially coherent cosh-Gaussian pulsed (ChGP) beams focused by an aperture lens is derived and used to study their spectral properties at the focal plane and on the axis. The effect of the truncation parameter, spatial correlation parameter, decentered parameter and temporal coherence length on the spectral shifts and spectral switches of spatially and spectrally partially coherent ChGP beams is stressed. The results are illustrated numerically and interpreted physically. 相似文献
16.
Xiumin Gao Zhuo Li Jian Wang Lingling Sun Songlin Zhuang 《Optics and Lasers in Engineering》2010,48(7-8):766-773
Gradient force plays an important role in optical tweezers technique. In this paper, the tunable gradient force in focal plane of the hyperbolic-cosine–Gaussian (ChG) beam is investigated numerically. The ChG beam contains one spiral vortex and one non-spiral vortex. Simulation results show that the gradient force distribution can be altered considerably by decentered parameters of ChG beam, topological number of the spiral vortex, and vortex parameter of the non-spiral vortex. Many novel gradient force patterns can occur, which means corresponding optical traps may come into being, including ring optical trap, multiple-point trap pattern, line optical trap, rectangle trap pattern, and rhombus trap pattern. In addition, force pattern evolution principle may also differ significantly. 相似文献
17.
矢量非傍轴双曲余弦-高斯光束 总被引:3,自引:3,他引:0
引入了矢量非傍轴双曲余弦-高斯(ChG)光束概念。使用矢量瑞利-索末菲衍射积分公式推导出了矢量非傍轴ChG光束在自由空间传输的解析公式。矢量非傍轴ChG光束轴上和远场的解析式以及傍轴结果作为一般传输公式的特例给出。研究表明,对矢量非傍轴ChG光束,其非傍轴性主要由f参数决定,但偏心参数会影响其横向光强剖面形状和非傍轴行为。 相似文献
18.
Radially polarized beam has gained much interest recently due to its properties and applications. In this article, the focusing properties of radially polarized beam with radial cosine phase wavefront are investigated theoretically. Results show that when the radially polarized beam with radial cosine wavefront phase is focused, the focal pattern differs considerably with frequency parameter in the cosine function term. In the high numerical aperture focusing system, focal shift occurs, and novel focal patterns evolve considerably, for instance, from only one peak to two or multiple overlapping peaks. In addition, peak intensity ratio of radially polarized component to longitudinal polarized component in the focal region fluctuates smoothly for low-frequency parameter, then drops sharply, and comes back remarkably with increasing frequency parameter. Simultaneously focal shift increases slowly, and then decreases, suddenly, focal shift sign changes that results from focal switch phenomenon, and then fluctuates. 相似文献
19.
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
20.
Xiumin Gao Qi Wang Qiufang Zhan Maojin Yun Hanming Guo Songlin Zhuang 《Optical and Quantum Electronics》2011,42(6-7):367-380
Intensity distribution in focal region plays an important role in many optical systems. In this paper, the focal patterns of higher order hyperbolic-cosine-Gaussian (HOCG) beam in focal plane were investigated. The HOCG beam contains one spiral optical vortex on its optical axis. Results show that the focal pattern can be altered considerably by beam order of the incident HOCG beam, and some novel focal patterns may occur, including foursquare focal pattern, cross-shaped dark focal focus, foursquare intensity peaks chain, and multiple intensity peaks array. Focal pattern evolution principle on increasing beam order also differs remarkably under condition of different topological charge of the optical vortex and displacement parameter associated with the cosh parts. And like topological charge and displacement parameter, the beam order and numerical aperture may affect focal pattern. 相似文献