共查询到20条相似文献,搜索用时 15 毫秒
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The scattering and focusing characteristics of a Gaussian beam with phase distribution is studied by a stepped index Luneberg lens. A model experiment was performed using a six-layer spherical lens. Two kinds of beams, that is, broad and narrow beam are examined for the incident Gaussian beam. We find that focusing effect of a narrow beam is wholly lower than that of a broad beam. The focal point is also shifted toward outer of sphere because of phase lag for the beam source. The spot size equals almost the wavelength for the various beam parameters. 相似文献
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根据广义米氏理论,将入射的高斯波束按矢量球谐函数展开,获得了波束因子(展开系数)gmn,TM和gmn,TE的一般表达式。应用gmn的局域近结果和散射系数anm和bnm的迭代公式与算法,研究了多层有耗介质球的光散射。讨论了波束宽度与球形粒子的尺寸和位置对散射系数和散射强度角分布的影响。 相似文献
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两个相邻目标对平面波、高斯波束的光散射 总被引:3,自引:0,他引:3
基于等效原理和互易性定理研究了两个靠近目标对平面波、高斯波束的光散射问题,给出了这一复合光散射模型的二阶散射结果。通常一阶散射结果容易求解,但由于耦合效应的复杂性,很难给出二阶散射结果的解析形式。为了解决这一问题,应用互易性定理给出了求解任意相邻介质目标二阶散射场的公式,同时借助等效原理将求解散射场公式中的体积分简化为面积分的形式,从而降低了求解难度。求解了两相邻球形粒子的复合散射场,并将求解结果与应用时域积分方程法求得的结果进行了比较。同时,还讨论了束腰半径、目标位置对散射截面及偏振度的影响。 相似文献
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不均匀柱形粒子的光散射特性研究对复杂结构粒子参量的反演具有重要意义。基于德拜理论,对在轴高斯波束垂直入射无限长多层圆柱的散射特性进行了讨论。获得了散射系数的德拜级数展开式;并利用该公式分别计算了均匀和双层圆柱的总散射强度角分布,德拜级数单阶散射强度角分布;总散射强度结果与广义米氏理论(GLMT)进行了比较,两者吻合很好。分析表明圆柱散射强度不同散射角区间的值来自德拜级数不同阶的散射强度贡献;双层圆柱各层半径和折射率的值对德拜级数二阶散射强度角分布中峰值的出现起决定作用。当双层圆柱的外层较薄时,在120°~150°之间会出现两个明显峰值,即出现双重一阶彩虹峰值;反之,当外层厚度大于内层时,只有一个峰值存在。 相似文献
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YunFei Lui ShengCai Shi ShengLin Yu 《International Journal of Infrared and Millimeter Waves》2002,23(12):1727-1742
In this paper, the scattering formulae of a Gaussian electromagnetic beam by a cylindrical wire grid are derived. For the summation of Hankel functions, we adopt an integral form of lattice sums, which is developed by Yasumoto and Yoshitomi, to speed up convergence. The reflected and transmitted characteristics of a Gaussian beam by an actual wire grid are thoroughly investigated. Detailed simulation results are presented. 相似文献
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Rainbow Scattering by an Inhomogeneous Cylinder with an Off-Axis Gaussian Beam Incidence at Normal 总被引:1,自引:0,他引:1
The problem of an off-axis Gaussian beam incident perpendicular on an infinitely long multi-layered cylinder is investigated. The efficient and accurate recursive algorithm for computing the scattering field is discussed. The stability of the numerical scheme allows us to extend the feasible range of computations, both in size parameter and in number of layers for a given size. Particular attention is paid to rainbow scattering of homogeneous and inhomogeneous fibers. 相似文献
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Restoration of Decentered Gaussian Beam with the Combination of a Lens and a Gaussian Aperture 总被引:1,自引:0,他引:1
1 Introduction TheGaussianbeamisthefundamentalshapeofthelaserwithaspherical mirrorresonatorandwidelyusedtodescribeasinglemodelaser.Intheparaxialapproximation ,thedistributionofcomplexamplitudeofitremainsunchangedwhenitundergoestheFouriertransformorthe… 相似文献
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Based on the plane wave analysis and the superposition of the plane waves, the diffraction of a Gaussian beam by a periodic screen with a dielectric plate is analyzed. The reflection power coefficient for different parameters of the beam and the screen is given. When the beam waist size is increased the results reaches that of the plane wave. It has been found that the power reflection coefficient is not sensitive to the beam waist size, however, it is sensitive to the period of the grating and polarization angle. 相似文献
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Y. Yan 《International Journal of Infrared and Millimeter Waves》2001,22(3):459-468
A theoretical investigation of scattering characteristics of millimeter waves from acid rain is conducted using the method of vector spherical function expansion. The particles of acid rain are considered as the double-layered spheroid. The method is used to derive an analytical solution to the problem of scattering of millimeter waves by a coated dielectric spheroid. The normalized bistatic cross section versus scattering angle for the acid raindrop is calculated at frequencies of 35 GHz and 94 GHz. This is the first part of our study scattering characteristics of millimeter waves from acid rain. 相似文献
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Based on the orthogonalities of the vector wave functions, the expressions of scattering fields are developed as the particle in the zero order field and in the first order fields of x, y, and z, respectively. A general relation between the expansion coefficients of scattering field and incident field is presented. Taking the elliptical beam for example, the scattering property of a particle in beam is investigated. After analyzing the effects of the beam waist, irradiating distance, etc. on scattering property, the validity of the proposed algorithm is demonstrated. Results show that the beam waist may improve the particle identification property and the particle has a strong scattering both in the forward direction and in the backward direction. The method proposed is simple and is a new way of researching the scattering from particles in electromagnetic beams. 相似文献
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K. V. Artem’ev G. M. Batanov N. K. Berezhetskaya V. D. Borzosekov L. V. Kolik E. M. Konchekov I. A. Kossyi D. V. Malakhov A. E. Petrov K. A. Sarksyan V. D. Stepakhin N. K. Kharchev 《JETP Letters》2018,107(4):219-222
The propagation velocities of a subthreshold discharge excited in air at atmospheric pressure by a pulsed microwave beam with a Gaussian field distribution, a wavelength of 4 mm, and an intensity up to 30 kW/cm2 have been measured by means of optical and microwave diagnostics. It has been shown that the motion of a discharge front along the path of the beam toward the region of an increasing microwave field is accompanied by an increase in the velocity from subsonic (~10–4 cm/s) to supersonic (~(6–8) × 104 cm/s). At the same time, motion toward the decreasing field region is accompanied by a decrease in the velocity from supersonic to subsonic. It has been found that the maximum temperature of the gas in the discharge at velocities of ~104 cm/s reaches ~5.3 kK. 相似文献
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Chen Hui Wu Zhensen Yang Ruike Bai Lu 《International Journal of Infrared and Millimeter Waves》2004,25(3):523-529
The coherent and incoherent scattering cross sections of Infrared Laser Gaussian beam scattering from arbitrarily shaped convex dielectric objects with rough surfaces are investigated by using plane wave spectrum method and physical optics approximation. In the paper, the infrared laser scattering cross sections of rough sphere are calculated at 10.6 m , and the influence of the beam size, permittivity, and polarization as well as roughness parameters is analyzed numerically. When the beam size is much larger than the size of object, the results in the paper can reduce to those of an incident plane wave. On the other hand, for the case of roughness statistical parameter close to zero, only the forward scattering has a parent difference compared with the result of gaussian beam scattering from smooth sphere. 相似文献
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Huayong Zhang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(9):1486-1491
A generalized Lorenz-Mie theory framework (GLMT) is applied to the study of Gaussian beam scattering by a spherical particle with an embedded spheroid at the center. By virtue of a transformation between the spherical and spheroidal vector wave functions, a theoretical procedure is developed to deal with the boundary conditions. Numerical results of the normalized differential scattering cross section are presented. 相似文献
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S. Van den Bulcke L. Zhang A. Franchois J. M. Geffrin J. Stiens 《International Journal of Infrared and Millimeter Waves》2008,29(11):1038-1047
For the development of millimeter wave imaging systems, it is important to be able to simulate some representative scattering
configurations. Typically, Gaussian beams are used in active imaging systems. Since these beams only illuminate a spatially
limited region, many objects can be treated as infinitely long 2D (in)homogenous cylinders. However, the incident Gaussian
beams have a 3D character. Therefore, a dedicated 2.5D scattering simulator was developed. In this paper, simulation results
obtained with this simulator are compared to measurements obtained from a bi-static microwave set-up and from a W-band millimeter
wave set-up. Comparison of simulations and measurements proves that the 2.5D algorithm is a good simulation tool to study
scattering of long inhomogeneous cylinders, illuminated by 3D plane waves or 3D Gaussian beams under different elevation angles. 相似文献