On-axis Gaussian beam scattering by an eccentrically coated conducting cylinder

Based on the generalized Lorenz–Mie theory (GLMT) framework, an exact analytic solution to electromagnetic scattering by an eccentrically coated conducting cylinder is constructed, for oblique incidence of an on-axis Gaussian beam described by a localized beam model. The solution is found by the classical separation of variables technique and the translational addition theorem. For a tightly focused Gaussian beam propagating perpendicularly to the cylinder axis, numerical results of the normalized differential scattering cross section are presented, and the scattering characteristics are discussed concisely.     

Scattering characteristics of conducting cylinder coated with nonuniform magnetized ferrite

An analytical technique, referred to as the scattering matrix method （SMM）, is developed to analyse the scattering of a planar wave from a conductolution for the nonuniform fering cylinder coated with nonuniform magnetized ferrite. The SMM srite coating can be reduced to the expressions for the scattering and penetrated coefficients in four particular cases： nonuniform magnetized ferrite cylinder, uniform magnetized ferrite-coated conducting cylinder, uniform ferrite cylinder as well as homogeneous dielectric-coated conducting cylinder. The resonant condition for the nonuniform ferrite coating is obtained. The distinctive differences in scattering between the nonuniform ferrite coating and the nonuniform dielectric coating are demonstrated. The effects of applied magnetic fields and wave frequencies on the scattering characteristics for two types of the linear profiles are revealed.     

在轴高斯波束入射无限长多层圆柱散射的德拜级数解

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。     

Scattering of a Gaussian electromagnetic beam by a thin semiconducting cylinder

The scattering of a three-dimensional Gaussian electromagnetic beam by a thin (compared to the wavelength) semiconducting cylinder of infinite length is considered. Expressions for the scattered field and for the current induced in the cylinder are obtained. A numerical analysis of the distribution of the secondary current along the cylinder axis was made. It is shown that the dependence of the induced current on the distance along the cylinder axis becomes Gaussian as the aperture of the incident beam is increased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 78–80, January, 1991.     

Scattering of a First-Order Gaussian Beam by an infinite cylinder with arbitrary location and arbitrary orientation

The theory of scattering of a first-order Gaussian beam by an infinite cylinder with arbitrary location and arbitrary orientation is presented. A component of the theory is the use of the theory of distributions.     

Debye Series of Scattering by a Multi-Layered Cylinder in an Off-Axis 2D Gaussian Beam

The Debye series of light scattering by an infinite multi-layered cylinder in an off-axis 21） Gaussian beam is studied. A simplified but rigorous iterative formula for scattering coefficients is presented. The numerical calculations of scattering intensity by a cylinder in on-axis and off-axis beams are developed. It is indicated that the results of Debye series reach an agreement with those of generalized Lorenz-Mie theory and the off-axis distances vary the results to a great extent. The Debye series components of a two-layered cylinder are further discussed. The relations between them with rainbow phenomena are analysed.     

Scattering of shaped beam by a conducting infinite cylinder with dielectric coating

Based on the generalized Lorenz–Mie theory (GLMT), which provides the general framework and expansion of the incident shaped beam in terms of cylindrical vector wave functions, an analytic solution to the electromagnetic scattering by coated infinite cylinders is constructed for arbitrary incidence of a shaped beam. As an example, for a tightly focused Gaussian beam propagating perpendicularly to the cylinder axis, the scattering characteristics that obviously demonstrate the three-dimensional nature are described in detail, and numerical results of the normalized differential scattering cross section are evaluated.     

Scattering of a Gaussian beam by an anisotropically coated circular cylinder

A solution to the problem of Gaussian beam scattering by an anisotropically coated circular cylinder is presented. The incident Gaussian beam source is expanded as an approximate expression in the simple form with a Tayor’s series. The transmitted field in the anisotropically coated region is expressed as a infinite summation of eigen plane waves with different polar angles. The unknown coefficients of the scattered fields are obtained with the aid of the boundary conditions. The infinite series can be truncated under the prerequisite of achieving the solution convergence. Only the case of transverse-electric polarization is discussed. The similar formulation of transverse-magnetic polarization can be obtained by adopting the similar method. Some numerical results are presented and discussed. The result is in agreement with that available as expected when the Gaussian beam degenerates to a plane wave incidence case.     

Rainbow Scattering by an Inhomogeneous Cylinder with an Off-Axis Gaussian Beam Incidence at Normal

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.     

Arbitrary direction incident Gaussian beam scattering by multispheres

Based on spherical vector wave functions and their coordinate rotation theory,the field of a Gaussian beam in terms of the spherical vector wave functions in an arbitrary unparallel Cartesian coordinate system is expanded.The beam shape coefficient and its convergence property are discussed in detail.Scattering of an arbitrary direction Gaussian beam by multiple homogeneous isotropic spheres is investigated.The effects of beam waist width,sphere separation distance,sphere number,beam centre positioning,and incident angle for a Gaussian beam with two polarization modes incident on various shaped sphere clusters are numerically studied.Moreover,the scattering characteristics of two kinds of shaped red blood cells illuminated by an arbitrary direction incident Gaussian beam with two polarization modes are investigated.Our results are expected to provide useful insights into particle sizing and the measurement of the scattering characteristics of blood corpuscle particles with laser diagnostic techniques.     

A review of the numerical investigation on the scattering of Gaussian beam by complex particles

The study of light scattering by various particles is an active and important subject of research with myriad practical applications. During the years the scattering of plane wave by various particles has been investigated extensively. In recent years, with the development of laser sources and the tremendous expansion of their application, there has been a growing interest in the study of light scattering by various particles illuminated by a focused Gaussian beam. Since the analytical methods are only suitable for the analysis of Gaussian beam scattering by some regular particles, for complex particles with arbitrary shape and structure, one has to resort to the numerical methods. In this article, we review the recent numerical investigation on the scattering of Gaussian beam by systems of complex particles, including arbitrarily shaped conducting particles, dielectric particles, composite particles with inclusions, as well as random discrete particles and fractal soot aggregates. The essential formulations of the proposed numerical methods are outlined and the numerical results for some complex particles are also presented. This review is expected to provide useful help for the study of the interaction between the laser beams and the complex particles.     

扭曲光束的产生及表征

对于光斑主轴在传输过程中不停变化的扭曲光束,采用光斑主轴方向上的光束传输比对光束质量等特性进行表征和描述并不全面。针对扭曲高斯光束,在光束传输矩阵的理论计算的基础上,研究了通过双柱透镜产生扭曲光束的方法;推导得到了光束在交叉方向上光束传输比的表达式,并定义了一个新的物理量-光束的扭曲系数;分别采用光束传输矩阵和数值模拟,得到了不同柱透镜之间夹角和间距下的扭曲系数,通过光束传输比和扭曲系数共同对扭曲光束进行表征。结果表明,相比于单纯的光束传输比,两者的组合能够更好地对扭曲光束进行表征。通过实验对理论和仿真结果进行了验证,理论结果和实验结果相符。     

二维高斯波束对多层球粒子电磁散射的解析解

基于矢量波函数在球和柱坐标系中表达式之间的转换关系,提出了一种求解球坐标系中二维高斯波束波形因子的方法,得到了二维高斯波束波形因子在球坐标系中的解析公式.结合广义米理论推导了在轴二维高斯波束入射多层球粒子的电磁散射的解析解,并对散射强度随散射角的分布进行了数值模拟,结果与平面波入射情况进行了比较. 关键词： 矢量波函数 波形因子 电磁散射 广义米理论     

双球粒子对任意入射单波束及双波束的散射

基于广义Lorenz-Mie理论,研究了双介质球粒子对任意角度入射波束的散射.将入射波束用球矢量波函数展开,推导了双介质球形粒子对任意入射单波束的散射方程;将该方法进一步推广,研究了双波束任意入射时的情况.以Gauss波束为例,对以上理论进行了数值验证,比较分析了单波束及双波束任意入射时散射特性随入射方向、球心距等参数的变化关系.     

双球粒子对任意入射单波束及双波束的散射

基于广义Lorenz-Mie理论,研究了双介质球粒子对任意角度入射波束的散射.将入射波束用球矢量波函数展开,推导了双介质球形粒子对任意入射单波束的散射方程;将该方法进一步推广,研究了双波束任意入射时的情况.以Gauss波束为例,对以上理论进行了数值验证,比较分析了单波束及双波束任意入射时散射特性随入射方向、球心距等参数的变化关系. 关键词： 广义波束因子 双球粒子 Gauss波束     

Radiation pressure over dielectric and metallic nanocylinders on surfaces: polarization dependence and plasmon resonance conditions

Multiple scattering calculations of the electromagnetic force and the potential energy exerted by an evanescent field on a nanometric cylinder over a dielectric interface, as well as by a propagating Gaussian beam, are carried out. These calculations constitute a model that describes the gradient, scattering, and absorption components of the force in an elongated particle. The attractive or repulsive nature of the force is strongly dependent on the polarization of the incident field for a metallic particle, whereas a dielectric particle is only weakly attracted to high-intensity regions. Excitation of plasmon resonance in a metallic particle enhances both the scattering and the absorption components of the force, whereas it diminishes the gradient-force component.     

粗糙体目标激光束散射场的互相关函数统计特征

依据高斯波束体目标散射特征,研究了粗糙体目标高斯波束散射场量的互相关函数统计特征。在激光波束入射下,通过数值方法讨论圆球类目标、不同半径、不同材料、不同入射波束极化等条件下,散射场量的互相关函数随散射角变化情况。数值计算结果表明:金属薄膜材料比非金属镀漆材料互相关函数量值要大,金属材料球体目标的后向散射互相关函数值较大,而非金属镀漆材料球体互相关函数值较小。材料表面的粗糙度和目标尺寸对互相关函数影响较大,而入射光的极化方式对相关函数有影响但影响较小。     

Scattering of on-axis polarized Gaussian light beam by spheroidal water coating aerosol particle

Small particle light scattering can produce light with polarization characteristics different from those of the incident beam. An analytical solution to the scattering by a spheroid with inclusion for an on-axis polarized Gaussian beam incidence is provided within the generalized Lorenz-Mie theory framework. The shapes of the inclusion can be spherical, confocal spheroid, or non-confocal spheroid. The Muller scattering matrix elements are computed for plane wave incidence or Gaussian light beam incidence. The effect of the size and shape of the inclusion or the coating on the polarized Oaussian light scattering characteristics by a spheroidal water coating aerosol Darticle are commlted and a,nalvzed.     

Microwave scattering diagrams of three-layered SiC-metamaterial/gyrotropic ferrite-SiC cylinders

We present here for the first time the rigorous solution of the boundary diffraction problem of microwave scattering by a multilayered 2D cylinder. The cylinder layers may be made of isotropic, uniaxial anisotropic, electrically and (or) magnetically gyrotropic materials. The number and thickness of the layers may have arbitrary values in our solution. We calculated scattering diagrams (a radial component of real part of the Poynting vector) inside and outside of cylinder using the solution. Here we present scattering diagrams from a three-layered cylinder made of SiC and metamaterial or saturate magnetized ferrite. Diagrams were computed for wave incidence angles θ=π/2,π/3,π/6 inside of metamaterial/ferrite layer at a distance of 1 mm and outside of cylinder at a distance of 2.5 mm from the cylinder axis.