The Imbert-Fedorov shift of paraxial light beams

We present a solution to the problem of reflection and transmission of a polarized paraxial light beam at an interface between two homogeneous media by using a two-form amplitude and an extension matrix to represent the vectorial angular spectrum of a three-dimensional (3D) light beam. We derive general formulas for the Imbert-Fedorov (IF) shift of the reflected and transmitted beams of a polarized paraxial light beam. The IF shift of two different types of polarized beams is calculated, and the influence of the polarization state and the polarization feature of the vectorial angular spectrum on the IF shift is discussed.     

任意偏振态光束全反射时的侧向和横向位移

光束在电介质界面发生全反射时,实际反射光束会在入射面内相对于几何反射光束产生一侧向位移,在垂直于入射面的方向产生一横向位移。利用改进的能流法研究了任意偏振态光束发生全反射时的侧向和横向位移特性。研究表明,侧向位移的大小与入射光束的两组成部分———TE和TM偏振光的相位差无关,而与两组分的光强比密切相关,且该位移可以表示为TE和TM偏振光束各自的位移按光强的加权平均。横向位移的大小不仅与入射光束两组分的光强比相关,还与组分的相位差密切相关。另外,反射光束不仅在椭圆偏振态入射的情况下会产生横向位移,而且在TE和TM偏振态之外的其他线偏振态入射时,也会产生横向位移。     

光自旋霍尔效应中横移的影响因素研究

研究了光束在空气与电介质分界面传输产生的自旋霍尔效应,揭示了光束重心横移分别与偏振态、折射率差以及入射角三者之间的定性关系.研究发现各光场横移都随偏振参量增大而增大,左、右旋椭圆偏振光的横移等值反向,圆偏振态下的横移比椭圆偏振态下的横移大.改变折射率差的大小,反射光横移随折射率差的增大而减小,但当折射率差接近零时,反射...     

光学马格努斯效应中的横向角移分析

从平面角谱理论出发,建立了光束在空气和玻璃界面折射的传输模型.基于这一模型,揭示了光学马格努斯效应中的横向角移现象.对于特定的线偏振和椭圆偏振光束,其折射场重心出现了横向角移,而当入射光束为圆偏振时,横向角移则会消失.在正负折射率界面,光束的横向角移产生了反转现象,这是由于光束在左手材料中发生了负衍射.超高折射率可明显地减少横向角移,而超低折射率则可显著地增强横向角移.这些发现将为如何调控和增强光学马格努斯效应提供理论依据. 关键词： 光学马格努斯效应 横向角移 圆偏振     

Fedorov lateral shift at the interface between left-handed and right-handed media

The Fedorov lateral shift of a polarized beam upon the total internal reflection of light from an interface between media with positive and negative refractive indices is investigated. It is shown that the Fedorov lateral shift depends substantially on the polarization of the incident beam. The prediction is made that the Fedorov lateral shift can be completely compensated upon the total internal reflection of linearly polarized modes from two boundaries of a planar waveguide with a substrate prepared from a left-handed material.     

Reflection and transmission of Laguerre Gaussian beam from uniaxial anisotropic multilayered media

Based on angular spectrum expansion and 4 × 4 matrix theory, the reflection and transmission characteristics of a Laguerre Gaussian(LG) beam from uniaxial anisotropic multilayered media are studied. The reflected and transmitted beam fields of an LG beam are derived. In the case where the principal coordinates of the uniaxial anisotropic media coincide with the global coordinates, the reflected and transmitted beam intensities from a uniaxial anisotropic slab and three-layered media are numerically simulated. It is shown that the reflected intensity components of the incident beam, especially the TM polarized incident beam, are smaller than the transmitted intensity components. The distortion of the reflected intensity component is more evident than that of the transmitted intensity component. The distortion of intensity distribution is greatly affected by the dielectric tensor and the thickness of anisotropic media. We finally extend the application of the method to general anisotropic multilayered media.     

Enhancement of cross-polarized beam components at a metamaterial surface

Beam-interface interactions under incidence of a TE polarized elegant Hermite–Gaussian beam are considered in order to obtain efficient excitation of higher-order beam modes at a homogeneous, isotropic metamaterial surface. It is shown by numerical simulations that two transmitted TE and TM polarization beam components are enhanced more efficiently at a metamaterial surface than in the case of a dielectric interface. The mixed Poynting vector contribution to the incident energy flux is evaluated to explain this enhancement. The numerical results obtained are verified against energy balance at the interface.     

Tightly focusing of spirally polarized Quadratic Bessel Gaussian beam through a dielectric interface

Based on vector diffraction theory, the tight focusing properties of spirally polarized axisymmetric Bessel-modulated Gaussian beam through a dielectric interface on high numerical aperture (NA) are investigated theoretically. The optical intensity distribution in the focal region of high NA objective lens is investigated in detail by numerical calculations. The results show that the focal shift induced in the focal region is by mismatch of refractive indices across the dielectric interface. It is also found that the optical intensity in focal region of spirally polarized Quadratic Bessel Gaussian (QBG) beam can be altered considerably by changing spiral parameter C that indicates the polarization spiral degree of the incident beam.     

The propagation of a polarized gaussian beam in a smoothly inhomogeneous isotropic medium

In the frame of the eikonal-based complex geometrical optics, which describes the phase front and cross section of a light beam using the quadratic expansion of a complex-valued eikonal, we investigate the transverse deflections of a polarized Gaussian beam (GB) in a smoothly inhomogeneous isotropic medium, which is called the spin Hall effect of the beam. The linear complex-valued eikonal terms are introduced firstly to describe the polarization-dependent transverse shifts of the beam in the inhomogeneous medium. We find that the polarization-dependent transverse shifts of the beams include two parts: one originates from the coupling between the spin angular momentum and the extrinsic orbital angular momentum due to the curve trajectory of the center of gravity of the polarized GB, and the other from the coupling between the spin angular momentum and the intrinsic orbital angular momentum due to the rotation of the beam with respect to the central ray.     

Non-geometrical effects on Gaussian beams transmitting through a thin dielectric slab

It is shown that a Gaussian light beam transmitting through a planar thin dielectric slab in the air undergoes four different effects, i.e. lateral Goos-Hanchen-like （GHL） displacement, angular deflection, width modification and longitudinal focal shift as compared with the results predicted by geometrical optics. According to the Taylor expansion of the exponent of transmission coefficient when expressed as an exponential form, the lateral GHL displacement and the angular deflection are the first-order effects and can be negative or positive. The width modification and the longitudinal focal shift are the second-order effects and can also be positive or negative. Owing to the waist-width dependent term, the non-geometrical effects of transmitted beam are not identical with the non-specular effects of reflected beam. The conditions for the validity of those effects are suggested and numerical simulations are also given.     

拟合法测量高斯光束的束腰半径

从高斯光束的横向光强分布特性出发,建立了小孔光阑透过功率与孔径的关系式.采用2种不同拟合方法对高斯光束的束腰半径进行了测量.为减小激光器功率不稳定带来的不利影响,实验中采用双光路进行测量.结果表明,用拟合法测量高斯光束的束腰半径不仅合理,而且可行.     

非均匀关联径向偏振部分相干光的产生

从理论和实验两方面对非均匀关联径向偏振部分相干光的产生进行了研究.理论上,基于相位关联与相干度的联系,推导出了非均匀关联径向偏振部分相干光的2×2阶交叉谱密度矩阵及相干度分布.实验上,利用一个相位型液晶空间光调制器的不同区域,对入射的完全相干的径向偏振光的两个正交偏振分量分别加载随机相位调制,并实验测量了这种光束的相干度分布及其对光强分布的影响.实验结果验证了光束相干度的非均匀关联结构,并且通过改变随机相位的高斯调制半宽可以改变光束的相干性分布.研究表明,随着随机相位的高斯调制半宽的增加,光束中两点间的相干度逐渐减小,其光强分布由圆环状逐渐变化为类平顶的光强分布.这种非均匀关联的径向偏振部分相干光在激光微操纵和材料加工等领域具有一定的潜在应用价值.     

Radially polarized hyperbolic-cosine-Gaussian beam

Vector beams have attracted much interest recently. In this paper, focusing properties of the radially polarized hyperbolic-cosine-Gaussian beam are investigated. Simulation results show that the focal depth increases with increasing cosine parameter in the cosine term of the beam, while focal spot decreases simultaneously, namely, superresolution occurs. Focal depth increase velocity is quicker for larger cosine parameter, while the transverse focal spot shrinks more quickly for smaller cosine parameter. In addition, for two-portion concentric piecewise radially polarized hyperbolic-cosine-Gaussian beam with π phase shift in center circle portion, focal pattern evolves considerably with increasing cosine parameter, and the evolution principle differs for different radius of the center circle portion. Focal splitting and novel focal spots may appear. This kind of vector beam can be used in optical storage, optical manipulation, and lithography.     

端面抽运板条介质抽运光束不均匀性及改善方法研究

 基于Zemax软件下的非序列模式(non-sequential mode)光线追迹法,分别模拟复合结构板条介质抽运端面和掺杂介质区工作端面上的光强度分布。由追迹结果可知,经过整形,在抽运面强度分布均匀的抽运光束经过非掺杂介质区传播到掺杂介质工作端面后光束分布均匀性大大降低。研究表明复合结构板条介质中非掺杂介质区影响了抽运光束,即抽运光在非掺杂介质区传播过程中发生全内反射,导致部分光束在实际工作端面的部分区域发生叠加,从而致使实际工作端面抽运光束分布不均匀。最后,依据平面波导匀化理论,从改变非掺杂介质区长度和入射光束发散角大小角度出发,提出改善抽运光束均匀性的思路,并进行了模拟验证。     

Total internal reflection of a Gaussian light beam

An approximate theoretical model for calculating the reflected and refracted fields of a Gaussian light beam at a plane interface between two isotropic media is formulated on the basis of a Fourier integral. In the vicinity of the critical angle of incidence (for total internal reflection) the model predicts the presence of two refracted beams, one displaced along the interface by an amount equal to the Goos-Hänchen shift; curvature of the phase fronts and nonalignment of the effective directions of energy and phase propagation occur for each beam, as in an anisotropic medium.     

左手材料中圆偏振光束的反常旋转特性研究

根据Whittaker标量势理论,建立了圆偏振光束的矢量传输模型.基于这一模型研究了圆偏振光束在左手材料中的反常旋转特性.通过分析光束偏振态、衍射对强度质心旋转特性的影响,发现圆偏振光束在左手材料中旋转方向反转并揭示其旋转角等于古伊相.采用分析横向能流的方法,揭示左手材料中反向的横向能流是导致反常旋转特性的主要原因.对圆偏振光束在左手材料中反常旋转特性的研究,有利于增强对左手材料中光束传输特性的认识. 关键词： 左手材料 圆偏振光束 旋转特性     

Wavelength-dependent intensity distribution of a Gaussian beam scattered by a spherical particle

The wavelength-dependent intensity of a light beam scattered by an isotropic homogeneous particle illuminated with an on-axis monochromatic polarized Gaussian beam is calculated in this paper. The vector spherical harmonics expansion and T transformation matrix are used to form the theoretical basis. Numerical results show that the angular intensity distribution is symmetric for an on-axis polarized Gaussian beam illumination upon an aqueous spherical particle at 473, 532 and 660 nm. For the specified aqueous spherical particle, the scattered intensity distribution decreases with increase in wavelengths.     

基于金属狭缝阵列的各向异性偏振分束器

在金属-电介质结构的基础上提出了一种基于金属狭缝阵列的各向异性偏振分束器,并采用有限元法研究了横磁(TM)和横电(TE)偏振光入射后结构所表现出的负反射和镜面反射等特性.计算结果表明,当偏振光的入射角设定在20?—70?时,入射的TM光发生强烈的负反射,而TE光的负反射很弱,并随着波长的增加而急剧下降.分析可得偏振分束光栅的理想负反射点和反射面的完美对称响应效果.通过仿真得到了理想负反射点的取值范围.结合严格耦合波法软件,计算不同偏振光入射时负反射和镜面反射条件下的反射率,其消光比高达10~6.     

Concentric piecewise azimuthally polarized beam by a pure phase plate

Focusing properties of the azimuthally polarized beam induced by a pure phase plate are investigated theoretically. The pure phase plate consists of two concentric portions, one center circle portion and one outer annular portion, through which the azimuthally polarized beam passed evolves into concentric piecewise azimuthally polarized beam. When the phase shift of the center portion is π, one ring focus may evolve into novel focal patterns with increasing radius of the center circle portion, such as cylindrical crust focus, two-ring focus, and three-ring focus. And if the geometrical parameters are unchanged, focal patterns also changes considerably with tunable phase of the center portion. Ring focus shifts along the optical axis on the increasing phase. Some optical gradient force distributions and dependence of focal shift on phase shift are also illustrated. This kind of concentric piecewise azimuthally polarized beam can be used in optical manipulation technology.     

Lateral displacement of a Gaussian beam reflected from absorbing media

Lateral displacements of well-focused beams reflected from absorbing media are demonstrated in this paper. The incident beam is modeled as a tapered wave with a Gaussian spectrum. The field solutions are obtained on both sides of the interface by solving analytically from Maxwell's equations and by matching the boundary conditions at the interface. Numerical simulations are presented and the field values as well as the time-averaged power densities are computed. The influences of the polarization, the angle of incidence and the beam width on the displacement are discussed. The origin of the displacement lies in the absorption of the media, for which there is a phase shift between the incident and reflected waves. Because of this phase shift, the center of the reflected beam does not coincide with that of the incident one, similar to the Goos-Hänchen shift.