Features of evanescent Bessel light beams formed in structures containing a dielectric layer

Based on the matrix method, a theory of generation of evanescent Bessel light beams (BLBs) in a structure containing a dielectric layer is developed. An exact solution is obtained for the problem of the tunneling of vector BLBs (TE and TM modes and their linear superposition) through the layer surrounded by various dielectric media in conditions of the total internal reflection at its boundaries. The behavior of energy fluxes both inside the layer and in ambient media is investigated.     

Giant lateral shift of a light beam at the defect mode in one-dimensional photonic crystals

It is found that when a light beam is incident on a one-dimensional photonic crystal (1DPC) containing a defect layer, the lateral shifts of both the reflected and the transmitted beams are greatly enhanced near the defect mode of the 1DPC, whose location depends on the angles at a fixed frequency. The effect was studied by use of a Gaussian beam. The giant lateral displacement is due to the localization of the electromagnetic wave.     

A controlled conical lens for the formation of Bessel light beams

The possibility of the formation of zero-order Bessel light beams using a uniaxial crystal with cylindrical electrodes is investigated. It is shown that, if a given polarization distribution is provided in the incident beam, a Bessel light beam with the cone angle controlled by an external electric field is formed. It is proposed to use this result for the matching of the axicon parameters and creation of conical lenses with an adjustable cone angle.     

Ultrasonic diffraction of Bessel light beams in uniaxial gyrotropic crystals

Specific features of the acousto-optic diffraction of Bessel light beams propagating in the vicinity of the optical axis of a uniaxial gyrotropic crystal have been investigated. The dependences of the diffraction efficiency on the acousto-optic interaction length, ultrasound power, and polarization state of the incident Bessel light beam have been analyzed using the coupled-wave equations and the overlap-integral method. It is shown that polarization-independent diffraction of Bessel light beams is observed in paratellurite crystals, when the Bragg diffraction efficiency is independent of the polarization state of the incident beam. The physical reason for this diffraction has been established (both theoretically and experimentally) to be simultaneous implementation of two processes of anisotropic scattering, at which the Bragg synchronism conditions are satisfied for orthogonal polarized Bessel beams with elliptical polarization.     

像散Bessel光束自重建特性的理论和实验研究

基于菲涅耳衍射积分理论和巴比涅原理,推导出像散Bessel光束经圆形障碍物后的光强分布一般表达式.数值模拟了像散Bessel光束经圆形障碍物遮挡后光场的自重建过程,并设计相关实验进行验证,实验结果与理论模拟基本符合.结果表明：零阶像散Bessel光束经过轴上和离轴障碍物后均会发生光束重建现象.随着传输距离的增加,像散Bessel光束的外轮廓尺寸变大、中心光点阵列数增多,逐渐重建出不同于障碍物前的完整光束.并且观察到光束在重建过程中横向和纵向的重建速度并不一致,存在一定的速度差.利用螺旋相位板产生高阶像散Bessel光束,验证了高阶像散Bessel光束经障碍物遮挡后同样具有自重建特性.研究结果对像散Bessel光束在多层面粒子操纵方面的应用具有参考价值.     

Self-action of Bessel light beams in cubic gyrotropic photorefractive crystals

We have studied conversion and interaction of a Bessel laser beam of zero order in photorefractive crystals. We have established that in a cubic gyrotropic crystal, two Bessel light beams propagate with different wave vectors and cone angles, but with identical conicity parameters. As the power in the Bessel light beam increases, we have experimentally observed a new optical effect: self-action of a Bessel light beam. We have studied the effect of external influences and the parameters of the beam itself on the process of self-refraction in photorefractive crystals. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 488–493, July–August, 2006.     

Evanescent Bessel beam generation through filtering highly focused cylindrical vector beams with a defect mode one-dimensional photonic crystal

We propose a simple setup for generating evanescent Bessel beams using the defect mode of one-dimensional (1D) photonic crystal. The angular selectivity provided by the defect mode mimics the role of an axicon for Bessel beam generation. When an azimuthally polarized beam is strongly focused onto a 1D defect mode photonic crystal interface, an evanescent Bessel beam of the first-order is produced, while an evanescent Bessel beam of the zeroth-order will be created under a radially polarized beam illumination. Switching between a donut shape and a solid focal distribution can be easily realized by controlling the polarization of the illumination. Such a versatile evanescent Bessel beam generation may find potential applications in optical trapping.     

Efficient conical emission of stimulated Raman Stokes light generated by a Bessel pump beam

Stimulated Raman scattering in H(2) gas was studied with a Bessel pump beam, which was generated with a binary phase grating. The first Stokes light was emitted along the surface of a cone, the angle of which was equal to the cone angle of the Bessel pump beam multiplied by the ratio of the wavelengths of the Stokes and pump beams. High conversion efficiency into the first Stokes light of as much as 60% was achieved, indicating that the complete Bessel J(0) mode of the pump beam is involved in the stimulated scattering process.     

Spin Hall effect of light in one-dimensional photonic crystal

We established a general propagating model to investigate the spin Hall effect of light in one-dimensional photonic crystal. A polarized (spin dependent) Gaussian beam which was incident obliquely through one-dimensional photonic crystal was demonstrated. Having decomposed a polarized Gaussian beam into different plane wave components charactering individual wave vectors, we revealed the transmission coefficient and reflection coefficient of each plane wave which propagates through the one-dimensional photonic crystal. It enabled us to obtain exact solution to the electric field of transmitted and reflected beams, and the analytical formula of light intensity, accordingly. A method based upon the partial differentials with the intensity distribution of the transmitted and reflected Gaussian beams was presented to determine the transverse and longitude shifts explicitly. Spin dependent shifts in one-dimensional photonic crystal provide alternative evidence for the spin Hall effect of light.     

一种含时贝塞尔光束的理论性质研究

本文从理论角度提出了一种"含时贝塞尔光束"的概念.在非傍轴和非时谐条件下,直接从麦克斯韦方程出发,借鉴半贝塞尔光束的处理方法,同时引入第四维虚数坐标,由此获得了完整的"含时贝塞尔光束"的解析表达式.并从无衍射性质和时空特性两个方面对其进行了探讨和研究,发现该光束具有如下性质:符合贝塞尔光束类型的无衍射特征;在时空双曲线上强度保持不变;光波时空特性的临界条件类似于相对论中的光锥."含时贝塞尔光束"的概念为无衍射自加速光束的研究开拓了新的思路和方向.     

Generation of the Second Harmonic by Bessel Light Beams Under the Conditions of Quasisynchronism

The specific features of the doubling of Bessel light beams in quasisynchronous interaction in periodically polarized nonlinear crystals are investigated. A theoretical model has been developed, which is based on the representation of the second-harmonic field in the form of superposition of Bessel beams. Based on the analysis of overlapping integrals, two groups of modes responsible for the formation of the central and circular beams of the second harmonic under the conditions of quasisynchronism were distinguished. It is found that, unlike homogeneous media, crystals with periodic polarization can be used for doubling the frequency of Bessel beams with cone angles changing in wide limits.     

Coherent Control of the Hartman Effect through a Photonic Crystal with Four-Level Defect Layer

In this paper, we examine the transmission of a probe field through a one dimensional photonic crystal (1DPC) when the sixth layer of the crystal is doped with four level atoms. We analyze effects of the external driving field on the passage of weak probe field across the photonic crystal. It is found that for the phase time delay of the probe photons, intensity of the driving field switches the Hartman effect from sub to superluminal character. It is interesting to note that in our model, the superluminal transmission of the probe pulse is accompanied by a negligibly small absorption of the incident beam. It ensures that the probe field does not attenuate while passing through the photonic crystal. A similar switching of the Hartman effect may be obtained by adjusting detuning of the probe field related to the excited states of the four-level doping atoms.     

表层厚度渐变一维耦合腔光子晶体的反射相位特性及其应用

利用传输矩阵法研究了表层厚度渐变的一维非对称耦合腔光子晶体的反射相位特性. 研究表明, 光子禁带内(包括缺陷模附近)的反射率在98%以上, 且基本不受表层厚度影响, 特别是, 在非正入射情况下, 简并的缺陷模随着表层厚度的变化会发生分裂; 进一步研究发现, 在缺陷模分裂处附近, TE, TM偏振的反射相位以及它们之间的相位差均敏感地依赖于表层厚度的变化, 从而使得反射光的偏振态也随表层厚度的变化而敏感变化, 其物理机理在于缺陷模分裂所造成的剧烈相位变化. 基于上述特性, 设计了一种表层厚度呈二维周期变化的一维光子晶体结构, 从该结构反射的激光经透镜聚焦后, 在聚焦区域同时存在各种偏振态(包括沿不同方向的线偏振、左旋或右旋圆偏振、椭圆偏振等)的子光束, 它们叠加后在聚焦区域将产生具有无规相位和无规偏振态的光场. 以上结果能有效降低激光的相干性, 在激光核聚变等领域有潜在的应用价值.     

Self-Diffraction of Bessel Light Beams in a Nonlinear Medium

The phenomenon of self-diffraction of Bessel light beams (BLB) in a nonlinear liquid medium has been studied experimentally and theoretically for the first time. Diffraction maxima which do not correspond to integer orders for an induced periodic structure have been registered. It has been shown that the appearance of these maxima is due to the initial BLB modulation, which can be caused by the departure of the axicon refracting surface from the ideal conical surface, as well as by the imperfection of the form of the Gaussian beam incident on the axicon.     

水下任意刚性散射体对Bessel波的散射特性分析

本文利用Bessel波的谐波展开式, 采用T矩阵方法的推导思路, 建立了水下任意刚性散射体在Bessel波照射下的声散射场计算公式. 以水下刚性椭球体和两端附连半球的刚性圆柱体为例, 计算了在不同波锥角β 下的反向散射形态函数, 同时, 依据镜反射波和绕行波的干涉物理模型, 给出了预报Bessel波照射下的反向散射形态函数峰峰间隔值的计算模型. 仿真结果表明本文提出的Bessel波照射下反向散射形态函数峰峰间隔值预报方法是准确有效的, 同时也说明, 本文建立的基于T矩阵法计算水下任意刚性散射体在Bessel波束下的声散射场方法是有效的, 这拓展了T矩阵法的应用领域.     

Generation of Bessel Beams at mm- and Sub mm-wavelengths by Binary Optical Elements

In this paper, binary optical elements (BOE’s) are designed for generating Bessel beams at mm- and sub mm- wavelengths. The design tool is to combine a genetic algorithm (GA) for global optimization with a two-dimension finite-difference time-domain (2-D FDTD) method for rigorous electromagnetic computation. The design process for converting a normally incident Gaussian beam into a Bessel beam is described in detail. Numerical results demonstrate that the designed BOE’s can not only successfully produce arbitrary order Bessel beams, but also have higher diffraction efficiencies when compared with amplitude holograms.     

Construct a polarizing beam splitter by an anisotropic metamaterial slab

We present a theoretical investigation of polarizing beam splitters based on an anisotropic metamaterial (AMM) slab. At the interface associated with a certain AMM, TE- and TM-polarized waves exhibit opposite amphoteric refraction characteristics, such that one polarized wave is positively refracted whereas the other is negatively refracted. The opposite amphoteric refractions result in a large birefringence in the AMM slab. By suitably using the large birefringence, we introduce a very simple and very efficient beam splitter to route the light. We show that the splitting angle and the splitting distance between TE- and TM-polarized beams is the function of anisotropic parameters, incident angle and slab thickness. PACS 41.20.Jb; 42.25.Gy; 78.20.Ci     

部分相干光对周期性局域空心光束的影响

用旋转毛玻璃和光阑把激光变成部分相干光, 再经过双轴棱锥系统把一束平行光变成两束同频率但不同径向波矢分量的无衍射贝塞尔光, 相干叠加产生了部分相干的周期性局域空心光束. 通过干涉理论与实验结果相互佐证, 得出局域空心光束的周期为2.5 mm. 进一步探究入射光场相干度对产生局域空心光束的影响, 发现随着相干度的降低局域空心光束中心暗斑与周围光强的衬比度会降低, 但不影响局域空心光束的周期以及中心暗斑尺寸.     

空心锥状双高斯光束传输特性研究

建立了空心锥状双高斯光束的模型.在空心高斯光束模型的基础上,由初始光场的光强分布,利用柱坐标下的柯林斯公式,导出了空心锥状双高斯光束经过傍轴光学系统的解析传输变换式由传输变换式计算分析了空心锥状双高斯光束在自由空问的可控传输特性,及在1,10和60 m的截面光环的光强分布.用KNbO3双轴晶体进行实验,获得了空心锥状双高斯光束,外锥折射的锥角等于入射光会聚角.实验表明,当空心光束处于锥状发射状态时,空心光束的光环内黑斑面积随传输距离的增加而增加,实验结果与模型吻合较好.该研究为进一步设计制备基于空心锥状舣高斯光束的新型激光元件提供了理论依据和设计参量.