大气气溶胶消光特性和折射率的测量

 介绍了一种综合利用能见度仪、微脉冲激光雷达和光学粒子计数器测量大气气溶胶折射率的新方法。首先使用能见度仪和激光雷达测量出大气气溶胶的消光系数和消光后向散射比,然后使用粒子计数器测量出粒子谱分布,结合气溶胶粒子折射率,根据球形粒子的米（Mie）散射理论,可以得到气溶胶消光系数和消光后向散射比。通过分析消光系数、消光后向散射比、粒子谱分布和折射率之间的关系,结合已知的消光系数和消光后向散射比,反演出大气气溶胶粒子的折射率。     

基底和膜层-基底系统的赝布儒斯特角计算(英文)

对基底和膜层-基底系统的赝布儒斯特角进行了数值计算.结果显示:当基底的消光系数小于0.01时,基底的赝布儒斯特角主要是由折射率决定;当基底的消光系数大于0.1时,基底的赝布儒斯特角不仅与折射率有关,而且还与消光系数有关,随着消光系数发生后周期性变化.研究表明:单层膜-基底系统的赝布儒斯特角主要由膜层的物理厚度、折射率、基底的光学常量所决定;在HfO2-硅和HfO2-融石英基底系统中,赝布儒斯特角随着入射光波长和膜层厚度的变化呈现准周期性规律变化,可能是由入射光在膜层的干涉效应引起的.     

Generalized implicit-summation technique for multiquantum processes in systems containing continua

Summary Implicit-summation technique has been so far limited to the lowest-order term of the amplitude for multiphoton ionization. In this paper, a previosly derived result in which the higher-order terms are taken into account is considered. The implicit-summation technique is adapted for the treatment of the complete amplitude, resulting in a new set of differential equations. The solution procedure for this set of differential equations is discussed.

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Riassunto La tecnica di somma implicita è stata fino ad ora limitata al termine d'ordine piú basso dell'ampiezza per la ionizzazione multifotonica. In questo lavoro si considera un risultato derivato in precedenza nel quale termini di ordine piú alto sono presi in considerazione. La tecnica di somma implicita è adattata al trattamento dell'ampiezza completa, che risulta in una nuova serie di equazioni differenziali. Si discute la procedura di soluzione per questo gruppo di equazioni differenziali.

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Резюме Техника неявного суммирования до сих пор применялась к члену низшего порядка для амплитуды многофотонной В этой статье рассматривается ранее полученный результат, в котором учитываются члены более высоких порядков. Техника неявного сммирования применяется для рассмотрения полной амплитуды, получается новая система дифференцальных уравнений. Обсуждается процедура решемия этой системы дифференциальных уравнений.

     

特种工程塑料太赫兹光学参数测量及误差分析

以聚苯硫醚(PPS)、聚醚酰亚胺(PEI)及其玻璃纤维增强材料(PPS-GF30,PEI-GF30)为样品,获得了在太赫兹频段的光谱特性。首先,利用太赫兹时域光谱系统,在透射模式下,测试了四种材料在自由空间的时域信号。然后,根据提取光学参数的物理模型及菲涅尔透射公式计算材料的折射率及消光系数,同时对物理模型和菲涅耳公式解析法仿真,保障了实验测试和算法的合理性与可靠性。最后,依据误差传输理论计算了由主要因素决定的光学参数误差。在样品各自的太赫兹有效频段,实验显示： PPS： n=1.889~1.945(误差0.003~0.012),κ=0.001~0.047、(误差0.000 1~0.002 6),PPS-GF30： n=1.654~1.672(误差0.003~0.004),κ=0.002~0.057(误差0.000 1~0.002 8),PEI： n=1.713~1.733(误差0.002~0.012),κ=0.005~0.035(误差0.000 1~0.003 0),PEI-GF30： n=1.688~1.732(误差0.003~0.004),κ=0.036~0.068(误差0.000 2~0.002 6)。结果表明： 作为太赫兹超材料器件的基底,PPS适合低频,PEI适合高频,玻璃纤维增强的PPS,PEI相比纯样品,不仅力学性能得到改善,并有利于信号探测,而且在有效频段的高频部分,探测灵敏度更强。研究提供了PPS,PEI及其玻璃纤维增强材料在太赫兹频段的基础参数,为太赫兹领域超材料器件的研究提供了重要参考。     

Conformal symmetry of classical electromagnetic zero-point radiation

The two-point correlation functions of classical electromagnetic zero-point radiation fields are evaluated in four-vector notation. The manifestly Lorentz-covariant expressions are then shown to be invariant under scale transformations and under the conformal transformations of Bateman and Cunningham. As a preliminary to the electromagnetic work, analogous results are obtained for a scalar Gaussian random classical field with a Lorentz-invariant spectrum.     

纤锌矿GaN薄膜光学性质的研究

在测试大量纤锌矿GaN外延薄膜透射光谱基础上,通过对有代表性的四个样品的透射光谱进行拟合,获取了GaN外延薄膜的光学常量并计算了薄膜厚度.结果表明:GaN外延薄膜的折射率差异较小,但在370～800 nm波长范围内消光系数差异很大,GaN薄膜的消光系数差异在一定程度上可用以评价外延薄膜的质量.     

Polaron effects on the refractive index changes in cylindrical quantum dots with parabolic potential

The effect of electron-LO-phonon interaction on refractive index changes (RICs) for cylindrical quantum dots (CQDs) with an applied electric field is theoretically investigated. Analytic forms of the linear and third-order nonlinear the RICs are obtained for a cylindrical QD by using compact-density-matrix approach and iterative method, and the numerical results are presented for a GaAs cylinder quantum dot. The results show that the RICs coefficient is greatly enhanced and the peak shift to the aspect of high energy when considering the influence of electron-LO-phonon interaction.     

Absorption of electromagnetic radiation by a cylindrical metal particle

The cross section of the absorption of electromagnetic radiation by a cylindrical metal particle is calculated. The calculation is performed in the low-frequency limit, in which the contribution of eddy currents to the absorption dominates, and for comparatively small particles (with radii of ≈10 nm), which allows us to neglect the skin effect. The case when the mean free path of electrons in the metal bulk substantially exceeds the radius of the cylindrical particle is considered in detail. The specific absorption cross sections for spherical and cylindrical particles are compared.     

Calculation of the absorption coefficients of optical materials by measuring the transmissivities and refractive indices

In this paper, a formula for accurate calculation of the absorption coefficient of optical material is deduced by the relationship of its transmissivity, refractive index and absorption coefficient. Because the values of transmissivity and refractive index of the optical material with a higher accuracy can be determined by the instruments or obtained directly from the references, the calculated results of the absorption coefficients with a higher accuracy is certified. The absorption coefficients of some optical materials are calculated with it, and the results are discussed.     

Effects of symmetry breaking in finite quantum systems

The review considers the peculiarities of symmetry breaking and symmetry transformations and the related physical effects in finite quantum systems. Some types of symmetry in finite systems can be broken only asymptotically. However, with a sufficiently large number of particles, crossover transitions become sharp, so that symmetry breaking happens similarly to that in macroscopic systems. This concerns, in particular, global gauge symmetry breaking, related to Bose–Einstein condensation and superconductivity, or isotropy breaking, related to the generation of quantum vortices, and the stratification in multicomponent mixtures. A special type of symmetry transformation, characteristic only for finite systems, is the change of shape symmetry. These phenomena are illustrated by the examples of several typical mesoscopic systems, such as trapped atoms, quantum dots, atomic nuclei, and metallic grains. The specific features of the review are: (i) the emphasis on the peculiarities of the symmetry breaking in finite mesoscopic systems; (ii) the analysis of common properties of physically different finite quantum systems; (iii) the manifestations of symmetry breaking in the spectra of collective excitations in finite quantum systems. The analysis of these features allows for the better understanding of the intimate relation between the type of symmetry and other physical properties of quantum systems. This also makes it possible to predict new effects by employing the analogies between finite quantum systems of different physical nature.     

Special features of absorption of electromagnetic radiation by a cylindrical particle

The cross section of electromagnetic radiation absorption by a cylindrical metal particle was calculated. No limitations were imposed on the relation between the electron mean free path and the particle size. Specific absorption cross sections of cylindrical and spherical particles are compared. The results of the numerical calculation are presented graphically.     

Interaction of electromagnetic radiation with a cylindrical particle of finite length

The magnetic absorption cross section of a cylindrical metal particle of finite length is calculated. A general case is considered when the ratio of the transversal dimension of a particle to its length may take arbitrary values. Diffuse reflection of electrons from the internal surface of a particle is chosen as the boundary condition for the problem. Limiting cases are considered, and the results are discussed.     

Visualization and interferometry for cylindrical and spherical sample tomography and profilometry

A technique combining image processing and laser interferometry for visualizing and detecting the deformation of transparent cylindrical and spherical sample is proposed. This deformation includes geometric deformation such as volume transition in profilometry and physical deformation such as refractive index change in tomography. Phase contour lines are used for quantitative analysis and graphical representation of the deformation. This method allows us to visually detect the spatial variation of the deformation field and to evaluate the test quality such as misalignment of optical system. A theoretical analysis using phase contour map to characterize the deformation field is described in detail. A method using phase contour map to qualify the interferometric test is proposed. Analysis of test examples is carried out. Suggestions on using phase contour line method to ameliorate test system design are finally discussed.     

Confinement from spontaneous breaking of scale symmetry

We show that one can obtain naturally the confinement of static charges from the spontaneous symmetry breaking of scale invariance in a gauge theory. At the classical level a confining force is obtained and at the quantum level, using a gauge invariant but path-dependent variables formalism, the Cornell confining potential is explicitly obtained. Our procedure answers completely to the requirements by 't Hooft for “perturbative confinement”.     

真皮革和人工革在太赫兹波段的光谱研究

皮革检测鉴定的市场需求缺口巨大,不同种类皮革,尤其是不同种类真皮革无损、无标记检测具有重要的应用价值。利用太赫兹时域光谱技术系统地测试了不同种类真皮革和人工革的太赫兹透射光谱,计算了不同真皮革和人工革的太赫兹吸收系数和折射率。在0.2~1.5 THz范围内,不同种类皮革的太赫兹吸收系数和折射率数值大小具有明显差异,真皮革大于人工革;且真皮革中,爬行类皮革>鱼类皮革>哺乳类皮革。进一步地,猪、牛、羊真皮革在25~80 ℃加热过程中太赫兹时域光谱振幅变化均在60 ℃左右出现拐点,而人工革无拐点;且猪、牛、羊真皮革变化趋势各异。为了验证皮革太赫兹光谱产生差异的原因,首先对代表性皮革牛皮革、人造革和合成革的主要组成成分牛皮胶原蛋白、聚氯乙烯（PVC）和聚氨酯（PU）进行了太赫兹光谱测试,牛皮胶原蛋白的太赫兹吸收系数和折射率大于聚氯乙烯和聚氨酯;并且在25~80 ℃加热过程中胶原蛋白出现变化拐点,而聚氯乙烯无。实验结果显示,皮革主要组成成分的太赫兹光谱特征的数值差异和变化趋势与对应皮革相同,表明不同种类皮革间差异性的太赫兹光谱特征主要来源于其组成成分的不同。基于此,太赫兹光谱技术有望用于皮革的快速、准确、无损、无标记检测,用于区分不同种类真皮革和人工革,尤其是分辨来源于爬行动物、哺乳动物和鱼类的真皮革。     

Absorption of electromagnetic radiation in systems with orientational interactions

Absorption of electromagnetic radiation in ordered ferroelectric and antiferro-electric systems in external electrical fields has been investigated by means of Monte Carlo method. The dependences of the areas of the hysteresis curves on the frequency of the field have been calculated. At the resonance frequency, there is a maximum of the area of the hysteresis curve; the position of this maximum depends weakly on the temperature and the constant of intra- and interchain inte-ractions, and its height increases with decreasing temperature and increasing the interaction energy between molecules.     

Transition radiation of surface electromagnetic waves by electron bunches in a cylindrical waveguide

Transition surface electromagnetic radiation from electron bunches that cross a metal-insulator-semiconductor structure in a perfectly conducting semi-infinite cylindrical waveguide is studied. It is shown that, using a periodic sequence (train) of electron bunches, a particular surface waveguide eigenmode can be amplified by bringing its frequency to resonance with the bunch repetition frequency in the train. Those eigenmodes are amplified most efficiently whose frequency falls into the range occupied by the first maximum of the geometric factor of one bunch.     

Absorption of electromagnetic radiation by a bimetallic cylindrical particle of finite length

The absorption cross section of electromagnetic radiation is calculated for a bimetallic cylindrical particle of finite length. A general case is considered, where the ratio of the radius of the particle core to the particle radius and the ratio of the radius of the particle to its length can take arbitrary values. The conditions of diffuse reflection of electrons from the internal and external surfaces of the metal shell of the particle and from its faces are used as the boundary conditions of the problem. The effect of the ratio of the radius of the core of a bimetallic cylindrical particle to the particle radius and the ratio of the radius of the particle to its length on the electromagnetic properties of the particle is analyzed.