Two Beam Collection Mode Photon Scanning Tunneling Microscope

We studied the image deformation due to the surface inclination of objects in photon scanning tunneling microscopes (PSTM). A novel collection mode PSTM with two light sources is proposed to reduce the deformation and experimental results show that the PSTM system is effective.     

原子力与光子扫描隧道组合显微镜

介绍了超高分辨光于扫描隧遭显微镜（PSTM）的计冗历程,为解决第一代（单光束照明）光千扫捕隧逼显傲镜中存在人为假象和样品光学图像与形貌图像难于分离两个难题,用“对称双光束照明方法消假象,用原子力与光子扫描隧道组合显微镜（AF／PSTM）图像分解方法分离样品光学透过率、折射率与形貌图像。研制成功新一代原子力与光子扫描隧道组合显微镜（AF／PSTM）样机。该样机在一次扫描中已获得两幅原子力显微镜图像（形貌与相位）和两幅光学图像（透过率和折射率）,有效地减少了假象,分解了样品光学折射率、透过率与形貌图像。     

镀纳米结构薄膜光纤探针的光子隧道扫描显微镜成像数值模拟

利用时域有限差分法,对镀纳米结构薄膜光纤探针的成像特性进行了三维数值模拟。在考虑光纤和样品相互作用的基础上,采用等效入射波法设置入射波和等高扫描。从成像分辨率和灵敏度的角度比较了不同纳米颗粒与样品间距、纳米颗粒大小、排列方式以及排列密度对成像的影响。结果表明,镀纳米结构薄膜光纤探针的光子隧道显微镜无论在制备的可行性上,还是在分辨率和灵敏度上都有显著的改进。     

Electromagnetic Invisibility of Elliptic Cylinder Cloaks

Structures with unique electromagnetic properties are designed based on the approach of spatial coordinate transformations of Maxwell's equations. Thisapproach is applied to scheme out invisible elliptic cylinder cloaks, which provide more feasibility for cloaking arbitrarily shaped objects. The transformation expressions for the anisotropic material parameters and the field distribution are derived. The cloaking performances of ideal and lossy elliptic cylinder cloaks are investigated by finite element simulations. It is found that the cloaking performance will degrade in the forward direction withincreasing loss.     

A Novel Method for Enhancing Goos-Hänchen Shift in Total Internal Reflection

Due to the tiny shift in order of optical wavelength for Goos-Hǎnchen （GH） shift, it is very difficult to directly measure and apply the GH shift. We develop a new method for enhancing GH shift of both TE and TM polarized waves. The method is based on a total reflection prism made of BK9 glass combined with a precise measurement of the resulting spatial displacement with a one-dimensional charge coupled device （CCD）. Measurements are performed to examine the validity of the method. Experimental and theoretical results indicate the feasibility of the method with an enhancement in optical wavelenghth shift at millimetre scale. The method is advantageous to application the GH shift in the optical domain, and is also meaningful for measuring even smaller changes in the refractive index of a liquid.     

探针尖带金属微粒的光子扫描隧道显微镜成像数值模拟

引入了色散介质的时域有限差分法散射场方程,并针对光子扫描隧道显微镜的带金属尖光纤扫描成像问题进行三维的数值模拟。在考虑了光纤和样品相互作用的情况下,采用等效入射波法设置入射波,探针扫描模式为等高扫描模式,从成像分辨力和灵敏度的角度,比较了不同入射角、不同的光纤一样品间距,不同金属类型,及不同金属尖大小的成像情况。数值模拟结果显示,带金属颗粒光纤探针尖的光子扫描隧道显微镜在成像分辨力和灵敏度上有显著的改进,而带不同类型金属颗粒情况下对分辨力影响不大,灵敏度是银最好。     

Rigorous electromagnetic analysis of dual-closed-surface microlens arrays

In this paper, we investigated the focal performance of the dual-closed-surface microlens arrays (DCSMAs) based on rigorous electromagnetic theory and boundary element method (BEM) in the case of TE polarization. The DCSMAs are designed with different substrate thickness and different distance between microlenses. DCSMAs designed according to different wavelengths are surveyed. The DCSMAs with different incident angles are also studied. Several focusing performance measures, such as the focal spot size, the focal position on the preset focal plane, the diffraction efficiency and the normalized transmitted power, are presented. Numerical results indicate the DCSMAs with different parameters can implement focusing beams and the focal performance of DCSMAs is easily influenced by the substrate thickness and the incident wavelength. Furthermore, the optimal thickness for the maximal diffraction efficiency of the DCSMAs is given. It is expected that the DCSMAs may be used as a parallel processing device in micro-optics systems.     

Two-Dimensional （2D） Polygonal Electromagnetic Cloaks

Transformation optics offers remarkable control over electromagnetic fields and opens an exciting gateway to design ＇invisible cloak devices＇ recently. We present an important class of two-dimensional （2D） cloaks with polygon geometries. Explicit expressions of transformed medium parameters are derived with their unique properties investigated. It is found that the elements of diagonalized permittivity tensors are always positive within an irregular polygon cloak besides one element diverges to plus infinity and the other two become zero at the inner boundary. At most positions, the principle axes of permittivity tensors do not align with position vectors. An irregular polygon cloak is designed and its invisibility to external electromagnetic waves is numerically verified. Since polygon cloaks can be tailored to resemble any objects, the transformation is finally generalized to the realization of 2D cloaks with arbitrary geometries.     

Fast calculation technique for scattering in T-matrix method

In scattering calculations using the T-matrix method, the calculation of the T-matrix involves multiplication and inversion of matrices. These two types of matrix operations are time-consuming, especially for the matrices with large size. Petrov et al. [D. Petrov, Y. Shkuratov, G. Videen, Opt. Lett. 32 (2007) 1168] proposed an optimized matrix inversion technique, which suggests the inversion of two matrices, each of which contains half the number of rows. This technique reduces time-consumption significantly. On the basis of this approach, we propose another fast calculation technique for scattering in the T-matrix method, which obtains the scattered fields through carrying out only the operations between matrices and the incident field coefficient. Numerical results show that this technique can decrease time-consumption by more than half that of the optimized matrix inversion technique by Petrov et al.     

光子扫描隧道显微镜的角谱传递函数

用傅里叶角谱衍理论推导了光子扫描隧道显笛镜的标量和矢量角谱传递函数。表明,光子扫描隧道显微镜的角谱传递鲜明地分成两个区,即远场区和近场区。随首探针榈间距增大,近场区内的角谱其振幅迅速衰减,频率越高衰减越快,而相位保持不变;相反远场区内的角谱内的角谱其振幅保持不变,而相位非均匀线性均匀线性增加,频率越低增加越快。光子扫描隧道显微镜对近场角谱的采集能力是其皮瑞利衍射极限的关键。坦 步根据角谱传递函数计     

Prevailing effects of interference or diffraction by multiple apertures

The effects of interference and diffraction produced by a bidimensional structure composed of multiple and identical apertures are studied. Such effects are competitive during the propagation, that is, in some planes the interference effects are more visible, while in others prevail the diffraction ones. Using the number of Fresnel zones, the spatial domains where the interference or diffraction effects prevail are defined and parameterized. Simulation and experimental results are further introduced to verify the proposed method.     

光子扫描隧道显微镜的进展

介绍我国第一台光子扫描隧道显微镜的研制情况，论述图像分解光子扫描隧道显微镜的原理和光子扫描隧显微的光存储技术的初步设想。     

Depolarization of multiply scattered light in transmission through a turbid medium with large particles

An approximate analytical method for solving the vector radiative transfer equation is proposed. The method is based on the assumption that single scattering of light by large-scale inhomogeneities occurs predominantly through small angles. The method is applied to calculate the polarization state of multiply scattered light. The results obtained are discussed for various turbid media.     

Surface plasmon mediated near-field imaging and optical addressing in nanoscience

We present an overview of recent progress in "plasmonics". We focus our study on the observation and excitation of surface plasmon polaritons (SPPs) with optical near-field microscopy. We discuss in particular recent applications of photon scanning tunnelling microscope (PSTM) for imaging of SPP propagating in metal and dielectric wave guides. We show how near-field scanning optical microscopy (NSOM) can be used to optically and actively address remote nano objects such as quantum dots. Additionally we compare results obtained with near-field microcopy to those obtained with other optical far-field methods of analysis such as leakage radiation microscopy (LRM).     

Near-field effect in two-atom system

The self-consistent problem is solved for the interaction of two dipole atoms situated at arbitrary distance from one another with the field of quasiresonant light wave. Atoms are considered to be linear Lorenz oscillators. Polarizing fields inside the system include both Coulomb and retarding parts. The solutions obtained are investigated for the case when atoms have the same polarizabilities and interatomic distance is much less than external light wavelength. Formulas for electric fields inside and outside of small object are obtained. It is shown that longitudinal and transverse optical oscillations are possible to exist inside small two-atom object. Dispersion laws of these oscillations depend upon interatomic distance and upon angle between axis of the system and the direction of propagation of external wave. The field outside the small object in wave zone is linearly polarized with the choice of linear polarization of external field. However, the directions of polarization of these waves are different and depend essentially upon frequency. The amplitude of field outside small object in wave zone is shown to depend essentially on the frequency of external field and interatomic distance. The results obtained are treated as near-field effect in the optics of small objects making it possible to investigate the structure of small objects with optical radiation. Received 26 October 1998 and Received in final form 26 January 2000     

Analytical Model of Doppler Spectra of Light Backscattered from Rotating Convex Bodies of Revolution in the Global Cartesian Coordinate System

We present an analytical model of Doppler spectra in backscattering from arbitrary rough convex bodies of revolution rotating around their axes in the global Cartesian coordinate system. This analytical model is applied to analyse Doppler spectra in backseatter from two cones and two cylinders, as well as two ellipsoids of revolution. We numerically analyse the influences of attitude and geometry size of objects on Doppler spectra. The analytical model can give contribution of the surface roughness, attitude and geometry size of convex bodies of revolution to Doppler spectra and may contribute to laser Doppler velocimetry as well as ladar applications.     

Hybrid Lifting Wavelet-Like Transform for Solution of Electromagnetic Integral Equation

A hybrid lifting wavelet-like transform scheme is successfully applied to the solution of electric field integral equation using Rao-Wilton-Glisson basis functions. To speed up the matrix transform process, the lifting scheme is adopted. Numerical examples of different three-dimensional perfectly electric conducting objects are considered. Compared with the method of moments, the proposed matrix transform scheme can save considerable CPU time and memory.     

Coherent effects of multiple scattering for scalar and electromagnetic fields: Monte-Carlo simulation and Milne-like solutions

Based on an expansion of the Bethe-Salpeter equation in scattering orders a semi-analytic approach for simulation of coherent phenomena of multiple scattering in random media has been developed. We found that for scalar field the manifestation of these phenomena, observed as temporal field correlation function and coherent backscattering, are universal and well agreed with the results predicted by diffusion approximation. For the electromagnetic field the temporal correlation function and coherent backscattering are noticeably differ from those found for the scalar field, depending strongly on the scattering anisotropy. The obtained numerical results, for the first time to our knowledge, are compared directly with the known generalizations of the Milne solution.     

Temperature Influence on Divergence Angles of Quartz Crystal Wollaston Prism

We propose a structural angle and main refractive indices as two key factors to understand the temperature influence on the divergence angles of the Wollaston prism. The temperature influence on the divergence angles of quartz crystal Wollaston prism is studied theoretically. The results show that divergence angles decrease with increasing temperature, while the divergence angle of e-light decrease more quickly than that of o-light. The testing system is established to verify the above results, and the experimental results are in agreement well with the theoretical analysis.     

A Simple Model for Measuring Refractive Index of a Liquid Based upon Fresnel Equations

Due to many experimental data required and a lot of calculations involved, it is very complex and cumbersome to model prism-based liquid-refractive-index-measuring methods. We develop a new method of mathematical modelling for measuring refractive index of a liquid based upon the Fresnel formula and prism internal reflection at an incident angle less than the critical angle. With this method, only two different concentrations measurements for a kind of solution can lead to the determination of computational model. Measurements are performed to examine the validity of the theoretical model. Experimental results indicate the feasibility of the theoretical model with an error of 1%. The method is also capable of measuring even smaller changes in the optical refractive index of the material on a metal surface by the surface plasma resonance sensing techniques.