Statistical Parameters for Characterizing the Indicating Surface of Natural Reflectance in Absorbing Uniaxial Media

Abstract

The indicating surface of natural reflectance for absorbing uniaxial media is studied in this paper. Expressions for the maximum, minimum, mode and median of the distributions of natural reflectances have been obtained. In order to obtain accurate values of the mean natural reflectance and its standard deviation, it is necessary to resort to numerical methods. When, in the expression of the mean natural reflectance corresponding to transparent media, the real refractive index is replaced by the complex one, these expressions are also valid for the particular case of weakly absorbing media. To obtain accurate values for the standard deviation, it is also necessary to resort to numerical methods. The values calculated for several theoretical cases and for five minerals—in air and in oil—are compared with those obtained using a simulation method, and both sets of results are in good agreement.     

A Method for the Optical Characterization of Thin Uniaxial Samples

An optical characterization procedure for small fragments of uniaxial materials is described involving the simple use of crossed polarizers with one polished face of the material. The reflectance at a fluid-uniaxial slab boundary beyond, but near, the critical angle of incident light is examined for linear incidence polarization using an orthogonal output polarizer. It is found that, as the crossed incident and output polarizers are rotated together, there are, for a given angle of incidence, particular polarization angles for which the reflectivity is a minimum. These angles give information on the optical tensor of the crystal under study. Further the intensity of the reflected light, for incidence angles beyond critical with the input and output polarizers crossed, has as a function of the incident polarization angle an oscillatory form which, when fitted to theory, can also yield the full uniaxial tensor of the material under study. This is confirmed experimentally for a thin single crystal of calcite with one polished face.     

一种测量光学滤波器参数的低相干方法

在光纤通信网络中, 以微环为代表的光学滤波器是实现在波长频段选择功能的重要器件。测量该器件的物理参数不仅是实际应用的需求更有利于设计更加复杂的滤波器结构。本文基于低相干干涉测量技术, 给出一种通用数学方法, 可获得复杂结构微环滤波器的物理参数。该方法引入数字滤波器概念以及 Z变换分析法来对光学滤波器进行建模, 并用简洁的线性方程组将干涉图中峰值以及传输函数的系数关联起来。对于一个给定的滤波器结构, 根据传输函数与物理参数的内在关联, 物理参数就能被准确地计算出来, 从而为器件的激光修正提供关键参数。实验结果表明, 该方法实现了低成本并且准确可行。     

A Simple Procedure for the Estimation of Local Stress Intensity Factors for Semi-Elliptical Surface Cracks

Stress intensity factor solutions are available for semi-elliptical surface cracks under different stress distributions. But in most cases, only the two values at the deepest point and at the surface points are reported. A simple method is proposed, which allows the stress intensity factor to be estimated at other points of the crack front as well. This revised version was published online in July 2006 with corrections to the Cover Date.     

Unified Measurements of Quantities Characterizing Incoherent Optical Radiation

A suite of state primary standards is described for the units of optical radiation consisting of precision standard sources, detectors, and other opticoelectronic devices developed at VNIIOFI in the period 1982–2002. Results are given from international comparisons and the use of standard facilities and calibration units for metrological support to space research and remote Earth sensing. __________ Translated from Izmeritel'naya Tekhnika, No. 11, pp. 12–16, November, 2005.     

A Simple Route to Fabricate Percolated Perpendicular Magnetic Recording Media

A simple approach is proposed for fabrication of percolated perpendicular media (PPM). Nano pore array with pore diameter of 12-15 nm and different pore densities has been prepared by anodizing aluminum on silicon wafers. The pore density increases from 3.2times10¹⁰ cm^-2 to 11.0times10¹⁰ cm^-2 with the decrease in anodizing voltage from 30 to 10 V. Then, Pt (7 nm)/{Co (0.5 nm)/Pt (2) nm}₅ multilayers are deposited onto this porous anodized alumina (AAO) by sputtering. The pore size is reduced to 10-12 nm after deposition of magnetic layers. The Co/Pt multilayers on AAO exhibit perpendicular magnetic anisotropy, squareness ratios of unity, and negative nucleation fields. The perpendicular coercivity increases linearly with the increase in pore density due to the pinning effect imposed by the pores, which is consistent with theoretical calculation for PPM     

TeOx Thin Films for Write-Once Optical Recording Media

TeOx thin films were prepared by vacuum evaporation of TeO2 powder. Structural characteristic and surface mor-phology of the as-deposited films was analyzed by using X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffractometer and atomic force microscopy. It was found that the films represented a two component system comprising Te particies dispersed in an amorphous TeO2 matrix. The dispersed Te particies were in a crystalline state. The TeOx films showed a finely granular structure and a rough surface. Results of the statie recording test showed that the TeOx films had good writing sensitivity for short-wavelength laser beam (514.5 nm). Primary results of the dynamic test at 514.5 nm were also reported. The TeOx films were suitable for using as a blue-green wavelength high density optical storage medium.     

A Simple Optical Reader for Upconverting Phosphor Particles Captured on Lateral Flow Strip

A simple optical reader was developed for rapid and sensitive quantification of lateral flow (LF) strip with upconverting phosphor (UCP) particles as reporters. The excitation beam from a 980 nm laser diode (LD) was focused to a 4 mm (length) $,times,$0.02 mm (width) rectangular spot on LF strip. A rectangular slit with 4 mm $,times,$0.02 mm before the photomultiplier tube (PMT) which was selected as receiver was introduced as field diaphragm to prevent stray light from entering the PMT. The scanning resolution was 20 $mu$m, and the scanning speed was 0.75 mm/s, and the scanning range was 10 mm. With the above optical reader, serial dilutions of Yersinia pestis F1 antigen were detected to achieve the test sensitivity was 5 ng/ml, and the dynamic range reached 150 ng/ml. The algorithms of the low-pass filter and the first derivative were used to search the boundaries of T line and C line from the original data acquired by the reader. A four-parameter logistic mathematical model was used to deduce the quantitative equation for determination of unknown F1 antigen concentration. Our 1-D optical reader possessed the following characteristics: high 1-D testing resolution, high sensitivity, simple structure, simple data processing method, high testing efficiency, and small total volume.      

A Biaxial Fatigue Specimen for Uniaxial Loading

Abstract: The aim of this paper is to present a novel un‐notched fatigue test specimen in which a biaxial stress state is achieved using a uniaxial loading condition. This allows the problem of multi‐axial fatigue to be studied using relatively common one‐axis servo‐hydraulic testing machines. In addition the specimen presented here is very compact and can be made using a small volume of material (100 × 40 × 4.5 mm). For this specimen, the degree of biaxiality, defined by the parameter is equal to approximately 0.45. The specimen geometry was optimised using the Dang Van multi‐axial fatigue criterion. In addition to use as a fatigue specimen, it has been demonstrated that the biaxial specimen presented here is also suitable for biaxial tensile tests, to determine the rupture strength of a material in a biaxial stress state. Two different materials have been investigated: The first was wrought aluminium 2024‐O in the form of 5 mm sheets. The second was a cast aluminium‐silicon alloy AlSi7Cu0.5Mg0.3, commonly used in automotive and aeronautical applications. The fatigue strengths were determined at 2 × 10⁶ cycles and at various R‐ratios using a staircase procedure. For the aluminium 2024, it is shown that the biaxial stress state increases the maximum permissible first principal stress when compared to the uniaxial condition. However, in terms of the cast aluminium alloy, it has been demonstrated that this type of fatigue specimen is not suitable for materials containing casting defects, in particular micro‐shrinkage pores, because the volume of material, in which the stress state is biaxial, is not large enough.     

摄影经纬仪胶片简易自动判读的实现

为了使测量站在日常维护中能够通过数据判定摄影经纬仪设备性能 ,提出了利用扫描仪扫描胶片 ,形成位图文件 ,结合图像处理技术 ,准确读出各项测量数据。文中着重论述了图像的二值化预处理和利用相关法判读脱靶量     

Critical Edge Characterization of the Optical Tensor of a Uniaxial Crystal

Abstract

The angle dependent reflectivity at the boundary between a uniaxial crystal and an isotropic fluid, which has a refractive index greater than the smaller index of the uniaxial material but less than the other index, is analysed extensively. Consequently the use of a prism and matching fluid with just such refractive indices allows a procedure for the complete characterization of a uniaxial medium to be established. This is undertaken by studying the reflectivity at the prism/fluid/crystal interface with an angle of incidence near to the pseudo-critical angle of the lower index in the uniaxial crystal and examining how the reflectivity varies with the rotation of the uniaxial crystal. Experimental results using a single crystal of calcite give very good agreement with the analysis and computer modelling of this situation and illustrates the use of the new technique.     

A Method of Forming Optical Diffusers of Simple Known Statistical Properties

A method is described by which optical diffusing surfaces may be formed using photoresist materials. These surfaces have a surface profile which is smoothly modulated and thus amenable to theoretical modelling. The distribution of surface heights in the surfaces has been determined using an interferometric method. Typical results are given, together with comparisons with both the expected (gamma function) and desired (gaussian) forms of distribution.     

无序光学介质中的光子局域化

光子局域化是凝聚态物理学中电子局域化的光子学类比。概述了无序光学介质中光子局域化的理论基础及其研究内容,介绍了几个重要的观察强光子局域化现象的实验。我们相信光子局域化材料会有广泛的应用前景。     

一个表征非晶形成能力的新参数

基于文献数据的统计分析,获得了非晶形成能力新参数的表达式ζ=Tg/(Tl-Tx)a.Tx-Tg/(Tl)b。用线性回归方法推导出形成非晶合金的临界尺寸Dmax与ζ的经验公式为Dmax/mm=(1.061±0.067)ζ+(2.490±0.325)。与其他判据相比,这两个公式更加可靠,适用于多种合金体系。     

Brillouin Diagrams for Optical Wave Propagation in Twisted Dielectric Media

Light propagation in an inhomogeneous, anisotropic medium is discussed. The medium shows the most general anisotropy (optically biaxial) and a special kind of inhomogeneity: rotation of a principal axis of the dielectric tensor about the z-axis. Since the analytic treatment is very troublesome, we use group theory to deduce qualitative statements on frequency splitting in the Brillouin diagram. As in all periodic anisotropic media, where two different group velocities exist, an infinite number of stop bands is produced by a splitting into maximally three stop bands at each point of interaction. Two special cases for the dielectric tensor are treated also: optically biaxial media with one axis in the z -direction and optically uniaxial media with an oblique optical axis. The group theory required is similar to the theory of crystallographic double space groups.     

Parity-Time Symmetry in Non-Hermitian Complex Optical Media

The exploration of quantum-inspired symmetries in optical and photonic systems has witnessed immense research interest both fundamentally and technologically in a wide range of subject areas in physics and engineering. One of the principal emerging fields in this context is non-Hermitian physics based on parity-time symmetry, originally proposed in the studies pertaining to quantum mechanics and quantum field theory and recently ramified into a diverse set of areas, particularly in optics and photonics. The intriguing physical effects enabled by non-Hermitian physics and PT symmetry have enhanced significant application prospects and engineering of novel materials. In addition, there has been increasing research interest in many emerging directions beyond optics and photonics. Here, the state-of-the art developments in the field of complex non-Hermitian physics based on PT symmetry in various physical settings are brought together, and key concepts, a background, and a detailed perspective on new emerging directions are described. It can be anticipated that this trendy field of interest will be indispensable in providing new perspectives in maneuvering the flow of light in the diverse physical platforms in optics, photonics, condensed matter, optoelectronics, and beyond, and will offer distinctive application prospects in novel functional materials.     

An Approximate Linear Relationship for the Optical Response of Turbid Media

The optical response of a homogeneous turbid medium is often expressed analytically with the aid of the simplified theory of Kubelka and Munk. The equations derived from this theory yield the response A as an explicit function of absorption Kand scatter S. In practice, however, an inverted form is frequently needed, which would display absorption as an explicit function of A and S. No closed-form rigorous inversion of the response function A(S, K) is available, though approximate solutions exist. All direct inversions, analytical or empirical, are highly non-linear, even though for measurement and instrumentation purposes a linear characteristic is highly desirable. This paper shows that this can be achieved by using a logarithmic transform for the transmittance and a reciprocal one for the reflectance mode. Graphs are given for the coefficients of the linear approximation applicable over a wide range of the parameters S and K ; also shown is the mean error incurred in this range; it is nowhere in excess of a few per cent. The values displayed were obtained numerically using the least-square method of linear approximation. It is expected that the linearized form will be useful in many areas of applied densitometry. The advantages should apply not only to instrument design and measurement procedures, but also to theoretical studies aimed at practical situations.     

运用ASAP光学软件模拟单轴晶体的锥光干涉

为了模拟不同光轴取向、光束发散角、晶体厚度或入射波长等参数下的单轴晶体锥光干涉,在 ASAP中定义起偏器、晶体、检偏器和接收屏的几何形状和光学特性,产生一组锥状高斯光束并设置其相干性和波动性,进行光线追迹、计算并显示接收屏上的干涉场能量分布。所得模拟结果表明,光轴与晶体表面垂直时,干涉条纹是 1组以光轴为圆心且被十字分割的内疏外密、明暗相间的同心圆环;平行时,是 2组分别以光轴的平行和垂直方向为对称轴的、内疏外密、明暗相间的双曲线;既不垂直也不平行时,条纹特征因光轴取向而异;当增大发散角、晶体厚度或减小波长时,干涉条纹都向内移动且条纹数增多,反之亦然;起、检偏器正交时的干涉条纹都和它们平行时的条纹互补。