Determining the retardation of a wave plate by using spectroscopic method

A method for determining the retardation of a wave plate is presented. The method is based on polychromatic polarization interference technique. Through accurate judgment of the intersection points' wavelengths of the two orthogonal polarization transmittance spectrum curves, the apparent retardation, the absolute retardation values and the physical thickness of a wave plate can be measured at a wide spectral range from 400 nm to 800 nm. Experimental results show that the proposed method has very high precision. In addition, the method has a significant advantage that has high misalignment tolerance. The method reported here should have applications in fabrication and measurement of a wave plate.     

A high-precision optical metrology system for determining the thickness of birefringent wave plates

This study develops a non-destructive measurement system for determining the thickness and refractive indices of birefringent optical wave plates. Compared to previous methods presented in the literature, the proposed metrology system provides the ability to measure the thickness of the birefringent optical plate in high-precision. The results show that for a commercially available birefringent optical wave plate with refractive indices of n_e=1.5518, n₀=1.5427 and a thickness of 452.1428 μm, the experimentally determined value for the error in the wave plate thickness measurement is just 0.046 μm. The measurement resolution of the proposed system exceeds that of the interferometer hardware itself. The proposed method provides a simple yet highly accurate means of measuring the principal optical parameters of birefringent glass wave plates.     

A spectroscopic method of determining the isotopic composition of magnesium

The composition is determined from the isotopic shift of the Mgl 880.68 nm line. The coefficient of variation for magnesium metal is 1.8%, but 4% for magnesium oxide. Several spectroscopic analyses can be performed in the time needed for one mass-spectrometer analysis, which reduces the error of analysis by a factor two or three.We are indebted to Professor A.N. Zaidel for valuable advice and to N. A. Novozhilova for assistance with the measurements.     

A Wavelet-Based Processing method for simultaneously determining ultrasonic velocity and material thickness

Methods of measuring ultrasonic wave velocity in an elastic sample require data on the thickness of the sample and/or the distances between the transducers and the sample. The uncertainty of the ultrasonic wave velocity measurements generally depends on that of the data available. Conversely, to determine the thickness of a material, it is necessary to have a priori information about the wave velocity. This problem is particularly hard to solve when measuring the parameters of biological specimens such as bones having a greater acoustical impedance contrast (typically 3-5 MRayl) than that of the surrounding soft tissues (typically 1.5 MRayl). Measurements of this kind cannot easily be performed. But obtaining the thickness of a bone structure and/or the ultrasonic wave velocity is a important problem, for example, in biomechanical field for the calculation of elastic modulus, or in acoustical imaging field to parameterize the images, and to reference the grey or color level set to a physical parameter.The aim of the present study was to develop a method of simultaneously and independently determining the velocity of an ultrasonic wave in an elastic sample and the wave path across the thickness of this sample, using only one acquisition in pure transmission mode. The new method, which we have called the “Wavelet-Based Processing” method, is based on the wavelet decomposition of the signals and on a suitable transmitted incident wave correlated with the experimental device, and the mathematical properties such as orthonormality, of which lend themselves well to the time-scale approach. By following an adapted algorithm, ultrasonic wave velocities in parallelepipedic plates of elastic manufactured material and the apparent thicknesses were both measured using a water tank, a mechanical device and a matched pair of 1 MHz ultrasonic focused transducers having a diameter of 3 mm, a focal length of 150 mm and beam width of 2 × 2 mm at the focus (mean temperature 22°). The results were compared with those obtained with a conventional Pulse-mode method and with the control values, to check their validity. Measurements performed on bovine and human dry cortical bone samples are also presented to assess the limitations of the method when it is applied to elastic biological samples, including those of an equal-wavelength size (≈1.5 mm). The thicknesses and the ultrasonic wave velocities were then measured in this kind of (quasi-) parallelepipedic elastic materials with an mean estimated error ranged from 1% to 3.5% compared to the referenced values.     

一种测量波片相位延迟的简易方法

本文提出了一种精确测量波片相位延迟量的简易方法。在塞纳蒙补偿器中,只需测量检偏器在四个不同方位角时的相应光强,就可精确获得波片的相位延迟量。     

色编码板参量确定的实验方法

给出了通过实验确定色编码板参量的方法，该方法原理简单，制作方便，实用性强。     

New method for determining refractive index and thickness of fluorescent thin films

The optical parameters of homogeneous, isotropic, and fluorescent thin films are determined by comparing measured with calculated angular intensity distributions of the s- and p-polarized light emitted into the substrate. The method also yields information about the multipole nature of the emitted radiation. The theory is presented for electric and magnetic dipole transitions. For extremely thin layers of optical thickness n₀d₀ ? λ/8 (where λ is the emission wavelength) analytic expressions for the angular intensity distributions are given. For between 25–30 nm thick evaporated layers of an europium-benzoyltrifluoro-acetone- chelate the refractive index was determined to be n₀ = 1.57 at λ = 612 nm. The fluorescent light emitted by these layers in an about 6 nm wide band centered at λ = 612 nm is emitted by randomly oriented electric dipoles.     

Combined spectroscopic method for determining the fluorophore concentration in highly scattering media

The spectroscopic analysis of composition of highly scattering media, in particular, biological tissues, is associated with difficult interpretation of the spectrum of radiation subjected to both absorption and multiple scattering in a medium. The proposed technique of the combined analysis of spectra of laser radiation fluorescence and diffuse reflection by highly scattering biological media allows quantitative determination of concentrations of basic chromophores and fluorophores in tissues with simultaneous estimation of structural changes in objects under study. To determine the effect of structural parameters on the intensity of backscattered laser and fluorescent radiation, numerical simulation and physical modeling of the interaction of exciting and fluorescent radiation with highly scattering media are performed. The dependences of the measured signal on the concentrations of scatterers and fluorophore (protoporphyrin IX) under study are measured.     

Mixed polarization in determining the film thickness of a silicon sphere by spectroscopic ellipsometry

The effect of a spherical shape on the measurement result of spectroscopic ellipsometry (SE) is analyzed,and a method to eliminate this effect is proposed.Based on the simulation result of the SE measurement on a silicon sphere by ray tracking,we find that the sphere makes the parallel incident beam of the SE be divergent after reflection,and the measurement error of the SE caused by this phenomenon is explained by the mixed polarization theory.By settling an aperture in front of the detector of the SE,we can almost eliminate the error.For the silicon sphere with a diameter of 94 mm used in the Avogadro project,the thickness error of the oxide layer caused by the spherical shape can be reduced from 0.73 nm to 0.04 nm by using the proposed method.The principle of the method and the results of the experimental verification are presented.     

Mixed polarization in determining the film thickness of a silicon sphere by spectroscopic ellipsometry

The effect of a spherical shape on the measurement result of spectroscopic ellipsometry (SE) is analyzed, and a method to eliminate this effect is proposed. Based on the simulation result of the SE measurement on a silicon sphere by ray tracking, we find that the sphere makes the parallel incident beam of the SE be divergent after reflection, and the measurement error of the SE caused by this phenomenon is explained by the mixed polarization theory. By settling an aperture in front of the detector of the SE, we can almost eliminate the error. For the silicon sphere with a diameter of 94 mm used in the Avogadro project, the thickness error of the oxide layer caused by the spherical shape can be reduced from 0.73 nm to 0.04 nm by using the proposed method. The principle of the method and the results of the experimental verification are presented.     

X-ray fluorescence method for determining the thickness of an aluminum coating on steel

We have used an EDX-720 energy-dispersive x-ray fluorescence spectrometer to develop a technique for determining the thickness of an aluminum coating deposited on steel 47 NKhR. We have calculated the mass absorption coefficients for absorption of the fluorescent emission of nickel by the aluminum coating, where nickel is a major component of the substrate material. We have established and present the metrological characteristics.     

一种可溯源的光谱椭偏仪标定方法

提出了一种用X射线反射术标定光谱椭偏仪的方法.作为一种间接测量方法,光谱椭偏术测得的薄膜厚度依赖于其光学常数,不具有可溯源性.在掠入射条件下,X射线反射术能测得薄膜的物理厚度,测量结果具有亚纳米量级的精密度且与薄膜光学常数无关.在单晶硅基底上制备了厚度分别为2nm,18nm,34nm,61nm及170nm的SiO2薄膜标样,并用强制过零点的直线拟合了两种方法的标样测量结果,拟合直线的斜率为1.013±0.013,表明该方法可在薄膜厚度测量中标定光谱椭偏仪.     

A new method for determining birefringence dispersion

A method is proposed for the determination of birefringence in thin transparent anisotropic films. The modifications produced by the thin anisotropic films in the channeled spectra of an anisotropic crystal are used. The channeled spectra were recorded on a spectrophotometer provided with a device developed by us.     

激光透射成像法测量石英管的外径与壁厚

为了同时同位测量石英管的外径和壁厚,建立了激光透射成像系统,对系统测量原理进行研究。基于几何光学和菲涅尔公式,分别导出平行光垂直照射石英管后的透射光线偏向角、相对光强与入射光线离轴距离之间的关系;通过数值计算,分析了偏向角、相对透射光强随入射光线离轴距离的变化特点;针对物方远心光路,分析了光阑对偏向角和相对光强的限制;基于CCD成像原理,通过引入标定系数和补偿因子,导出石英管外径与壁厚的计算公式。实验结果表明:外径绝对误差和相对误差的平均值分别为0.119mm和0.91%,壁厚绝对误差和相对误差的平均值分别为0.153mm和6%。     

A method of determining the distribution of photoconductivity and its relaxation time over the semiconductor wafer thickness

A noncontact method is proposed to determine the depth profiles of photoconductivity and its relaxation time in a high-resistance plane-parallel semiconductor wafer placed at the center of an open confocal cavity normally to its axis and exposed to intensity-modulated light. The method is based on measuring the cavity transmission modulation depth at several frequencies for which the wafer optical thickness equals an integer number of half-waves and the wafer positions in which the phase difference between the interfering waves on the wafer surfaces is a multiple of π/2. The effect of experimental errors on the accuracy of the method is studied by computer simulation.     

Temperature properties of plate modes in quartz

The shear horizontal modes that occur in a quartz plate are studied both theoretically and experimentally. These modes are shown to possess a wide variety of temperature properties, including the characteristic behavior of the temperature coefficient of delay, which can take on negative, zero and record-breaking high positive values up to 350×10^?6/°C. The dependence of this coefficient on the mode number is explained by the varying partial contributions of three elastic moduli, c ₁₂, c ₁₄, and c ₄₄, to this coefficient.     

Effect of annealing temperature on determining trap depths of quartz by various heating rates method

The aim of this study is to determine the trap parameters (trap depth E, frequency factor s) of quartz using various heating rates method and also to investigate the effect of annealing temperature on determining trap depths. The method is based on the positions of the thermoluminescence peaks, obtained from the change in temperature of the peak at maximum caused by changing the heating rate at which the sample is measured. In the present work, powder quartz samples were annealed first at different temperatures before irradiation. Then samples irradiated to different doses were measured with a TL reader at different heating rates and the glow curves were recorded. In order to calculate the trap depth E and the frequency factor s, the glow parameter T_m was determined experimentally from the glow curve by measuring the shift of the maximum peak temperature depending on heating rate β. The calculation of trap parameters was repeated for each annealing temperature. Then the effect of annealing temperature on trap depths calculated by the various heating rates method was evaluated.     

Thermal wave method as a tool for determining the polarization profile in ferroelectric materials

The thermal square wave method based on irradiation of the crystal under investigation by a squarely modulated thermal wave at a particular frequency is described in detail. The choice of parameters for the quantitative determination of the pyroelectric characteristics of crystals is justified. The method is used to determined the conditions for the formation of a system of antiparallel domains in strontium barium niobate crystals.