Interferometric determination of refraction and dispersion of a birefringent material: numerical procedure

Air, liquid and solid sample interferometric gaps of the same thickness and simultaneously enclosed in a wedge interferometer are used to produce fringes of equal chromatic order. A mica sample of dimensions 2×5 mm² and an immersion liquid of the same refractive index are used. A single shot interferogram containing fringes in the three gaps is sufficient to deduce the needed experimental data. Locations of fringe maxima are introduced in a numerical procedure to retrieve the sample and liquid refractive indices across the visible spectrum. The numerical procedure is based on a simple dispersion function of wavelength and wavenumber. A modified two-term Sellmeier dispersion formula has been used for fitting the experimental data and deducing the needed dispersion parameters.     

Application of multiple-beam white-light fringes for measuring the refraction and dispersion of mica

Multiple-beam white-light interference fringes are applied to measure the two refractive indices of a mica sample and their dispersion across the visible spectrum. In addition, the mica birefringence and its dispersion are measured. A mica sample of dimensions 2 × 5 mm² and an immersion liquid of nearly the same refractive index are used. Only a single shot interferogram is needed to measure all the aforementioned parameters. Cauchy's and a modified single-term Sellmeier dispersion formula are used for fitting the experimental data and extracting the parameters required.     

Interferometric determination of refraction and dispersion of human blood-serum, saliva, sweat and urine

Multiple-beam interference fringes of equal chromatic order are produced in air and liquid sample interferometric gaps. The two gaps are of the same thickness and simultaneously enclosed in a wedge interferometer. A single shot interferogram containing fringes in the two gaps is sufficient to deduce the needed experimental data. Locations of the fringe maxima, in the two gaps, are introduced in a non-numerical procedure for determining the gap thickness and the liquid-phase refractive indices across the visible spectrum. The method has been used for measuring the phase refractive indices of human blood-serum, saliva, sweat, urine and water liquids. A third-order polynomial dispersion relation is applied for fitting the measured phase indices. Group refractive indices have been derived and fitted to the same dispersion formula.     

云母晶体双折射率色散特性的研究

针对云母晶体材料本身性质所决定的双折射率色散关系不一致性,给波片设计带来非常不利的影响,提出偏光干涉法研究云母的色散特性.即由分光光度计测量出云母晶体的偏光干涉谱,通过对干涉谱极值点所对应波长的精确判断,准确计算出极值点的最大双折射率,获得从紫外至近红外光波段云母晶体的双折射率色散曲线,经多项式拟合数据处理,得到任意波长的双折射率色散公式.为求解不同温度任意波长的云母晶体双折射率提供了一种精确简单的方法,对云母晶体器件的设计与使用有重要的理论依据和参考价值.     

Group refractive index measurement by fringes of equal chromatic order

Fringes of equal chromatic order in transmission across a thin liquid or a thin solid sample inside a wedge interferometer, followed with a grating spectrograph, are produced. A single-shot interferogram of the air and sample regions is recorded. Locations of fringes maxima in the air region are fitted in a numerical procedure based on Cauchy's dispersion function. Then it is used for measuring the interferometric gap thickness. The order of interference in the sample region is represented by a third-order polynomial in the wavenumber for deducing the sample group refractive index. An error analysis of the measured group refractive index is given. The method is applied for measuring the group refractive index of water and mica samples across the visible spectrum. The method measures both the sample thickness and its group refractive index. It is static with no moving parts and suitable for thin liquid or solid samples without immersion liquids.     

Extracting energy and structure properties of glass-forming liquids from structural relaxation time

A comprehensive examination of the kinetic liquid model (Wang et al 2010 J. Phys.: Condens. Matter 22 455104) is carried out by fitting the structural relaxation time of 26 different glass-forming liquids in a wide temperature range, including most of the well-studied materials. Careful analysis of the compiled reported data reveals that experimental inaccuracies should not be overlooked in any 'benchmark test' of relating theories or models (e.g. in Lunkenheimer et al 2010 Phys. Rev. E 81 051504). The procedure, accuracy, ability, and efficiency of the kinetic liquid model are discussed in detail and in comparison with other available fitting methods. In general, the kinetic liquid model could be verified by 17 of the 26 compiled data sets and can serve as a meaningful approximative method for analyzing these liquids. Nonetheless, further experimental examinations in a wide temperature range are needed and are called for. Through fitting, the microscopic details of these liquids are extracted, namely, the enthalpy, entropy, and cooperativity in structural relaxation, which may facilitate further quantitative analysis to both the liquidus and glassy states of these materials.     

椭偏法测量云母波片相位延迟量及双折射率(英文)

为了得到云母波片的相位延迟量和双折射率随波长的变化关系,利用椭偏光谱仪连续测量了云母波片在400～770nm光谱范围内的延迟量.在对云母波片进行校准后,测量的数据被光电探测器收集并输送到计算机,根据输出的数据可以得到云母波片的相位延迟量随波长的变化.利用测得的延迟量计算出了云母波片在一定光谱范围内的双折射率,得到了云母波片的双折射率色散曲线,并通过拟合得到了双折射率色散公式.该方法能测量任意波片的相位延迟量,并且具有测量方便、周期短、精度高等特点.     

反演与拟合相结合处理核磁共振弛豫数据的方法

讨论非负最小二乘（NNLS）法和非线性拟合在分析处理核磁共振（NMR）弛豫数据中的应用.同时将二者结合，提出用NNLS的反演结果来设定非线性拟合初值的方法，并用计算机模拟和实验证明了该方法在分析处理NMR弛豫数据中的有效性. 关键词： 非负最小二乘法 非线性拟合 核磁共振 弛豫时间     

Birefringence of muscovite mica

Birefringence of muscovite mica (n_e−n_o) is usually calculated from the dispersion relations of the indices n_e and n_o. As small differences between relatively large experimentally-measured values, the few available data for birefringence of mica are widely distinct and sometimes contradict basic experimental facts. A different procedure is adopted in this work to measure birefringence directly as a single quantity in terms of the thicknesses of mica plates and the wavelengths at which they act as quarterwave or halfwave phase retarders. Birefringence is found to decrease gradually from −0.0040 at 420 nm to −0.0046 at 700 nm in conformity with pertinent independent experimental results.     

Estimation of Lagrangian parameters from a diffusion experiment

Summary Taylor's statistical theory in the limits of small and large diffusion times is used to assess the Lagrangian parameters of a local atmospheric turbulence. Experimental data, representing the disperison of tracers in the atmosphere, are examined in order to derive the values of the local turbulence parameters pertaining to the Hanford-67 (Nickola P. W., 1977) experiment. Once determined, these Lagrangian parameters allow for a renormalization of the lateral dispersion as a function of time, that exhibits data dispersion smaller by two to three orders of magnitude, as compared to that obtained by normalization through the use of corresponding Eulerian parameters. This closer packing of the experimental data allows for a more precise fitting of a theoretical curve that is basic to the determination of local Lagrangian velocity autocorrelation coefficients. The authors of this paper have agreed to not receive the proofs for correction.     

Non-destructive collimation technique for measuring glass constants using a Ronchi grating shearing interferometer

A non-destructive liquid immersion collimation technique in combination with a Ronchi grating shearing interferometer has been used for determining the constants of a transparent glass material, especially when it is in the form of a lens. Due to its simplicity and the fact that it will work equally well at any wavelength, the technique is superior to existing methods for determining the various glass constants (refractive index, Abbe number or v-value, partial dispersion factor etc).The shearing fringes appearing inside a Ronchi-gram are adequate to locate the exact position of the point source which has been treated as the target in the present communication. The fringe-free space in the overlapping region between the two laterally displaced spherical wavefronts indicates the sharply focused position of the target which corresponds to zero defocusing. In this way the target displacements with different liquids are determined.     

Optical anisotropy of a biological tissue under conditions of immersion clearing and without them

The optical anisotropy of a biological tissue is studied under conditions of immersion clearing of the tissue and without them. It is shown that the rate of immersion clearing of a biological tissue depends on its type and is determined by the rate of diffusion of immersion liquids into the sample. The parameters that characterize the rate of diffusion of an immersion liquid into a biological tissue are determined. The types of anisotropy of different samples of biological tissues are found. Based on the Müller matrix formalism, a model for calculating the spectrum of collimated polarized transmission of a biological tissue is constructed. Comparison of calculated and experimental transmission spectra of biological tissues showed their good quantitative coincidence.     

Production of polydisperse bimodal liquid-droplet aerosol in a vibrating-rod generator

Experimental data for the dispersion of a liquid using a curved-end thin rod partially immersed in it and oscillating with a high frequency are reported. Depending on immersion conditions, the finely dispersed phase of a liquid-droplet aerosol can be obtained by exciting capillary standing waves and generating large drops emitted from the end face of the rod in the form of a directed jet.     

Visualization of Isofrequency Contours of Strongly Localized Waveguide Modes in Planar Dielectric Structures

An experimental method has been proposed to study the dispersion properties of optical surface and waveguide modes in planar structures. An experimental setup involves a microscope with a high numerical aperture objective and a hemispherical solid immersion lens made of zinc selenide in contact with the sample surface. The reflection from the sample is detected in the back focal plane of the system. Such a configuration makes it possible to study strongly localized states with an effective refractive index up to 2.25 in the visible and near infrared spectral ranges. For a thin silicon layer deposited on a glass substrate, the possibility of visualization of isofrequency contrours with polarization resolution and the reconstruction of dispersion of waveguide modes depending on the direction of their propagation has been demonstrated.     

Physical interpretation of a modified Lorentz dielectric function for metals based on the Lorentz–Dirac force

It is proposed that a recently used ad hoc modified Lorentz dielectric function for metals can be physically interpreted via the Lorentz–Dirac force. The Lorentz–Dirac force considers the radiation reaction of electrons, an effect that is ignored in classical dispersion relationships. A suitable reduced order form of the Lorentz–Dirac force that does not suffer from pre-acceleration and runaway artifacts is employed in the derivation of the modified dispersion model. The frequency characteristics and the causality of the Lorentz–Dirac dielectric model are studied in detail. Furthermore, the superiority of the Lorentz–Dirac dielectric function as a means of improved fitting of experimental data is demonstrated for gold, silver, and silicon in the infrared and optical region.     

The Paul wavelet algorithm: an alternative approach to calculate the refractive index dispersion of a dielectric film from transmittance spectrum

A new application of the Paul wavelet algorithm was presented to determine the refractive index dispersion of a dielectric film from transmittance spectrum in the visible and near infrared region. The developed algorithm was tested by simulated data and experimentally applied to a sample of mica. The obtained refractive index dispersion determined by the Paul wavelet algorithm was compared with the refractive index values determined by the envelope and fringe counting methods, and also with the established result. It was shown that the degree of the Paul wavelet has a major effect on the outcome of a refractive index determination. The noise immunity of the presented method was shown by the simulation study.     

Self-assembled monolayers of decanethiol on Au(111)/mica

We report here a preparation for thin gold films on mica substrates. We have investigated the influence of the substrate temperature and the evaporation rate on the morphology of the films. After careful outgasing of the substrate, 100 nm of Au is evaporated onto the mica surface maintained at high temperature. After slow cooling, ex situ characterizations are performed using AFM and STM. For our purposes, the best compromise between roughness and grain size is found to occur for an evaporation rate of 2 ?s^-1 onto a mica substrate maintained at 460 C. We have used these substrates for STM and AFM study of decanethiol self-assembled monolayers (SAMs). We present results for gold samples immersed for a few seconds in decanethiol solutions, revealing an incomplete organization of the films. The organization process is discussed through comparison between AFM and STM data recorded on the SAMs. Then we present molecular resolution STM pictures of ordered SAMs for longer immersion times. Received 25 May 1999     

Sound waves in a liquid with polydisperse vapor–gas bubbles

A mathematical model is presented for the propagation of plane, spherical, and cylindrical sound waves in a liquid containing polydisperse vapor–gas bubbles with allowance for phase transitions. A system of integro-differential equations is constructed to describe perturbed motion of a two-phase mixture, and a dispersion relation is derived. An expression for equilibrium sound velocity is obtained for a gas–liquid or vapor–liquid mixture. The theoretical results agree well with the known experimental data. The dispersion curves obtained for the phase velocity and the attenuation coefficient in a mixture of water with vapor–gas bubbles are compared for various values of vapor concentration in the bubbles and various bubble distributions in size. The evolution of pressure pulses of plane and cylindrical waves is demonstrated for different values of the initial vapor concentration in bubbles. The calculated frequency dependence of the phase sound velocity in a mixture of water with vapor bubbles is compared with experimental data.     

Structure and correlation in liquid alloys by X-ray and neutron diffraction

A method for obtaining information about correlation in a liquid or amorphous alloy is presented. The explicit structure in a binary could in principle be determined from three independent diffraction patterns. It is relatively much simpler to measure and analyse the x-ray and neutron intensity patterns and with these alone obtain considerable correlation information, even if more than two atom types are present, by calculating the ratio of the two experimental radial distributions. For the binary the relevance of the ratio derives from the fact that each distribution is a sum of the radial distributions of the three types of atom-pairs, each term being weighted by the appropriate product of scattering amplitudes. The structure of the sample can be analysed by comparing the ratio for any interatomic distance to the values it would have for pure A-A, pure B-B, pure A-B, and random pairing. In a true liquid the results are semiquantitative. In an alloy with well-defined short-range order, the correlation of these close pairings can be clearly determined. Results are shown for liquid NaK and vitreous silica. For any alloy the experimental results would serve to test structural models.     

Frequency power law of material damping

The experimental studies often show that the damping in various solid materials increases with frequency over a finite bandwidth, and the increase is weak if the damping is low. A frequency power law is suggested and discussed in this paper to describe this damping behaviour with special respect to the low loss resilient materials used for sound and vibration control. The dynamic modulus as a function of frequency is determined from the loss modulus through the Kramers-Kronig dispersion relations to satisfy the causality requirement. It is proved that the dynamic modulus obeys the frequency power law of the same type as the loss modulus. In addition, it is proved that the weak frequency dependences of damping properties are inevitably associated with the low loss factor. Examples of fitting the frequency power law to experimental data on some materials of acoustical purposes are presented.