Interferometric measurement of refractive-index change in photosensitive glass

We report on a technique for determining the change in the refractive index of photosensitive glass. We have demonstrated our interferometer-based technique on fiber preform and bulk glass samples, achieving an optical-path-difference (OPD) repeatability of 0.2 nm. For the bulk glass sample we measured an OPD of 15.2 ? 3.0 nm, corresponding to an index change of 2.1 ? 0.7 x 10(-5). Our technique was found to be insensitive to the effects of photodarkening and material compaction.     

Effects of phase change on reflection in phase-measuring interference microscopy

We show by analytical and numerical calculations that the phase change on reflection that occurs in interference microscopy is almost independent of the numerical aperture of the objective. The shift of the microscope interferogram response due to the phase change on reflection, however, increases with the numerical aperture. Measurements of the interferogram shift are made with a Linnik interference microscope equipped with various numerical-aperture objectives and are reported and compared with theory.     

Offset of coherent envelope position due to phase change on reflection

Different materials with different phase changes on reflection affect the surface-height measurement when interferometric techniques are employed for testing objects constructed of different materials that are adjacent to one another. We test the influence of this phase change on reflection when vertical scanning interferometry with a broadband source is used. We show theoretically and experimentally that the strong linear dependence of the dispersion of the phase change on reflection preserves the shape of the coherence envelope of the fringes but shifts it along the optical axis by approximately 10-40 nm for metallic surfaces.     

Interferometric characterization of phase masks

We demonstrate a novel interferometric technique for highly accurate characterization of phase masks used in optical fiber grating fabrication. The principle of the measurement scheme is based on the analysis of the interference pattern formed between the first- and zero-order beams transmitted through or reflected from the grating under test. For spatial resolution of a few millimeters, our methods allow the determination of local variations of the order of 1-microm grating period with an accuracy of a few picometers. These methods are applicable to a broad class of diffractive grating structures.     

Interferometric measurement of fluorescence excitation spectra

A Michelson interferometer has been adapted as an excitation source for fluorescence spectroscopy. A moving fringe pattern was generated by linear displacement of the movable mirror of the Michelson interferometer coupled to a xenon-arc lamp. This spectrally modulated source was monitored by a reference photomultiplier and used for exciting a Rhodamine B solution. The fluorescence emission at >645 nm was detected by a second photomultiplier. The two interferograms were acquired by a dual-channel digital oscilloscope, and their discrete Fourier transforms and corresponding power spectra were generated in a computer. The power spectrum of the emission signal represented the excitation spectrum, as was confirmed by comparison with the absorption spectrum of Rhodamine B. Thisoptical arrangement is well suited for acquiring fluorescence excitation spectra in the optical microscopy of biological specimens.     

Interferometric measurement of the phase of diffracted waves near the plasmon resonances of metallic gratings

We propose a method for analyzing both theoretically and experimentally the behavior of the phase of the waves diffracted by gratings. The method is applied to the study of resonance phenomena. It is used for determining the optogeometrical parameters of a metallic grating. We show that the experimental setup, which is insensitive to mechanical drifts or thermal fluctuations, can be used for sensing purposes.     

Interferometric measurement of laser heating in praseodymium-doped YAG crystal

Temperature measurement is required for many applications but can be difficult in some cases. Laser heating or cooling studies demand accurate measurements of temperature changes. A Michelson interferometer configuration has been used to investigate laser heating in solids. An analytical formula was derived to estimate the temperature change from the fringe count by taking into account the temperature dependence of the sample length and refractive index. When 115?mW of a focused Ar+ laser beam (488?nm) passes through a Pr(3+)-doped YAG sample, its temperature increased by 11.7±1.0?K along the beam path due to nonradiative relaxation. The power dependence of the fringe count/movement was recorded. The temperature change was estimated by the interferometric method and is in agreement with that measured by a thermocouple.     

Interferometric measurement of J for arbitrary geometry and loading

International Journal of Fracture -     

Interferometric measurement of near-cylindrical surfaces with high amplitude resolution

Subaperture interferometric measurements of highly curved surfaces with a shape close to a cylinder have been performed in a normal-incident setup that consists of a Fizeau interferometer in combination with a plano-concave cylindrical lens. Since the field of view in the circumferential direction is limited by spherical aberration, the optical components were designed to minimize spherical aberration. For reference measurements a second plano-convex cylindrical lens was used. The subaperture setup leads to three-dimensional surface maps of the objects under test. To eliminate the influence of residual geometric aberrations, rectangular polynomials have been fitted and subtracted from the raw data. For deformations with spatial wavelengths below 30 mm, a rms amplitude resolution of 1 nm and a rms amplitude accuracy of 3 nm were achieved. Measurements on Wolter-type-I mirror shells are discussed in detail.     

Interferometric model for phase analysis in fiber couplers

An interferometric model is proposed to estimate the phase differences in lossless, strongly coupled biconical fiber couplers. This approximate method is simpler than the traditional s-parameter network theory-based analysis technique and minimizes the number of unknowns. The phase difference between the transmitted and coupled light fields is directly related to the field interaction and can be estimated by employing the energy conservation and mode orthogonality principles. The maximum coupling coefficient and dependence of phase difference on coupling conditions can be analyzed for multiport single-mode fiber couplers.     

相变储能材料研究进展

综述了固-固相变储能材料（s-S PCMs：sofid-solid phase change materials）、固-液相变储能材料（s-1 PCMs：solid—liquid phase change materials）的主要优缺点，并主要介绍了以下2种封装方式：（1）PCMs与基体材料复合制成定型PCMs，包括：与有机高分子材料机械共混、用无机多孔材料封装；（2）PCMs微囊化。此外，还分析了PCMs的主要应用领域及PCMs的主要研究方向。     

Interferometric phase reconstruction by nonuniform shifting of the reference beam

A method for phase measurement in common-path interferometers, believed to be novel, is presented. We use the property of phase reconstruction algorithms, such as the Carré and Hariharan algorithms, that do not require uniform phase across the reference beam. Only the ratio of the phase steps must be the same at each pixel. We show phase measurement and reconstruction in a common-path interferometer by shifting either the tilt or the focus of the reference wave front. We present a theoretical explanation of phase measurement using this property. We also present results from a proof-of-principle experiment using a scatterplate interferometer, in conjunction with the tilt phase-shifting technique, to measure the reflected phase of a test optical element. Furthermore, we present a computer simulation to demonstrate the mathematical validity of this measurement technique using defocus shifting, rather than tilt shifting, in the reference wave front.     

Interferometer for small-angle measurement based on total internal reflection

We describe a new method for angle measurement based on the internal-reflection effect and heterodyne interferometry. A novel prism assembly is designed that can always parallel retroreflect the incoming light beams so the optical configuration is compact. As a differential common-path optical configuration is integrated into the design, the linearity of the method is greatly improved. Details of theoretical analysis of the method and experimental verification of the principle are presented. The resolution can be better than 0.3 arc sec. The experimental results and further improvements of the proposed method are also addressed.     

Interferometric measurement of the profile of steeply sloped channels in metals

This article examines a problem related to the study of the surface of a metal form for printing official documents. A design of interferometric scanning profilometer is proposed and theoretically analyzed. The profilometer employs an unfocused laser beam that is wider than the channels. The reflected and scattered light wave is subjected to amplitude-phase and polarization analysis. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 14–16, May, 1998.     

Interferometric measurement of the refractive-index gradient distribution in gradient-index optical blanks

Anew interferometric method for measuring the refractive-index distribution in a plane-parallel section cut from a gradient-index lens blank is described. A standard double-pass interferometric scheme modified to provide a single pass of the beam through the investigated gradient-index sample is used. The two-dimensional variation of the refractive index in dimensions transverse to the sample surface is measured with an accuracy of better than 1 × 10(-4).     

Interferometric measurement of acoustic velocity in PbMoO4 and TeO2

We present a novel interferometric technique for the accurate measurement of acoustic velocity based on an optical phase shifter consisting of a pair of properly aligned acousto-optic modulators (AOMs). Results for the z-axis longitudinal mode velocities in lead molybdate (PbMoO(4)) and tellurium dioxide (TeO(2)) at 80 MHz are reported and compared with earlier results. A longstanding inconsistency in the PbMoO(4) velocity is resolved.