Interferometric Method For Measurement Research Articles

Agile linear interferometric method for carrier-envelope phase drift measurement

A bandwidth-independent and linear interferometric method for the measurement of the carrier-envelope phase drift of ultrashort pulse trains is demonstrated. The pulses are temporally overlapped in a resonant multiple-beam interferometer. From the position of the spectral interference pattern, the relative carrier-envelope phase between two subsequent oscillator pulses is obtained at data acquisition rates up to 200 Hz. Cross calibration has been performed by f-to-2f interferometry in two independent experiments. The optical length of the interferometer has been actively stabilized, leading to a phase jitter of 117 mrad (rms). These results indicate a reduced noise and quicker data acquisition in comparison with previous linear methods for measuring the carrier-envelope phase drift.

Characterization of convective heat transfer in channels of small cross section using digital interferometry

Forced convection in channels of small cross sectional dimensions has been recommended as an effective heat removal method for electronic components and packages. Many of the experimental results reported in the literature on the heat transfer performance of small-cross section channels are of contradicting nature, even though some generally agreeing results are also found. One of the probable reasons for the deviations, as suggested by investigators, is the intrusive nature of measurement techniques, which interferes with the flow field. Hence a non intrusive measurement technique is preferable for temperature measurement in small channels. The present work is aimed at developing an interferometric method for convective heat transfer measurement in a liquid medium flowing through channels of small cross sectional dimensions, with hydraulic diameters ranging from 12 to 3 mm and characterizing the nature of fluid flow and heat transfer in these channels. Mach–Zehnder interferometric arrangement is used to obtain the temperature distributions in water flowing through the channels, which are further analyzed digitally to obtain the local heat transfer coefficients and Nusselt numbers. The results are compared and contrasted with classical results for channel flow and heat transfer, and attempt has been made to interpret the variations and deviations observed. The experimental study has been performed under different fluid velocities in the laminar flow regime, and under various wall heat fluxes corresponding to the heat dissipation range expected in microelectronic devices. Parametric variations for the heat transfer performance have been obtained and correlated using the experimental results.

Tuning fork enhanced interferometric photoacoustic spectroscopy: a new method for trace gas analysis

A photoacoustic trace gas sensor based on an optical read-out method of a quartz tuning fork is shown. Instead of conventional piezoelectric signal read-out, as applied in well-known quartz-enhanced photoacoustic spectroscopy (QEPAS), an interferometric read-out method for measurement of the tuning fork’s oscillation is presented. To demonstrate the potential of the optical read-out of tuning forks in photoacoustics, a comparison between the performances of a sensor with interferometric read-out and conventional QEPAS with piezoelectric read-out is reported. The two sensors show similar characteristics. The detection limit (L) for the optical read-out is determined to be L opt=(2598±84) ppm (1σ) compared to L elec=(2579±78) ppm (1σ) for piezoelectric read-out. In both cases the detection limit is defined by the thermal noise of the tuning fork.

Modified Fabry-Perot interferometric method for waveguide loss measurement

An extension to the Fabry-Perot interferometric method is demonstrated to calculate the optical loss and the reflectivity for optical waveguides simultaneously. The method uses an excitation of the waveguide with a broadband amplified spontaneous emission source (a superluminescent diode in our case) and curve fitting to account for the change of input power, thereby simplifying the measurement procedure. The use of a broadband source as opposed to tunable lasers allows for simultaneous measurements over multiple wavelengths and decreased sensitivity to reflections in the cavity. Further, waveguides of different lengths are measured to calculate the optical loss and the reflectivity simultaneously. It is shown that, if the value for reflectivity is assumed, there could be a large error in the measurement of loss especially for short waveguides. Optical loss for ridge waveguides is measured and compared by using a tunable laser as the input source. The method can be used for a generic case where it is suspected that the input power changes during the measurement.

An Interferometric Method for High Extinction Ratio Measurements With 60-dB Dynamic Range

In this letter, we introduce a novel interferometric method for dynamic extinction ratio measurement of temporally demultiplexed pulses. A high extinction intensity modulator is used in order to temporally demultiplex the pulse train. The resulting extinction ratio is measured to be 44 dB. Our method has a dynamic range of ~60 dB. To our knowledge, this is the highest dynamic extinction ratio measurement method reported to date for high-speed optical modulators.

ATIR proximity sensing through an absorbing medium

In this paper we describe a new simple interferometric method for measurement of the thickness of a very thin quivette filled with absorbing liquid. The method is based on the interferometric restoration and analysis of both p- and s-components of the attenuated totally internal reflected (ATIR) field. Two different liquid samples were studied experimentally. The interferometric signal obtained by measurements is compared with the theoretical prediction.

Nanometer scale measurement of wear rate and vibrations by fiber-optic white light interferometry

A white light interferometric method for nanometer scale measurement of wear events by fiber-optic sensing configuration is presented. The proposed contactless technique is capable of measuring the wear rate and vibrations of the pin in a standard pin-on-disc tribometer remotely and simultaneously. All data are obtained by an interferometric reading of the sensing fibers displacement using a passive demodulation technique employing a 3 × 3 fiber-optic coupler and mechanical scanner. We obtained a pin position resolution better than 100 nm in the range of 400 μm as well as minimal detectable amplitude of the pin vibration of about 50 pm / Hz .

Voltage measurement based on the electrostrictive effect with simultaneous temperature measurement using a 3 × 3 fiber-optic coupler and low coherence interferometric interrogation

A fiber-optic interferometric method for remote voltage measurement with simultaneous temperature measurement is presented. A PMN electrostrictive transducer is employed as a voltage-to-displacement converter. The displacement is then interferometrically measured by the passive demodulation technique based on a 3 × 3 fiber-optic coupler. The third 3 × 3 coupler’s port and the same low coherence light source (LCS) are used for the interferometric temperature measurement, necessary for the correction of the electrostrictive coefficient values.

Absolute Refractive Index and Oscillator Model of Dispersion for Some Ferroelectrics with Pseudoilmenite Structure

The interferometric method for measurement of the absolute refractive index of the optical media with the accuracy of 0.00001 has been developed. The range of index and thickness measurements is not limited in principle. This method allows testing LiNbO3 and LiTaO3.

A new interferometric method for vibration measurement by electronic holography

Electronic holography is a well-established technique used in real-time, non-contact, whole-field displacement measurements. When using the real-time, time-averaged method for vibration measurments, the quantitative interpretation of dense fringe patterns is difficult because of speckle noise. Even when speckle-reducing procedures are used, such as multiple-frame averaging or rotation of the illumination beam, the remaining speckles and decreasing visibility of higher-order Bessel fringes are serious limitations. The primary objective of this paper is to present a new realtime, interferometric method for mechanical vibration measurements and the associated quantitative interpretation. The fringe pattern obtained by this method is quasi-binary and half as dense as in the time-averaged method. The method greatly improves the overall visibility (contrast, resolution) of vibration fringe patterns without any sacrifice in the real-time capabilities. Quantitative fringe interpretation is straightforward and based on binary fringe tracking. It allows quantitative measurements in situations where the time-averaged fringe processing fails.

Modern optoelectronic methods for non-contact deformation measurement in industry

Two different types of optoelectronic method for non-contact deformation measurement are described: the ray method and the interferometric method. The ray method is based on the law of reflection and can be used for large continuous reflective surfaces, which behave approximately as deformable mirrors of a general type. The work is focused on several theoretical and experimental aspects of evaluation of the deformations with the ray method, especially on problems of measuring extended objects in engineering practice and automatic processes for evaluation of deformations. We also propose a technique for the smoothing of continuous optically rough surfaces to allow successful application of the ray method for deformation measurement. The interferometric measurement methods are based on the principle of interference of two coherent wave fields and subsequent evaluation of the interference pattern. In this work we describe a proposed optical method for measuring static deformations based on the interference of coherent wave fields and a phase shifting procedure. Detailed analysis of the measurement and evaluation process with respect to the most important measurement factors is performed.

Low-coherence interferometric method for measurement of displacement based on a 3 3 fibre-optic directional coupler

An interferometric method for measurement of displacement based on a 3 × 3 fused fibre-optic directional coupler is described. The target position within one interference fringe is obtained with high resolution from phase-shifted signals generated in photodiodes attached to the input ports of two couplers. With the help of the spiral Lissajous representation of the same signals the degree of coherence and then the order of the interference fringe are determined. A resolution of around 50 pm over the range of 15 µm has been achieved with a superluminescent diode as a source.

Phase profiles of transmitted light through glass-particle-dispersed epoxy-matrix composites

Abstract The phase profile of a transmitted laser beam through glass-particle-dispersed epoxy-matrix composites was measured using the interferometric measurement method. The effect of dispersed particles on the light scattering behaviour of the composite was determined from the difference between the in-line and total light transmittance. The difference between the light transmittances increases with increase in the particle volume fraction and this result indicates that the glass particles are a major source of light scattering in the composite. The phase profile changes with the addition of glass particles; a higher particle volume fraction yields a larger phase profile distribution. This result demonstrates that the phase profile of the transmitted light is strongly correlated with the total amount of light scattering source in the composite. The measured phase delay becomes pronounced on increasing separation from the laser beam axis and this behaviour is explained by increase in the laser beam path ...

Phase profiles of transmitted light through glass-particle-dispersed epoxy-matrix composites

Abstract The phase profile of a transmitted laser beam through glass-particle-dispersed epoxy-matrix composites was measured using the interferometric measurement method. The effect of dispersed particles on the light scattering behaviour of the composite was determined from the difference between the in-line and total light transmittance. The difference between the light transmittances increases with increase in the particle volume fraction and this result indicates that the glass particles are a major source of light scattering in the composite. The phase profile changes with the addition of glass particles; a higher particle volume fraction yields a larger phase profile distribution. This result demonstrates that the phase profile of the transmitted light is strongly correlated with the total amount of light scattering source in the composite. The measured phase delay becomes pronounced on increasing separation from the laser beam axis and this behaviour is explained by increase in the laser beam path in the composite caused by the light scattering.

Analysis of Phase Evaluation Algorithms in an Interferometric Method for Static Deformation Measurement

This article describes and analyses an interferometric method for measuring displacements and deformation. The method can be used for a very accurate evaluation of the change in the surface shape of structures used in industry. The paper proposes several multistep phase calculation algorithms and describes an automatic evaluation process using the measurement technique. A complex analysis is also performed of various factors that can have a negative effect on the practical measurement and evaluation process. An analysis is made of the proposed multistep phase calculation algorithms using the proposed error model. It is shown that the resulting phase measurement errors can be effectively reduced by using suitable phase calculation algorithms. The analysis can be applied for a complex comparison of the accuracy and stability of such algorithms.

A study of factors affecting solder joint fatigue life of thermally enhanced ball grid array assemblies

In this study, a finite element study of design factors, including material constants and geometry parameters, affecting fatigue life of solder joints of a typical cavity‐down Thermally Enhanced Ball Grid Array (TEBGA) assembly subjected to an accelerated temperature cycling load is performed. In order to precisely characterize the fatigue life of solder joints, the geometry profile of solder joints within the package is substantially predicted using an energy‐based method‐the Surface Evolver (see, e.g., Brakke, 1994; Chiang et al., 2000). In addition, a finite‐volume‐weighted averaging technique is proposed to describe the strain/stress response of solder joints at material/geometry discontinuities. The analysis employs a plane strain FE model with the purpose of reducing the computational cost. To validate the FE modeling so as to corroborate the nonlinear and complex mechanical behaviors of materials in the assembly, a typical interferometric displacement measurement method— Moire interferometry (see, Han and Guo, 1995) and 3‐D solid modeling are used. Through the parametric design of the fatigue life of solder joints, the reliability characteristics of the TEBGA assembly are then effectively identified.

Interferometry-based measurements of oil-film thickness

Measurement of the thickness of thin lubricant films separating rotating surfaces in elastohydrodynamic experiments presents some challenging problems. The nature of the experimental apparatus inhibits the use of most commonly applied interferometric phase measurement methods. Also the absolute thickness of the separating film must be determined, as opposed to relative distances that would be sufficient in most other measurement scenarios where interferometry methods are used. In this paper, computer-based analysis of interferograms recorded using an elastohydrodynamic lubrication Fitzeu interferometer (a so-called ball-and-disc apparatus) is discussed, the main objective being to extract the absolute oil-film thickness. Intensity based methods (most importantly, calibration look-up procedures where colour parameters from recorded dynamic interferograms are compared with table values corresponding to known film thicknesses, but also a phase measurement approach based on multi-channel interferometry using trichromatic light) are described. A discussion regarding compensation for measurement errors due to the pressure dependence of the refractive index of the lubricant is also included.

Effect of Polarization Mode Coupling on Extrema Counting Fixed Analyzer PMD Measurement Method

We describe the effect of polarization mode coupling in the single-mode optical fibers on the extrema counting fixed analyzer (FA) polarization mode dispersion (PMD) measurement method. We define the polarization mode coupling coefficient for the over (or under) estimation which occurs with the FA method. We investigate the polarization mode coupling coefficient experimentally by comparison with the air-path (cross-correlation) type interferometric PMD measurement method. Moreover, we discuss the polarization mode coupling experimentally as well as analytically by using pseudo-polarization mode coupling which we obtained by splicing highly birefringent (B≅4.5×10−4) polarization maintaining fibers (PMFs) with the random splice angles. The results show that the PMD τ of the single-mode optical fibers which has random polarization mode coupling can be approximated by multiplying the PMD τ obtained using the FA method with the random polarization mode coupling coefficient k≅0.82.

An integrated optical set-up for fluid-physics experiments under microgravity conditions

An integrated optical set-up for fluid-physics diagnostics is proposed. The combined diagnostic tools are direct visualization, the schlieren technique, electronic speckle-pattern interferometry, differential interferometry, digital holography and holographic interferometry with a photorefractive crystal. The sharing of most of the optical lenses allows a compactness of hardware compatible with space-application requirements (the Fluid Science Laboratory for the International Space Station). Performances and complementarity of techniques are discussed. Interferometric methods for refractive-index measurement are compared and preliminary experimental results are given.

An experimental/analytical comparison of three-dimensional deformations at the tip of a crack in a plastically deforming plate. I : Optical interferometry and experimental preliminaries

A critical examination of measured and computed three-dimensional deformations in the vicinity of a crack in an elastic/plastic plate subjected to three-point-bending are presented in a series of three papers. The aim is to apply interferometric measurement methods to the large plastic deformation at the tip of a crack in a ductile steel, and to assess the current ability to model that deformation numerically. Comparison between the precise interferometric measurements and the finite element model, which has been closely matched to the physical specimen, including internal tunneling of the crack, indicates good agreement up to 75 percent of the ultimate failure load; above that level, discrepancies increase to levels on the order of 25 percent. It also develops that out-of-plane measurements are less than optimal for deducing in-plane stress and deformation states. This finding implies consequences for working with caustics and similar methods when applied to cracks in plastically deforming solids. This first paper presents a description and assessment of the experimental methods and outlines the fracture experiment itself. The second paper describes the material characterization to closely match the finite element model to the physical fracture specimen, as well as a description of the finite element model itself. The third paper presents the results of the comparison between experiment and model, as well as some additional results from the numerical model alone.