Circuit coupling method applied to bulk superconductors

This paper presents a new finite-element method for including a bulk superconductor in an electrical circuit. The method solves simultaneously the finite-element equations of A/spl psi/ formulation and the circuit equations. At the same time, a power law defines the superconducting properties. The method then compares the classical homogeneous model of a Bi-2223 tape to a multifilament model. The results of a simulation of conductors carrying alternative current while subjected to an external ac field are presented.     

Refractive-index profiling of embedded microstructures in optical materials

We describe use of a phase-sensitive low-coherence reflectometer to measure spatial variation of refractive index in optical materials. The described interferometric technique is demonstrated to be a valuable tool to profile the refractive index of optical elements such as integrated waveguides and photowritten optical microstructures. As an example, a refractive-index profile is mapped of a microstructure written in a microscope glass slide with an ultrashort-pulse laser.     

Refractive-index measurement of gradient-index microlenses by diffraction tomography

Diffraction tomography is applied to reconstruction of the gradient-index distribution of planar gradient-index microlenses, fabricated by thermal ion exchange. Measurements of the single-phase projections are performed by phase-shifting interferometry For reconstruction, the Rytov approximation for smooth inhomogeneities is applied. Results are compared with measurement results from other methods and simulation results.     

Refractive-index modifications of some polymeric materials by ion beams

Optical guides are realized by ion irradiation in three polymers: polycarbonate, HIRI, and CR39. Optical properties (index variation, loss) are compared. CR39 waveguides present the best performances (with losses as low as 1 dB/cm); the influence of a curing parameter (initiator concentration), which is directly related to CR39 density and refractive index, is studied.     

Refractive-index measurement of gases with a phase-shift keyed interferometer

The presented new type of interferometer combines the principle of two-beam interferometry and the technique of phase-shift keying of holographic gratings. On the basis of the phase-shift keying technique, the interferometer employs two different geometries for the recording and the readout process. Two holographic Bragg gratings are recorded in transmission geometry and simultaneously read out in reflection geometry using a tunable IR laser. Both gratings have the same grating period but a relative phase shift. The wavelength of the readout beam is fitted to the Bragg condition for the gratings. Using a tunable IR laser for the readout process, we can measure the spectral transfer function of both combined gratings. The shape of the measured transfer function is extremely sensitive to the phase shift between the two gratings. We demonstrate an application of this method by the measurement of refractive-index variations of gases due to pressure changes of the gases. The achieved resolution with respect to the measurement of phase shifts is approximately 1/40 pi. We present experimental investigations on two kinds of gas (an inert gas and a gas composition) as well as an efficient numerical approach to simulate the transfer function for Bragg gratings with a phase shift. Furthermore, we present a method to increase the resolution based on the controlled manipulation of the transfer function.     

Investigation and measurement of the particle shape factor for bulk materials

A new method of measuring the shape factor of the particles composing bulk materials and its theoretical basis are described.     

Electromechanical coupling constant extraction of thin-film piezoelectric materials using a bulk acoustic wave resonator

Thin-film piezoelectric materials such as ZnO and AlN have great potential for on-chip devices such as filters, actuators and sensors. The electromechanical coupling constant is an important material parameter which determines the piezoelectric response of these films. This paper presents a technique based on the Butterworth Van-Dyke (BVD) model which, together with a simple one-mask over-moded resonator, can be used to extract the bulk, one-dimensional electromechanical coupling constant K(2) of any piezoelectrically active thin-film. The BVD model is used to explicitly define the series resonance, parallel resonance, and quality factor Q of any given resonating mode. Common methods of defining the series resonance, parallel resonance, and Q are shown to be inaccurate for low coupling, lossy resonators such as the over-moded resonator. Specifically, an electromechanical coupling constant K(2) of (2.6+/-0.1)% was measured for an (002) c-axis textured AlN film with an X-ray diffraction rocking curve of 7.5 degrees using the BVD based extraction technique.     

Graphical representation of prism coupling into thin films

A natural framework for evaluating prism-coupler performance is provided by a recently developed geometrical construction in which refraction through a prism for an arbitrary angle of incidence is represented by an ellipse. The useful operating range of a prism coupler is represented by the portion of the representational ellipse that appears within a window determined by the mode propagation conditions of a thin-film-substrate system.     

High-accuracy measurement of the optical transmittance of optical bulk materials at deep-ultraviolet wavelengths

A measurement setup that is capable of measuring the internal transmittance of fused-silica prisms at 193 nm with a precision better than 0.01%/cm (3sigma) is presented. Its application to materials and wavelengths other than those that were chosen here for demonstration is straightforward. A lack of any standards makes it impossible to determine the absolute accuracy (also called measurement uncertainty) experimentally; however, calculations indicate that it is almost within the same margin as the precision.     

Determining thin film parameters by prism coupling technique

A new method for determining the absorption coefficients, refractive indices, and thicknesses of thin films is proposed. The method is based on the measurement of the angular dependence of the energy reflection coefficient of a light beam upon excitation of the waveguide or leaky modes by a prism coupler. The features of determination of the parameters of SiO_x films on silicon and glass substrates are considered.     

Integrated-optics semiconductor detector using a prism coupling device

A room-temperature integrated-optics semiconductor detector is proposed. The sensitive element of the detector is a thin film of antimony-activated tin dioxide deposited on a prism coupling element. The sensitivity of the structure to ammonia, alcohol vapor, and acetone impurities is investigated. The range of detectable ammonia concentrations is 10⁻⁴–10⁻⁶%. Pis’ma Zh. Tekh. Fiz. 25, 11–17 (December 26, 1999)     

Projection-aided videometric method for shape measurement of large-scale bulk material stockpile

Large-scale stockpiles are a common means for the storage of bulk material and their shape measurement is a prerequisite for effective transportation and logistics management. This paper proposes a projection-aided videometric method that is based on stereo vision and makes use of projections and epipolar geometry constraints to solve the correspondence problem. A prototype measuring system was developed that can work in real time and achieve measuring accuracy of 0.71?mm in terms of the flatness deviation and 0.54?mm in terms of the depth error, as proven by the experimental results.     

金属材料韧性损伤测量的电阻法

 研究了考虑塑性变形的基于电阻变化的金属材料韧性损伤测量公式,对A3低碳钢拉伸试样的韧性损伤进行TNI!．结果表明,电阻法的测量值与弹性模量下降法的结果相一致．指出用电阻法测量金属材料韧性损伤应考虑试样长度和横截面尺寸的影响;电阻法的可靠性在于试样低值电阻的精确测量．     

Small-angle measurement by use of a single prism

A new method of angle measurement based on the internal reflection effect is proposed that uses a single right-angle prism. We measure the angular displacement between a laser beam and the prism by detecting the changes in reflectance as a function of the angle of incidence. We achieve high linearity of measurement by taking the inverse of reflectance as the output. The inverse of reflectance is obtained from the intensities of the reflected and the transmitted beams measured by two photodiodes. Experiments with a prototype device have demonstrated that angle measurement with a range of ?500 arc sec, a nonlinearity error of ?0.1%, and a resolution of 0.1 arc sec can be readily achieved. The measurement range can be further increased with some sacrifice of linearity.     

Optical waveguide absorption sensor using a single coupling prism

We propose an optical waveguide sensor that uses a leaky guided mode for measuring absorption of liquid samples. The sensor is composed of a single coupling prism on which a cladding layer and a waveguide layer are deposited. The guided mode generates dips in the reflectance spectrum; the depths of the dips depend on the extinction coefficient of a sample facing the layer. The sensitivity of the sensor is controlled by the thickness of the cladding layer. A simple theoretical model has been developed to analyze the behaviors of the sensor. In experiments we obtained sensitivity 17 times higher than that obtained by the conventional attenuated total reflection method.     

声激励共振法测量微机械材料的杨氏模量

微机械材料的杨氏模量测量是随着微机械构件的产生而提出的一项新技术。文章综述了已有的测量微机械材料杨氏模量的方法。提出了用声激励共振法来测量微机械材料的杨氏模量。这种方法具有测试装置简单、测量容易、精度高等特点。