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Abstract. The structure of vacuum-deposited cuprous telluride CuiTe films deposited on carbon substrates was observed by means of an electron microscope. Films on glass substrates were also investigated by X-ray diffrac-• tion. The optical constants (the refractive index n and the extinction coefficient k) of Cu2Tc thin films were determined from the measured transmittance and reflectance at normal incidence of light in the wavelength range 0.4 gm to 2.5 gin. The variation of the optical constants with thickness for different evaporated films have been determined. 78.65 Cuprous chalcogenides are of considerable scientific and technical interest in view of their potential applications as thermoelectric materials and in various electronic devices where they are primarily used as P -components in certain types of heterojunctions [1]. PACS:The structure of copper telluride has been studied by electron and X-ray diffraction [2][3][4], where it was found that thin films of CugTe systems may be formed in amorphous or different crystalline states depending upon the conditions of preparation such as the type and temperature of the substrate. Sokol et al. [5] prepared Cu2Te films by a laser technique and studied the effect of annealing temperature on the film structure. They showed that annealing induced a hexagonal-cubic transition at T> 200 ° C. Nikam [6] showed that the vapour-phase deposited films of copper telluride on glass and rocksalt substrates at higher temperature exhibit five phases, which are tetragonal, normal hexagonal, hexagonal super structure, normal cubic (ao = 0.635 nm) and cubic super structure (ao = 1.27 nm). The most frequently appearing phases are the hexagonal and cubic. He also obtained patterns corresponding to the phase Cu2_xTe * Address for correspondence: M. S. E1-Bahrawi, 90A, Ahmed Oraby Str., Apt. 502, E1-Mohandessein, Giza, Egypt having tetragonal structure (ao = 0.398, co = 0.612 nm) at temperatures up to 200 ° C. Baranova [7] studied the crystal structure of thin films of the hexagonal fin-phase of the Cu-Te system by electron diffraction and found the lattice parameters ao = 0.417 nm and Co = 2.165 nm.On the other hand, no detailed studies of the optical properties of Cu2Te thin films were carried out except those of Goswami and Rao [8]. They studied the optical properties of evaporated films of cuprous telluride and cuprous selenide in the visible region and reported that vacuum-deposited films of Cu2Te showed a semi-metallic behaviour as absorption was due to free charge carriers only.The aim of the present work is to study the dependence of the structure of thin evaporated films of Cu2Te, deposited on glass and carbon substrates, on the film thickness. The optical constants n and k have been obtained in the wavelength range 400-2500 nm.

Digital holography (DH) which is the technology of acquiring and processing measurement data via a CCD camera is spreading to industrial applications, finds wide employment in engineering problems of testing and investigation. In this paper, a simple digital holographic system, comprising a He-Ne laser source, CCD camera and analyzing software, is used for testing surface flatness and detecting the presence of a propagating crack on the surface plane and the effect of the crack on the neighborhood. Phase variations across the surfaces planes are extracted to represent the surface deviation from a reference plane. The analysis methods differ according to the interference fringes in the recorded holograms. Both fringe tracking and Fourier transform with phase unwrapping methods are used in the interpretation of interferometric fringe patterns.

The paper exploits absolute distance measurement with traceability to the international system (SI) of units of length. In the present work, the diode pumped Nd:YVO 4 /KTP polarised green laser is used to measure a distance Δl between two positions without the need for a reference standard. To comprise a synthetic wavelength λ s suitable to the range of the distance, the output wavelength generated by the frequency doubling is shifted by Δλ by controlling the injection current, and a set of shifted wavelengths are produced to form λ s. The output signal is sent to the interferometer by an optical fibre after being enhanced with a speckle removal unit. The measurement starts by identifying the zero position where no shift in the interference fringes is observed during sweeping the wavelengths, while at the distance Δl a deviation in the interference pattern is observed. This deviation is analysed by Fourier transformation to extract the phase change Δϕ and determine the distance value. To prove the reliability of absolute distance measuring interferometer, some measurements are made for various ranges with evaluation of both repeatability and uncertainty. The discussed technique can measure 100 mm with uncertainty ±16 µm.

The present work discusses the optical fiber strain induced by the thermal and the mechanical effects. Two different optical fibers of different core diameters were used in the study. The thermal effect was induced by temperature control system in order to raise optical fibers temperatures to controlled values. The mechanical stress was induced on the optical fibers by a micro mechanical stage. The sensitivity of the optical fibers to both effects was studied by speckle pattern correlation in which the speckles are recorded at each disturbance and analyzed. By tracing the recorded speckles , x and y displacements could be measured and the strain could be determined in two dimensions. Power attenuation in each fiber was studied in each case as well. Both speckle correlation and power attenuation techniques used in the study showed similar indication on the sensitivity of the optical fibers to the external disturbers.