Multiple-beam Interferometric Techniques Research Articles

Investigating the Mechanical Behavior of PGA/PCL Copolymer Surgical Suture Material Using Multiple-Beam Interference Microscopy

The article aims to investigate the mechanical behavior of polyglycolic acid PGA/polycaprolactone PCL copolymer surgical suture material. A suture fibre-drawing device was designed and calibrated to be attached with the multiple-beam interferometric technique. Multiple-beam interferometric technique of the Fizeau type, in transmission, was used to investigate the optical properties. The designed drawing device was used to stretch the suture fibre sample at different draw ratios to investigate the mechanical properties. Different values of stresses were applied by utilizing the suture fibre-drawing device. The influence of the applied stresses on the physical and structural properties was studied. The stress-strain curve, optical orientation factor, refractive indices, refractive index profiles, orientation angle, Young’s modulus, elastic shear modulus and compressibility were investigated for the PGA/PCL suture materials at different draw ratios. The behavior of the stress-strain curve of PGA/PCL suture materials takes the J-shape which agreed with the behavior of soft tissue. Illustrations using microinterferograms and graphs are given.

Structural and Optical Studies of Hot Wall Vacuum Evaporated CdTeSn Thin Films

Bulk compounds of CdTe, Cd0.25Sn0.75Te and Cd0.25Te0.75Sn have been prepared by direct reaction of their high purity (99.9999%) elemental constituents employing rotating furnace. The hot wall system is optimized for the deposition of prepared alloys by using molecular flow studies with Monte Carlo simulation technique. Thin films have been deposited on well cleaned glass substrates using the prepared alloys by the optimized hot wall vacuum evaporation system. The compositions of the prepared bulk and thin films have been identified using energy dispersive X-ray analysis. The compositions are found to be same for both the bulk and thin films as the prepared alloys. The structural properties of the deposited films have been studied using X-ray diffraction technique. The results show that all the films are crystalline in nature and the peaks in the XRD graph of CdTe correspond to cubic zinc blende structure and that of Cd0.25Sn0.75Te and Cd0.25Te0.75Sn compounds to rock salt structure. The lattice parameters and grain sizes of all the films have been evaluated. The surface morphology of the thin films is studied using Scanning Electron Microscope (SEM). The SEM analysis shows that surface of the films are smooth and crystalline in nature. The optical transmittance spectra of thin films were recorded using spectrophotometer in the range of wavelength from 190 nm to 2500 nm. All the films exhibit direct optical band gap and their values are 1.45eV (CdTe), 0.9eV (Cd0.25Sn0.75Te) and 1.1eV (Cd0.25Te0.75Sn). Thicknesses of the thin films have been determined by multiple beam interferometric technique.

Automatic determination of refractive index profile of fibers having regular and/or irregular transverse sections considering the refraction of light rays by the fiber

A new model, using non-destructive two- and/or multiple-beam interferometric techniques, is suggested for measuring the refractive index profile of fibers having regular and/or irregular cross-sectional shape taking into consideration the refraction of the light rays by the fiber. The proposed model is applied for three different fibers having different cross-sectional shapes and different refractive index profiles. These fibers are PPT, homogeneous fiber, with circular cross-section, graded index optical fiber of circular cross-sectional shape and Dralon fiber of irregular cross-section. To validate the proposed model it is used, firstly, to calculate the index profile for a standard PPT fiber. Secondly, the calculated results for the irregular Dralon fiber and GR-IN optical fiber are compared with that calculated using other conventional method. From this comparison, we recommend that the refraction must be taken into account to obtain accurate results especially for birefringent fibers and graded index optical fibers.

Effect of annealing on the structural properties of electron beam deposited CIGS thin films

CIGS bulk compound of three different compositions CuIn 0.85Ga 0.15Se 2, CuIn 0.80Ga 0.20Se 2 and CuIn 0.75Ga 0.25Se 2 have been prepared by direct reaction of elemental copper, indium, gallium and selenium. CIGS thin films of the three compositions have been deposited onto glass and silicon substrates using the prepared bulk by electron beam deposition method. The structural properties of the deposited films have been studied using X-ray diffraction technique. The as-deposited CIGS films have been found to be amorphous in nature. To study the effect of annealing on the structural properties, the films have been annealed in vacuum of the order of 10 − 5 Torr. The X-ray diffractograms of the annealed CIGS films exhibited peaks revealing that the annealed films are crystalline in nature with tetragonal chalcopyrite structure. The (112) peak corresponding to the chalcopyrite structure has been observed to be the dominating peak in all the annealed films. The position of the (112) peak and other peaks in the X-ray diffraction pattern has been observed to shift to higher values of 2 θ with the increase of gallium concentration. The lattice parameter values ‘a’ and ‘c’ have been calculated and they are found to be dependent on the concentration of gallium in the films. The FWHM in the X-ray diffraction pattern is found to decrease with an increase in annealing temperature indicating that the crystalline nature of the CIGS improves with increase in annealing temperature. The films grown on silicon substrates have been found to be of better crystalline quality than those deposited on glass substrates. The micro structural parameters like grain size, dislocation density and strain have been evaluated. The chemical constituents present in the deposited CIGS films have been identified using energy dispersive X-ray analysis. The surface topographical study on the films has been performed by AFM. The photoluminescence studies have been carried out and the results have been discussed. The thickness of the films has been determined by multiple beam interferometric technique.

Modified interferometric method for characterization of birefringent multi-media objects

In this work a new interference formula is derived and proposed for the simultaneous determination of layer width and directional refractive indices of multi-layer objects. This new formula can be applied for both oblique and normal incidence two- and multiple-beam interferometric techniques. Only the extraordinary fringe deflections in each layer of the multi-layer object image are measured. The measured data are substituted into this new formula, and the directional refractive indices and width of each layer can be calculated. In comparison with the well-known conventional interference formula, the measurement accuracy of this method is discussed. An example of applying the formula to data from irregular cellulose fibres (cotton and wood pulp fibres) is given.

Non-destructive multiple beam interferometric technique for measuring the refractive indices of lenses

An innovative approach for determining the refractive index of lenses has been reported. The lens as a specimen remains safe because neither it is touched nor any part of it is removed for experimentation. All the serious difficulties associated with refractive index measurements of glass material in the form of a lens have been set aside. For this purpose, the lens immersed in a liquid inside a glass cell has been used. Laser light is incident on Fabry–Perot (F–P) etalon, which forms the fringes in transmission side. This fringe pattern of circular rings is brought to the back focal plane of lens immersed in a liquid. A new mathematical formula, involving the diameter of interferometric fringes and refractive indices of liquids, is required for evaluating the refractive index of a glass sample in the form of a lens, have been deduced.

Non-destructive multiple beam interferometric technique for measuring the refractive indices of lenses

An innovative approach for determining the refractive index of lenses has been reported. The lens as a specimen remains safe because neither it is touched nor any part of it is removed for experimentation. All the serious difficulties associated with refractive index measurements of glass material in the form of a lens have been set aside. For this purpose, the lens immersed in a liquid inside a glass cell has been used. Laser light is incident on Fabry–Perot (F–P) etalon, which forms the fringes in transmission side. This fringe pattern of circular rings is brought to the back focal plane of lens immersed in a liquid. A new mathematical formula, involving the diameter of interferometric fringes and refractive indices of liquids, is required for evaluating the refractive index of a glass sample in the form of a lens, have been deduced.

Determination of the refractive index of fibres using the modified area method: I. Homogeneous fibres

The mathematical formulae for determining the mean refractive indices and birefringence of homogeneous fibres are modified. This modification depends on calculating the area under the fringe shift and cross-sectional area of homogeneous fibres having nearly circular cross-sectional area taking the refraction of the incident light beam by the fibre into consideration. The mathematical analysis for two-beam and multiple-beam interferometric techniques is dealt with. These formulae are applied to polypropylene fibres with draw ratios of 3.5 and 4 using the two techniques. A comparison between the results when using the new formulae and when neglecting the refraction has been studied. The diffraction of a He–Ne laser beam is used for determining the shape of the cross-sectional area of these fibres. Microinterferograms are given for illustration.

Interferometric studies on thin photoactive polymer films

Due to the importance of measuring the refractive index of optical waveguides, it is very important to find an accurate method to model the operating characteristics properly. The optical properties of thin photoactive polymer films are studied interferometrically using two different techniques, two and multiple beam. It is shown that the refractive index and birefringence of Disperse Red 1 doped with poly(methyl methacrylate) are independent of either the thickness of the film or the type of solvent used. A comparison between the two- and multiple-beam interferometric techniques for the determination of refractive index and birefringence is given. Both methods are evaluated and microinterferograms are given for illustration. Another comparison between the interferometric techniques and prism coupling technique is also given.

Opto-Mechanical properties of fibres. 7: Relation between cold Drawing behaviour of nylon 6 fibres from an Egyptian manufacturer and their optical properties

Optical properties change with strain produced by different stresses. Undrawn Nylon 6 fibres from an Egyptian manufacturer have been measured dynamically by interferometry. Both two- and multiple-beam interferometric techniques were used to determine refractive indices and birefringence of the investigated Nylon 6 samples with strain produced by different stresses. Using a micro-strain device attached to a microscope stage and through the application of the appropriate mathematical equations, the refractive indices and the birefringence values were determined as a function of the draw ratios. The resulting data were utilized to calculate the polarizability per unit volume, Poisson's ratio, the strain optical coefficient, and several other parameters and constants. Relationships between the various optical parameters and the draw ratios are plotted and the effect of draw ratio on the refractive index profile is studied. Microinterferograms are given for illustration.

A contribution to the study of optical properties of cylindrical step-index fibres

Both two-beam and multiple-beam interferometric techniques were used to determine refractive indices and birefringence of polypropylene fibres. The aim of this work is to suggest a method to calculate the value of refractive indices and birefringence of the fibre from the interferograms when it is difficult to detect the connection between the interference fringe in the liquid region and inside the fibre. Results are compared with those adopted from other interferometric methods and found to be in good agreement. Illustrations are given using microinterferograms.

A simple apparatus for film thickness measurements

An apparatus and method for thin-film thickness measurements using the multiple-beam interferometric technique of Fizeau fringes are described. The apparatus is simple in construction and to use, inexpensive and portable. It can be used in the range 30-350 nm with an accuracy of 2 nm for film thickness below 100 nm rising for 350 nm films.

Interferometric study of the microtopography arising from 35° domain walls in crystals of lithium niobate

The surface microtopography arising from the 35° domain walls in single crystals of lithium niobate has been studied in detail by optical and multiple-beam interferometric techniques. The a domain bands produce a change in level on the (10.0) surface. The surface angle between two adjacent a domains is found to be nearly 2° 18 minute, the calculated value being 2° 24 minute.

Interferometric study of domain structure in barium titanate

The surface microtopography arising out of the 90° domain walls in single crystals of Barium Titanate in the ferroelectric tetragonal state has been studied in detail employing optical and multiple beam interferometric techniques. The domain walls mark a change in level at the crystal surface and it is shown that the change in level is proportional to the distance between the domain walls. A step ladder structure is often found on the crystal surface which indicates, beyond doubt, the head to tail coupling of the dipoles. In a few cases, however, 90° wall configuration with head to head or tail to tail orientation has been observed. These laminae frequently advance in groups in the two perpendicular directions parallel to the edges of the crystal. As a result of the intersection of these groups the crystal surface becomes highly complicated with a step ladder structure in mutually perpendicular directions, terminating in a square base or at times in a point. In many cases, the multiple beam interferometric techniques have shown that the crystal surface is deformed with a cylindrical curvature: the axis of a cylinder being parallel to the edge of the crystal. Some times one observes the crystal having cylindrical curvatures in perpendicular directions.

Dislocations in silicon carbide crystals: Interferometric and X-ray study of polytypism

A number of silicon carbide crystals, some new polytypes, have been studied. Phasecontrast microscopic and multiple-beam interferometric techniques have been used to study the growth spiral structure on (0001) and for the measurement of spiral step heights. X-ray methods gave the lattice constants. The various silicon carbide crystals can be divided into the following categories by expressing the relationship between the step height of the growth spirals on (0001) and the measured height of the unit cell along thecaxis: (i) crystals in which there is direct correlation between the step height and the unit cell; (ii) those in which the step height is a multiple or submultiple of the unit cell; (iii) a very large unit cell size originating from a complicated growth pattern showing no direct correlation between the step height and the unit cell size; (iv) crystals consisting of a mixture of polytypes and exhibiting an interlaced type of growth spiral; (v) a gradual transition to crystals with unresolved structure and disordered types. Rhombohedral silicon carbide crystals growing from two dislocations, one positive and the other negative, are shown to lead to the creation of a positive and negative rhombohedron (i. e. obverse and reverse positions).

CXV. An interferometric investigation of the abrasion hardness properties of diamond

Summary The abrasion properties of several diamonds have been investigated using a multiple beam interferometric technique. The cube, dodecahedron and octahedron planes were abraded in various directions using a special micro abrasion tester. Abrasion only occurred in directions parallel to crystallographic axes; that is in four directions on cube planes and in two on dodecahedron planes, whereas no abrasion at all was produced on either natural or cleavage octahedron planes. Not all these directions were equally favourable; although it was found that an exact orientation reduced the vector effect. Taking the most favourable direction in each case the dodecahedron surfaces were easier to abrade than the cube surfaces. In addition the interferograms show that the abrading wheel moved in both lateral and longitudinal directions whilst abrading and at the same time probably suffered elastic deformation. It can be seen that the sides of an abrasion were highly polished and that there was no large scale deformation of the surrounding surface.