<p>A ray-theoretic analysis of the problem of discontinuity in a linear guide is presented. The fields in the guides are expressed as superposition of plane wave components determined by subjecting the fields to the process of Fourier transformation. The reflected fields are finally synthesized by modifying these plane wave components by the corresponding Fresnel coefficients at the plane of discontinuity. The results obtained are compared with those obtained by other methods.</p>
In the present work a polarisation sensitive trangular path interferometer is developed to analyse the photoelastic stress
pattern. To increase the sensitivity of the proposed interferometer a birefringent lens is used as a longitudinal interferometer to generate background fringes. The stress-induced birefringence of the sample will modify the fringe pattern, which gives a method for measurement of stress distribution of the sample. The method has all the advantages of a common path interferometer.
A confocal microscopic setup with a pair of birefringent lenses having their crystal axes crossed is used to measure birefringence of thin samples. The method can be used to measure phase down to the order of /10. The fast and slow axes of the object also can be identified. The principle of the method along with the experimental setup is described. Some first-order experimental results are also presented.
A method for measurement of refractive index profile of a GRIN system is developed based on a longitudinal interferometer using a birefringent lens. The fringe pattern so generated is made to traverse through the sample under test. The modification of the fringes gives a measure of the refractive index profile. The fringe patterns both in presence and absence of the test samples are grabbed by a CCD camera and further processed by a computer. The basic software required for the same is being developed. Some experimental results are presented.
The design and fabrication of a fiber optic pH sensor working on the basis of evanescent wave absorption is presented. A pH sensitive dye is immobilized on the uncladded portion of the optic fiber by sol-gel route. The sensitivity of the device is found to increase when multiple sol-gel coatings are used as the cladding in the sensing region. The sensor response and its dynamic range are reported for two pH indicator dyes, vis. bromocresol purple and bromocresol green.
A scheme for combining a common path triangular interferometer with a standard polariscope has been proposed which will enable one to obtain normal photoelastic fringe pattern as well as the first derivative of the stress pattern from the same setup. The results under different conditions of testing are represented along with basic mathematical formulation for the same.
Radially graded - refractive index (GRIN) rod lenses have a number of advantages over conventional lenses in manipulating and processing the optical signals in optical fiber communication systems(1). In order to have a device using GRIN rod lenses, design requirements are varied in nature. A system containing one or more than one radial grin lenses or a combination of radial and axial GRIN dements is designed. The next step is to devdop the required GRIN elements with desired material properties. Finally, the system is optimised as a compromise between the ideal and real available GRIN elements. Ion exchange technique is the most widely used method to devdop GRIN profile in glass due to its simple instrumentation and ease of control. We have devdoped a novel method to predict the GRIN profile for a given set of experimental conditions (2). This method helps us in devdoping different types of GRIN profiles in the glass rods with minimum number of experimentation. After the glass rods have gone through the process of ion exchange, refractive index profile are measured in a set - up devdoped by us (3,4). In this paper, we present the development of radial GRIN rod lenses with a diameter of 1 to 2 mm. These GRIN rod lenses can be used for coupling of laser light source to the optical fiber.
A method for studying the stress-induced birefringence over the area of a sample by simultaneous application of shearing interferometry and moiré techniques is dealt with. This is a method by which one can have the fringe pattern for the first and second derivative of the birefringence distribution in the form of the slope and curvature of the test wavefront. There is, however, a method of obtaining the second derivative fringe system by using a four-exposure holographic technique in which the pattern is generated by shearing of two holograms of deformed surface. This is related to stress distribution in the structure under test. In the presented method, on the other hand, the test wavefront carries the information of stress distribution in terms of birefringence. The suggested experimental setup can provide the slope and curvature of the test wavefront in a single exposure.
We present a residue-based method in which the operations of decimal numbers of any magnitude can be processed using only two relatively prime moduli, 2 and 5. We suggest a method of implementation of addition and subtraction using different optical systems. Although the method suffers primarily from the difficulties associated with decimal carrying, we deal with these by means of a separate carry generator that can also be operated in parallel, thus reducing the number of steps.
In the present report several implementation of trinary logic functions using three logical values 1 0 and 1 will be presented. Fredkin gate having three input and three output lines has been suggested as a basic building block of an optical computer. In this paper a binary coded trinary (BCT) method has been used to represent each trinary number and several similar logic functions in blocks using Fredkin gates are proposed. I.