Savaryn V. Methods of measurements of piezooptic coefficients and formation of polarization singularities at 2D stressed states

The relations describing the piezooptic effect are obtained and the method of measurements of piezooptic coefficients pikk (k = 4, 5, 6) is developed for crystals of all point symmetry groups and successfully tested on lithium niobate crystals. High accuracy of the method, which uses the four-point bending method, is demonstrated for determination of the value and sign of piezooptic and elastooptic coefficients and experimentally justified for K8 optical glass. Relations for the phase retardation and the angle of optical indicatrix orientation are derived for a disk compressed along its diameter. It has been found that at the propagation of optical beam through the opposite diametrical points of the disk the polarization singularities appear.