Birefringence images of screw dislocations viewed end on in cubic crystals containing a long-range stress field

Abstract

The expression for the intensity distribution and computer-simulated images of screw dislocations with Burgers vector α〈111〉 or α/2〈111〉 viewed end on in cubic crystals subjected to a long-range uniaxial stress has been obtained by considering the anisotropy of both elastic and photoelastic properties of the material. The computer-simulated images of end-on screw dislocations show twofold symmetry with a pair of dark and bright petals which result from the effect of a long-range stress superimposed on that of the screw dislocations. The computer-simulated images are in good agreement with the experimental images observed in Ba(NO3)2 and Gd3Ga5O12 crystals. The principal stress of the long-range uniaxial stress field around the screw dislocation in the crystal wafer has been estimated, based on this theory.