Optical birefringence images of edge dislocations

Optical birefringence images of prismatic dislocation loops in gadolinium gallium garnet (Gd3Ga5O12 or GGG) are used to determine the conditions under which edge dislocations are invisible. The results confirm that edge dislocations with lines perpendicular to the optical axis are invisible when the polarizer or analyzer are parallel to the dislocation line. Copyright © 1976 WILEY‐VCH Verlag GmbH & Co. KGaA