Configurations of the zero-birefringence and zero-dichroism lines of electromagnetic waves in weakly anisotropic crystals

Configurations of two types of lines—those of zero birefringence and zero dichroism—drawn by the end of the directional vector of the wave normal over the unit sphere, which correspond to the coincident phase velocities or the absorption coefficients of isonormal electromagentic waves in weakly anisotropic crystals, have been studied analytically. It is shown that under the conditions of weak dielectric anisotropy, even slight changes in anisotropy result in the dramatic deformation of the lines of both types. The corresponding evolution of the configurations with the change of the anisotropy parameters is considered by example of absorptive orthorhombic crystals.