ABSTRACT
This chapter shows that crystal optics involves a more complex situation than conductivity processes. The refractive index for the crystal will vary with direction. For tetragonal, hexagonal and trigonal crystals the indicatrix is an ellipsoid of revolution about the principal symmetry axis. This principal axis is called the optic axis and the crystals are said to be uniaxial. For orthorhombic, monoclinic and triclinic crystal systems, the indicatrix is a triaxial ellipsoid. The passage of light through crystals involves the propagation of transverse electromagnetic waves. External forces may arise from stress giving rise to the photoelastic effect, may be due to the application of an electric field giving rise to electro-optic effects, or due to a magnetic field giving rise to magneto-optic effects. For optical propagation in crystals, it is common to show the wave surface diagrammatically. The surface is different to both the indicatrix and the wavevector surface, although they are all directly related.
