A survey of isotropic and anisotropic modifications of the refractive index

Abstract

The effects causing differential modifications of the refractive index [MATH] are discussed. Isotropic changes are induced by the variation of the temperature and of the annealing schedule. Anisotropic changes can be caused by mechanical stresses and electric or magnetic fields. Simple dispersion formulae have been derived successfully on the basis of a one-term Sellmeier equation. It is shown that the experimental data can be fitted by these formulae. Further possibilities to vary [MATH] are mentioned.