Birefringences: a challenge for both Theory and Experiment

The phenomenon of birefringence, the anisotropy of the refractive index induced in light when it impinges on matter subject to generally spatially inhomogeneous, electric and/or magnetic induction fields, is discussed. It is shown how the subject presents challenges for theory, computation and experiment. Examples are given for the Cotton–Mouton and Buckingham effects, and for magnetochiral, Jones and magneto-electric birefringences.