A new theory of Pockels birefringence in non-magnetic crystals

The linear birefringence induced in a crystal by the first power of an applied electric field E - the Pockels effect - is traditionally described by the index ellipsoid model and the impermeability tensor. An alternative approach is presented which, unlike the ellipsoid model, allows ready extension to explain other effects, such as optical activity. This approach shows that for certain crystal symmetries and field and light path directions, a second linear birefringence may be induced in addition to the Pockels birefringence, of comparable magnitude and having different fast-slow axes. Where it exists this Jones birefringence, as it is termed, would therefore be an undesirable accompaniment to the Pockels effect in an electro-optic device. Also undesirable would be any coexisting natural circular birefringence and the magnitude of this is compared with a Pockels birefringence in potassium dihydrogen phosphate (KDP).