Electro-optic effect in hexagonal compounds RFeO₃

The linear electro-optic effect is investigated in films of RFeO₃ compounds (R = Y, Lu, Yb) possessing hexagonal symmetry. A general equation for the optical indicatrix of the film at arbitrary orientation of an external electric field is derived. The equation of the indicatrix in the principal axes, as well as the principal refractive indices, are determined for the particular case of an external electric field orientation along the [010] axis. Two novel optical axes are identified in the presence of an electric field. It was determined that two isonormal modes propagate in the film when light propagates along the [100] direction. The refractive indices associated with these modes were also found. The phase shift associated with the propagation of these modes and caused by the presence of an electric field is calculated. The shift is linear along the electric field, thereby demonstrating the Pockels effect.