The optical anisotropy of the tetragonal phase of PbTiO₃ is discussed according to the point-dipole approach. In this microscopic model, we have taking into account of the electronic polarization and the lattice deformation, and it is shown that anisotropic electronic polarizabilities are the dominant source of the optical properties of PbTiO₃ . This anisotropy is attributed to the O_z oxygen ion and it is due to the Ti-Oz and Pb-Oz overlap in the tetragonal phase.

By analyzing the optical refractive index data of PbTiO₃ at 0.589 µm, we have determined the temperature dependence of the oxygen polarizabilities. Based on the dispersion data of the refractive index of PbTiO₃ , the dispersion of the oxygen polarizabilities is similarly calculated at room temperature.