Theory of electrooptic effect in BaTiO3

The mechanism of electrooptic effect in BaTiO3 is discussed taking account of the dipole interaction among the constituent ions and their electronic polarizabilities. Three contributions are considered, namely; the first is caused by modified Lorentz correction for the dipole interaction, whose ratio to the whole contribution is estimated as 0.19; the second is due to the change of electronic polarizabilities due to the piezoelectric deformation, whose ratio is estimated as 0.81-(εclamp/εfree); the third contribution is related to the spontaneous Kerr effect, whose ratio is regarded as εclamp/εfree.