Strain enhancement of the electro-optical response in BaTiO3 films integrated on Si(001)

We discuss the possibility of significantly enhancing the nonlinear electro-optical response in strained perovskite BaTiO3. First-principles calculations predict the enhancement for both compressive and tensile strain. The physical origin can be traced to strain-induced phonon softening that results in diverging first-order susceptibility. Within the Landau-Ginzburg-Devonshire formalism we demonstrate how, in turn, this divergence results in a diverging second-order susceptibility and Pockels coefficient. Our results suggest a way to optimize BaTiO3 films for use in silicon nanophotonics.