Pockels effect in low-temperature rhombohedral BaTiO3

Abstract

We report a first principles analysis of the linear electro-optic (EO) or Pockels effect in rhombohedral $\mathrm{BaTi}{\mathrm{O}}_{3}$ (BTO), the lowest temperature phase of this ferroelectric perovskite. Si-integrated BTO is a promising material for EO modulators in Si photonics, with applications in optical quantum computing. This requires a fundamental understanding of the Pockels effect in BTO at low temperature. Through density functional perturbation theory, we explore the origins of a strong Pockels response by examination of the components that make up the ionic contribution to the EO tensor. We identify the phonon modes dominating the EO response and establish their relation to the electronic structure and optical properties of the material.