Theory of Electro-Optic Response in Tetragonal BaTiO₃

The linear electro-optic (EO), or Pockels effect offers a promising path to fabrication of ultra-low power ultra-compact electro-optic modulators in silicon photonics bridging the optical technology with conventional silicon. Barium titanate, BaTiO₃ (BTO), has emerged as a promising electro-optic material that can be integrated with silicon photonics. In this talk, we report the first principles calculations of the EO or Pockels tensor in tetragonal BTO. Due to the lattice anharmonicity, predicting the Pockels response using functional theory (DFT) has been a challenge. However, our results indicate that the problem may be deeper. We show that the conventional P4mm structure of BTO is most likely a dynamic average of lower symmetry structures in agreement with recent experiments [1]. Using this argument as a starting point, we calculate both the ionic and piezo contributions of the EO tensor in good agreement with available experimental values.



[1] M. S. Senn et al. PRL 116, 207602 (2016)