Therese Paoletta, UT-Austin

"Theory of the Electro-Optic Response in Titanate Perovskites"

Abstract: The linear electro-optic, or Pockels, effect measures how much an applied electric field changes the refractive index of light. This work focuses on two ABO₃ perovskites, barium titanate (BTO) and strontium titanate (STO), while others are already in practical use as Pockels devices, such lithium niobate (~30 pm/v). BTO has an exceptionally strong response (~1300 pm/V), and thus is an obvious subject of inquiry. We delve into the origins of its strong response by analyzing two phases, the low-temperature rhombohedral and room-temperature tetragonal. In another study, we pair experiment with theory to fully characterize a strain-engineered phase of BTO. Finally, we study the Raman spectrum of bulk, thin-film, and flakes of STO to investigate the effect film height has on the phonons. Throughout this work, phonons play a central role in the theoretical underpinnings of the response.