Marc Reynaud, UT-Austin

"Orientation and Polarization Control of BaTiO3 Films for Applications in Si-Integrated Photonics"

Abstract: Silicon integrated photonics has emerged as a potential workaround for some of the bottlenecks seen in integrated electronics. However, silicon has one key flaw, in that it cannot modulate light easily on its own. The modulation of light is a crucial key in the design of photonic devices, and as such must be dealt with. While some methods to modulate light in silicon are possible, including the thermo-optic effect, plasmon dispersion effect, and strain yielding light modulation capabilities are possible, another method for modulation is placing different materials on the silicon for modulation. One such material is BaTiO3, which has one of the largest Pockel’s responses currently known. The Pockel’s response is the change in the refractive index of a material with respect to an applied electric field. It is a nonlinear effect and requires a noncentro-symmetric crystal. BaTiO3 is noncentro-symmetric, while silicon is not. Straining silicon produces a small response. With this being said, domain control of BaTiO3 is of crucial importance for device design for Si integrated photonics. The Pockel’s effect is an asymmetric property tied to the asymmetric refractive indices of a material, meaning that the refractive index of light is different when light impinges on the material in different directions. Therefore, in order to optimize BaTiO3 on for use in photonic devices, one must be able to control its domain 7 and polarization orientation. This is easier said than done. It is important to understand both the physics and materials science of the standard grown BaTiO3 on Si and using different methods to control its polarization such as applying large fields or using buffer layers. The work done here does just that, and hopefully provides insight for future graduate students to come