Integration of solution‐processed BaTiO3 thin films with high pockels coefficient on photonic platforms

The heterogeneous integration of ferroelectric BaTiO3 thin films on silicon (Si) and silicon nitride (SiN)-based platforms for photonic integrated circuits (PICs) plays a crucial role in the development of future nanophotonic thin film modulators. Since the electro-optic (EO) properties of ferroelectric thin films strongly depend on their crystal phase and texture, the integration of BaTiO3 thin films on these platforms is far from trivial. So far, a conventional integration route using a SrTiO3 template film in combination with high vacuum deposition methods has been developed, but it has a low throughput, is expensive and requires monocrystalline substrates. To close this gap, a cost-efficient, high-throughput and scalable method for integrating highly textured BaTiO3 films is needed. Therefore, an alternative method for the integration of highly textured BaTiO3 films using a La2O2CO3 template film in combination with a chemical solution deposition (CSD) process is presented. In this work, the structural and EO properties of the solution-processed BaTiO3 film are characterized and its integration into an optical ring resonator is evaluated. The BaTiO3 film exhibits a fiber texture, has a large Pockels coefficient (r(eff)) of 139 pm V-1, and integration into a ring resonator-based modulator shows a V pi L of 1.881 V cm and a bandwidth of > 40 GHz. This enables low-cost, high-throughput, and flexible integration of BaTiO3 films on PIC platforms and the potential large-scale fabrication of nanophotonic BaTiO3 thin-film modulators.