Nonlinear photonic crystals of BaTiO$_{3}$ and their electro-optic properties

Future optical systems will require electro-optic (EO) modulators with bandwidths of 100 GHz and low drive voltage. To achieve this, non-linear photonic crystals using epitaxial BaTiO$_{3}$ have been proposed. In our work two-dimensional photonic crystal (PhC) structures with a hexagonal array were fabricated from an epitaxial BaTiO$_{3}$ thin film using focused ion beam milling. The PhC waveguides were based on Si$_{3}$N$_{4}$/BTO/MgO multilayer epitaxial thin film structure. Simulation shows that sufficient refractive index contrast is achieved at 1550 nm to form a bandgap in the PhC structure by milling through the Si$_{3}$N$_{4}$ and BTO layers. The measured transmission spectrum of the PhC waveguide exhibited a stop-band centered at 1550 nm with well-defined band edges. Photonic crystal electro-optic modulators with a bandwidth of greater than 50 GHz have now been realized. The question of what dielectric properties limit the ultimate bandwidth of the PhC will be addressed.