Fabrication of Pb(Zr,Ti)O3 optical waveguide devices on silica substrate by metallo-organic decomposition

Preparation of PZT films on sapphire substrate applied to optical active devices, like switches, has been well developed over several years. Most integrated optical passive devices such as waveguide, coupler and array waveguide grating (AWG) are formed on the silica substrate. Integration of optical active and passive devices on the same silica substrates is extremely significant for planar lightwave circuits (PLC) employed in optical fiber communications. Ferroelectric PZT thin films deposited on single crystal substrates such as Sapphire, MgO and SrTiO₃ reveal excellent electro-optic properties. Notably, crack-free surface coatings were easy to achieve on single crystal substrates, while it is difficult to prepare thin film on amorphous substrates. In this study, we report the deposition of crack-free transparent PZT films (∼ 859 nm) on amorphous silica substrate utilizing SrTiO₃ buffer layer (∼257 nm) successfully. After annealing PZT films prepared by MOD processes using SrTiO₃ buffer layer textured growth is observed. Optical properties on textured films were measured via optical spectrometer. Although PZT films presented more absorption loss than silica materials, the oriented films demonstrated high electro-optic coefficient measured by Differential Transmittance Ellipsometry. By Effective Index Method (EIM), we can calculate an optimal range of relative refractive index between core layer and cladding layer of PZT material. On this basis, a single mode waveguide could be designed, and the distribution of light inside the waveguide could be simulated using Beam PROP software. In combining the photolithography and etching process to fabricate a PZT optical waveguide, the light propagation loss could be measured by IR capture of scattered light method.