Deposition and optical characterization of lead -based ferroelectric films for integrated optics

Abstract

Thin films of lead-based ferroelectrics have been grown by radiofrequency sputtering on various substrates for optical waveguiding purpose. The structure, the microstructure and the optical properties of the films have been studied as a function of the deposition parameters. Lead titanate (PbTiO3) has been grown in-situ on (100) SrTiO3 substrates under optimized conditions. At the temperature of 550°C, PbTiO3 films were completely c-axis oriented with a full width at half maximum (FWHM) of 0.26°. Lanthanum-modified lead titanate (Pb, La)TiO3 (28/0/100) have been prepared on (0001) sapphire with a post-deposition annealing of 600°C. For the optical characterizations, we have used the prism coupling technique. Refractive indices were found to be 2.61 and 2.37 at 632.8nm for respectively PbTiO3 and (Pb, La)TiO3 thin films respectively. Low optical loss of 2.2dB.cm−1 was evaluated in PbTiO3 waveguides. Electrooptic effects of PLT were investigated using the change of the resonant coupling angle induced by the refractive index variation with the electric field is applied. The linear electrooptic coefficient (r13) was about 55pm/V. These results illustrate the suitability of these materials for potential applications in integrated optics.