Integrated PLZT thin film waveguide modulators

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Abstract
In this paper we report field-induced spatial variations of outcoupled light in integrated ITO/PLZT/SiO2/Si and ITO/PLZT/SiO2/GaAs waveguiding structures, where the SiO2 layer acts as a buffer layer between the semiconducting substrates and PLZT, facilitating the support of TE and TM waveguide modes. Analysis of the various TE and TM modes is achieved using a prism out-coupling method. An electric field applied transversely to the propagation direction using the transparent ITO electrode induces a change in the effective indices of the waveguide modes which in turn causes an angular variation in the prism out-coupled modes. We have demonstrated an angular shift as large as 0.5° with a calculated field strength of 300 V/mm. The angular variation in the films display a quadratic relation to the applied field. The observed modulation can be explained in terms of a change in the effective index due to electro-optic effects in the PLZT film and/or possibly electrostrictive effects in the film layers.