  The optical properties of lead zirconate titanate (PZT) thin films deposited
on ZnO were studied by m-lines spectroscopy. In order to retrieve the
refractive index and the thickness of both layers from the m-lines spectra, we
develop a numerical algorithm for the case of a two-layer system and show its
robustness in the presence of noise. The sensitivity of the algorithm of the
two-layer model allows us to relate the observed changes in the PZT refractive
index to the PZT structural change due to the ZnO interface of the PZT/ZnO
optical waveguide.
