Optically transparent (Pb,La)(Zr,Ti)O-3 (PLZT) thin films were sputter-deposited on SrTiO3(001) and MgO(001) substrates with a SrRuO3(110) bottom electrode. X-ray diffraction analysis showed epitaxial growth of monocrystalline PLZT, with (001) rocking curve full width at half maxima of similar to 0.03 degrees and similar to 0.3 degrees for films deposited on SrTiO3 and MgO, respectively. In-plane epitaxial alignment of the SrRuO3 and PLZT epilayers was verified from phi-scans. It was established from atomic force microscopy measurements that the PLZT surface roughness meets the requirement for optical waveguide applications. Recorded P-E loops for films grown on both substrates showed a remanent polarization of similar to 36 mu C/cm(2). The refractive index of the PLZT layer was estimated from rutile prism coupling measurements at similar to 2.56 for lambda=633 nm, consistent with data obtained by spectroscopic ellipsometry. The ferroelectric and optical characteristics of the films, as well as their surface roughness, were not appreciably different for the two substrates. This makes MgO the preferred choice of substrate for optical waveguide devices due to its low refractive index compared to that of SrTiO3.