Epitaxially grown ferroelectric BaBi4Ti4O15 thin films were studied by optical second-harmonic (SH) generation using a femtosecond
titanium:sapphire laser at 800 nm wavelength. By varying both the
incidence and the azimuthal angle and registering the second-harmonic
intensity, a significant correlation was found between the azimuthal
dependence of the measured SH signal and the nanoscopic texture of the
samples, which was determined by electron microscopy and x-ray
diffraction. In particular, two different types of grains with
different crystallographic orientations generate different SH intensity
maxima with fourfold azimuthal symmetry, distinguishable from an
isotropic background due to a c-axis oriented main layer. This
correlation suggests the use of the SH technique for a purely optical
characterization of the film orientation and thickness. (C) 2002
American Institute of Physics.