Photoelastic characterization of ZnO films

The acoustooptic interaction between a light beam and acoustic modes propagating along a ZnO film, deposited on a Al₂O₃ substrate, has been utilized for analyzing the photoelastic properties of the film itself. The method relies on measurement of the intensity of the light scattered into the first diffraction order by different acoustic modes, for both s- and p-polarization of the incident light. Measurements performed on the first two acoustic modes supported by the film made it possible to determine the photoelastic constants p₁₁, p ₁₂, and p₁₃ of the ZnO film. The values obtained differ appreciably from those given in the literature for the bulk material. The measurements made it possible to determine the sign of the constants p₁₁ and p₁₂