Acoustic Convolution and Correlation and the Associated Nonlinearity Paramaters in LiNbO3

The parametric interactions of two oppositely propagating modulated acoustic surface waves can be used to produce acoustic convolution and correlation in YZ-cut LiNbO3 crystals in the 100–200-MHz range. Since the performance of these nonlinear devices depends critically upon the nonlinear properties of the materials used, the interaction is investigated in terms of the associated nonlinear free energy and the relevant expressions for the parameters are derived and also measured experimentally. The measured nonlinearity constants are K = 6.7 N/V m for convolution and Λ = 0.16×10−10 m/V for correlation. Several related factors are also discussed.