Nonlinear electroacoustic interaction between a bias electric field and acoustic Lamb modes in LiNbO3 plates

[object Object]The change in phase velocity produced by a bias electric field on Lamb acoustic waves propagating along y z- and z y-LiNbO3 plates is analyzed here. This effect is interpreted theoretically in terms of the modifications produced by the bias field on the second-order material constants, under the approximation of small-amplitude acoustic waves superposed on a bias. According to this theory, these modifications are linked to the components of the bias field through combinations of second- and third-order material constants. Measurements performed on several Lamb modes lead to the determination of the effective second-order material constants in the presence of a bias field. The results obtained allow the evaluation of the electroelastic effect for acoustic propagation along any direction in the y z plane of the crystal, provided that the bias electric field lies in the same plane. In addition, these results give useful information on the nonlinear properties of the medium.