Nonlinear Coupling of Surface and Quasitransverse Bulk Modes in Cubic Crystals
R E. Kumon, M F. Hamilton
In some propagation directions in crystals, the speed of the surfaceacoustic wave mode may approach that of the lowest speed quasitransverse bulk mode. Under these circumstances, it is possible for energy to be transferred from the surface to the bulk mode by nonlinear coupling. In the present paper we investigate the possibilities for mode coupling in the (001), (110), and (111) planes of cubic crystals. A condition is given for determining the range of propagation directions with significant coupling, and numericalresults are provided for eight different crystals with a range ofanisotropy ratios. It is shown that even for significant excitationamplitudes the coupling is negligible for most propagation directionsin the aforementioned surface cuts.