Second-order nonlinearity of wedge acoustic waves in anisotropic media

Guided acoustic waves localised at the apex of an infinite elastic wedge are influenced by second-order nonlinearity. This gives rise to a nonlinear term in the integro-differential equation describing waveform evolution at the apex of the wedge.On the basis of a representation of the displacement field in terms of Laguerre functions, this nonlinear term has been determined quantitatively for wedges made of silicon with various orientations and wedge angles. When comparing displacement gradients in the process of second-harmonic generation, the second-order nonlinearity of wedge acoustic waves is found to be in general smaller than that of Rayleigh waves in silicon, but can reach the same order of magnitude in certain propagation geometries.

► Second-order nonlinearity of wedge acoustic waves has been investigated. ► Its strength was determined quantitatively for wedge geometries in silicon. ► Values were computed of the kernel function in the nonlinear evolution equation. ► One of these values governs the strength of second-harmonic generation. ► The numerical data demonstrate a strong effect of anisotropy.