Diffraction spreading of surface waves on LiNbO3

The far-field diffraction spreading of surface acoustic waves on y cut LiNbO3, has been measured in two directions. For propagation along z, the beam is much narrower than for the isotropic case, and along a direction at 21.9° to z it is broader; both observations are in semiquantitative agreement with an analysis based on a parabolic approximation for the velocity surface in the neighbourhood of these directions.