The behavior of quasi-longitudinal leaky surface waves in crystals

A numerical analysis of non-leaky surface waves propagating in crystals at the supersonic velocity has been performed. These waves were found to be composite bulk waves (CBWs), in general three-partial and comprising incident quasi-longitudinal and two reflected quasi-transverse bulk modes. A projection of the subspace, in which the CBW satisfies the stress-free boundary condition, was calculated for orientations of LiNbO/sub 3/, defined by the Euler angles (90/spl deg/, 90/spl deg/, /spl psi/). The angle /spl psi/=163.3/spl deg/, for which CBW satisfies both mechanical and electrical boundary conditions, agrees with known propagation direction for non-leaky wave, and the angular dependence of velocity for CBW is very close to that of leaky waves, when the surface is nonmetallized. Application of the same technique to quartz cuts (0/spl deg/,/spl theta/,/spl psi/) gave the lines of supersonic non-leaky waves. These lines include exceptional waves, which correspond to degeneration of the three-partial CBW into one-partial exceptional wave.