Characteristic features of leaky surface acoustic waves propagating on liquid/piezoelectric film glass structures

Abstract

Particle displacement, electric potential distributions, velocity, and propagation loss for leaky surface acoustic waves (LSAWs) propagating on glycerine/ZnO or CdS film/Pyrex glass structures are studied theoretically and are compared with those of Rayleigh waves propagating on vacuum/ZnO or CdS/Pyrex glass structures. As a result it has been found, from the particle displacements, that the compressional waves are radiated into the liquid in the case of a LSAW. In particular, the power flow ratio in the liquid becomes nearly 100% when the ratio of the imaginary to the real part of the complex LSAW velocity becomes the same as that of the compressional wave. Such a phenomenon occurs for the glycerine/ZnO/Pyrex structure. On the other hand, a cut-off velocity exists for the glycerine/CdS/Pyrex structure, because the LSAW velocity lowers considerably with increasing CdS thickness, and approaches the compressional wave velocity of glycerine. The higher mode of LSAW is also found for the latter structure, and the difference between the higher and fundamental modes is discussed.