Acoustic interface waves in sandwich structures

We present a detailed analysis of acoustic interface waves in symmetrically embedded layers. In such systems generalized Lamb or shear vertical waves, polarized in the sagittal plane, and Love-type or shear horizontal waves, polarized perpendicular to the sagittal plane, can exist. The regions in the plane where these elastic interface waves can exist are discussed. The dispersion curves and the spatial dependence of the displacement fields of these acoustic phonon modes are calculated and presented in graphical form. These calculations were done for both, a general analysis in dependence of two different physical parameters and for two real systems, a Al-W-Al sandwich system and a Ga 1− x Al xAs-GaAs-Ga 1− x Al xAs double heterostructure. We show the possibility of the existence of Stoneley waves in the investigated layered systems in dependence of one of the two parameters. For the case that the speed of sound of the bulk transverse acoustic wave of the surrounding material is larger than that of the layer material, we have found that always an infinity of shear vertical waves localized within the layer exists.