Transformation of modes of surface acoustic waves in strong KNbO sub(3) and PKN piezoelectric crystals

We consider the transformation of a generalized surface acoustic wave (GSAW) into a Bleustein-Gulyaev (B-G) or Rayleigh wave in the yx and 90-yx-cuts of rhombic KNbO sub(3) and orthorhombic PKN crystals in the case of slight deviation of the wave vector from the direction of the pure-mode axis. We have numerically analyzed the characteristics of the GSAW, B-G wave, and Rayleigh wave in the KNbO sub(3) and PKN crystals with strong piezoelectric coupling. It is shown that the GSAW has a mainly transverse component of the mechanical shift in the region of the yx cut. In this case, the electromechanical coupling coefficient has an unprecedented high value. We have analyzed the dependence of the distribution of mechanical shifts and electric potential of the wave propagating into the crystal on the distance from the substrate surface on the open and metallized surfaces; we also consider the dependence of the GSAW velocity in these crystals with variation in the metal film thickness.