Numerical investigation of guiding of PSAW on quartz

The paper investigates guiding of low loss PSAW modes along the main axes of ST-cut quartz. It is well known that surface mechanical loading will influence properties as phase velocity and radiation losses of PSAW. Here we study how the distribution of the mechanical loading in the direction transverse to the main wave propagation will influence these parameters through guiding. This is investigated by a full wave theory, and for the X-direction in ST-cut also compared to the results from a scalar wave theory, which use analytical continuation of the wave slowness. This simpler theory is found to give results similar to the full theory, except for propagation losses in narrow wave guides, where it gives wrong results. Analytical continuation of the slowness data to obtain data where the real and imaginary part of the slowness are non-parallel is compared with full wave theory. Further the use of this in diffraction calculations is commented on