SAW, PSEUDOSAW, and HVPSEUDOSAW in langasite

Langasite (LGS), like quartz is a trigonal class 32 material. It has been successfully grown and is generally considered to be very promising for surface wave devices since it has a larger electromechanical coupling than quartz and some zero temperature coefficients of frequency (TCF) and delay (TCD for saw) orientations have been found. Its detailed velocity, coupling, TCF, TCD, and power flow characteristics are not yet fully known and since there exist different sets of material constants in the literature there are significant differences in the properties predicted by different researchers. In this paper the focus is on the pseudosaw (PSAW) and high-velocity pseudosaw (HVPSAW) properties of some rotated cuts of LGS. In this paper the velocities, electromechanical coupling constants, and attenuation properties are described for various cuts for the SAW, PSAW, HVPSAW modes. Some low attenuation and high coupling cuts will be described. For rotated Y-cuts very low loss PSAW orientations are found whereas the HVPSAW attenuation is very high for all rotated Y-cuts. Some orientations where the PSAW velocity approaches the bulk fast-shear velocity asymptotically and the loss becomes insignificant over an appreciable range of angles, are also discussed