Fast leaky surface acoustic waves on lithium niobate and lithium tantalate

The singularities of effective permittivity function for lithium niobate and tantalate are located in supersonic region and can be explicitly determined when a curved cut line is drawn from the longitudinal branch point. The singularities correspond to supersonic fast leaky waves. The supersonic fast leaky SAW exists on the ordinary YZ cut of lithium niobate. Due to the slowing and trapping effects under large mass and stress periodical loading these waves can be effectively generated by surface sources. Calculations of admittance characteristics of an infinitely long interdigital transducer show that the quality factor at resonant and antiresonant frequencies can attain several thousand of magnitude. The dispersion curves of these waves propagating in short and open circuited periodical systems of metal electrodes have been calculated