Optimal orientations of lithium niobate for resonator SAW filters

A criterion of simultaneous minimization of propagation loss at resonant and antiresonant frequencies, previously developed for optimization of rotated Y-cuts of LiTaO₃ (LT) used in resonator SAW devices, is applied to rotated Y-cuts of LiNbO₃ (LN). The optimal angle versus thickness dependence was determined for periodic gratings with Al, Cu, and Au electrodes. The main characteristics of LSAW, such as velocity, average propagation loss, electromechanical coupling factor and reflection coefficient, have been estimated along the optimal lines. In particular, it was found that propagation loss tends to zero in 76°YX cut with Al electrode thickness 0.055 wavelengths. Nonsymmetric orientations, which exist around symmetric cuts, were located and described in a simple relation between the Euler angles.