High-coupling leaky surface acoustic waves on LiNbO ₃ or LiTaO ₃ thin plate bonded to high-velocity substrate

The propagation properties of leaky surface acoustic waves (LSAWs) and longitudinal-type LSAWs (LLSAWs) on a LiNbO 3 (LN) or LiTaO 3 (LT) thin plate bonded to an AT-cut quartz or c -plane sapphire ( c -Al 2 O 3 ) substrate with a high phase velocity were investigated. It was theoretically revealed that when the LN or LT thin-plate thickness is less than one wavelength, the particle displacement of LLSAWs was concentrated in the thin plate and the electromechanical coupling factor ( K 2 ) was increased to two to three times that in the single substrate. Furthermore, for 36° Y -cut X -propagating LT/ c -Al 2 O 3 with an LT thin-plate thickness of 0.35 λ and X -cut 36° Y -propagating LN/ c -Al 2 O 3 with an LN thin-plate thickness of 0.19 λ, the values of K 2 for an LSAW and an LLSAW were experimentally found to increase from 5.6 and 10.4% in the single substrate to 11.5 and 19.7% in the thin-plate bonded structure, respectively.