Investigation of pseudo-Lateral-Field-Excitation in (yxl)-16.5° LiTaO3

In the present study, the LFE (lateral field excitation) coupling coefficient and phase velocity for (yxl)-16.5deg LiTaO3 were calculated as a function of the angle psi, which indicates the direction of the driving electric field with respect to the crystallographic x-axis of the piezoelectric plate. Several LFE devices of 5 MHz were designed and fabricated in two groups: psi = 0deg and psi = plusmn90deg. The result shows that for the LFE device of psi = 0deg operating in water, the thickness shear mode (TSM) could be excited both by LFE and TFE (thickness field excitation). For psi = plusmn90deg, the TSM is launched only by TFE and the device is in fact a pseudo-LFE device. Similar investigation has also been done to AT-cut quartz. The result suggests that the reported LFE AT-cut acoustic wave sensors may well be possible a pseudo-LFE device or a combination of TFE and LFE.