  Lamb waves with dominantly longitudinal displacement component have been
reported for sensor application in liquid media. However, they are still
limited for the fundamental symmetry mode with low plate
thickness-to-wavelength (h/l) ratio, resulting in large wavelength and low
resonance frequency. Here we show the finite element simulation study of
higher-order Lamb waves on GaAs and ZnO/GaAs plates. In-plane polarised
quasi-longitudinal higher-order Lamb waves are obtained at higher h/l ratio
resulting in higher resonance frequencies. The solid-liquid contact simulation
shows the confinement of acoustic energy inside the plate. The result
demonstrates the suitability of ZnO/GaAs higher-order quasi-longitudinal modes
for microsensor in liquid media.
