  Highly confined Love modes are demonstrated in a phononic crystal based on a
square array of etched holes in SiO 2 deposited on the ST-cut quartz. An
optimal choice of the geometrical parameters contributes to a wide stop-band
for shear waves' modes. The introduction of a defect by removing lines of holes
leads to the nearly flat modes within the band gap and consequently paves the
way to implement advanced designs of electroacoustic filters and
high-performance cavity resonators. The calculations are based on the finite
element method in considering the elastic and piezoelectric properties of the
materials. Interdigital transducers are employed to measure the transmission
spectra. The geometrical parameters enabling the appearance of confined cavity
modes within the band gap and the efficiency of the electric excitation were
investigated.
