Attenuation and trapping of acoustic energy in composite microwave resonators based on YAG single crystals

The frequency dependence of acoustic wave attenuation in a composite piezoelectric microwave resonator is studied by acoustic resonance spectroscopy. In addition to the attenuation associated with the loss in the lattice, the diffraction loss, and the loss due to the scattering by the roughness of the reflecting faces, an extra attenuation component periodic in frequency is revealed. The appearance of this component is explained by the absence of acoustic energy trapping in the resonator within certain frequency intervals.