Phononic Coupled-Resonator Waveguide Micro-Cavities

Phononic coupled-resonator waveguide cavities are formed by a finite chain of defects in a complete bandgap phononic crystal slab. The sample is machined in a fused silica plate by femtosecond printing to form an array of cross-shape holes. The collective resonance of the phononic cavities, in the Megahertz frequency range, are excited by a piezoelectric vibrator and imaged by laser Doppler vibrometry. It is found that well-defined resonant cavity modes can be efficiently excited, even though the phononic cavities are distant by a few lattice spacings and are only weakly coupled through evanescent elastic waves. The results suggest the possibility of engineering the dynamical response of a set of coupled phononic cavities by an adequate layout of defects in a phononic crystal slab.