Spatial confinement of surface phonons in micro-resonators

In this work, we propose to exploit the interaction between surface acoustic waves (SAWs) and isolated, micron-scale mechanical resonators to strongly couple, confine and potentially store elastic energy at will. We theoretically and experimentally investigate the elastic features of a sample consisting in cylindrical pillars individually grown by focused ion beam induced deposition on a piezoelectric substrate. The pillars exhibit different geometrical parameters and are excited by a long-wavelength surface elastic wave. The obtained results highlight that waves propagating at the surface can trigger mechanical resonance of a micropillar that is in turn able to efficiently confine the impinging elastic energy despite its intrinsically strong coupling to the substrate. The proposed approach opens an interesting path toward dynamic control of surface phonons at the micro- or nano-scale.