Acronym : PhoRest (Surface Coupled Phononic Resonators)
Abstract :

Schematic of the proposed measurement and excitation schemes for the characterisation of SAW - phononic resonator coupling. The resonators are excited by surface acoustic waves launched using an interdigital transducer. The resonator motion is characterized by laser scanning heterodyne interferometry. A scanning electron microscope image of a pillar pair fabricated by IBID is depicted in the inset.

Experimental observation of dipole states in paired phononic resonators excited along a diagonal incidence.

The PhoRest project aimed at the engineering of surface coupled phononic resonators for a increased control of phonon propagation and coupling. The overall objective was to push forward an original  conceptual approach to design complex systems that could contribute to the development of disruptive Information and Communication Technologies based on advanced acoustic signal processing functionalites.

In this context, we reported that resonator-surface coupling can be used to manipulate mechanical vibrations, reporting strong confinement of elastic energy in cylindrical pillars with dimensions of ten times smaller than the excitation wavelength or less. Individual resonators in ensembles could be addressed independently as a function of driving frequency, opening the door to coherent, high-frequency distribution and confinement of microscale elastic waves.

We then exploited this surface-to-resonator coupling further to demonstrate of a reciprocal platform allowing either to coherently control mechanical systems through SAW, or rather, to channel SAW propagation at the substrate surface through mechanical resonator coupling. Direct imaging of the vectorial nature of the interaction through optical interferometry indeed revealed the possibility to tune the mechanical coupling scheme. This, in turn, allowed controlling the resonator polarisation states, opening exciting perspectives for the implementation of SAW-driven, all-electromechanical information processing devices. The possible control of the strain distribution at the substrate surface also holds promises: outside SAW localization and waveguiding, the proposed platform could be used to trigger and control strain-mediated coupling, a mechanisms that has proven its relevance in optomechanical or nano-mechanical systems, but that also stands at the core of recent developments in nanomagnetism or spintronics.
Funding Agency : Agence Nationale de la Recherche, Programme JCJC (Jeunes Chercheurs Jeunes Chercheuses -- Young Researcher Programme).
Grant or funding obtained : 190 k€
Start and end dates : dec. 2014 - mar. 2019