Surface acoustic wave coupling between micromechanical resonators

Abstract

The coupling of micro- or nanomechanical resonators via a shared substrate is intensively exploited to built systems for fundamental studies and practical applications. So far, the focus has been on devices operating in the kHz regime with a spring-like coupling. At resonance frequencies above several 10 MHz, wave propagation in the solid substrate becomes relevant. The resonators act as sources for surface acoustic waves (SAWs), and it is unknown how this affects the coupling between them. Here, we present a model for MHz frequency resonators interacting by SAWs, which agrees well with finite element method simulations and recent experiments of coupled micro-pillars. In contrast to the well-known strain-induced spring-like coupling, the coupling via SAWs is not only dispersive but also dissipative. This can be exploited to realize high quality phonon cavities, an alternative to acoustic radiation shielding by, e.g. phononic crystals.