Giant frequency down-conversion of the dancing acoustic bubble

Observation of Discrete Floquet Time Crystals in Periodically Driven Acoustic Bubbles

We show experimentally and theoretically that the translation dynamics of acoustic bubbles in an acoustic standing wave field exhibit all the attributes of a discrete time crystal, the dynamics of which is described by Mathieu’s equation. Individual bubbles and synchronized bubbles in a self-organized chain undergo emergent slow persistent oscillations. The period of the emergent oscillations is longer than that of the driving acoustic wave by three orders of magnitude, therefore, breaking the discrete time translation symmetry of the driver.

Acoustic frequency combs using gas bubble cluster oscillations in liquids: a proof of concept

We propose a new approach to the generation of acoustic frequency combs (AFC)-signals with spectra containing equidistant coherent peaks. AFCs are essential for a number of sensing and measurement applications, where the established technology of optical frequency combs suffers from fundamental physical limitations. Our proof-of-principle experiments demonstrate that nonlinear oscillations of a gas bubble cluster in water insonated by a low-pressure single-frequency ultrasound wave produce signals with spectra consisting of equally spaced peaks originating from the interaction of the driving ultrasound wave with the response of the bubble cluster at its natural frequency. The so-generated AFC posses essential characteristics of optical frequency combs and thus, similar to their optical counterparts, can be used to measure various physical, chemical and biological quantities.