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

Abstract

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.

Mechanisms of ultrasonic de-agglomeration of oxides through in-situ high-speed observations and acoustic measurements

“…The dynamic pressure as a result of shock waves (SW) and microjets arising from these attached bubbles as they undergo splitting and chaotic shape oscillations can reach up to 100 kPa [35] . Unlike intermetallics [26] , [27] , [28] , where the breakage mechanism occurred through the development and propagation of cracks resulting from the SW emissions, the breakage/de-agglomeration of agglomerates was primarily caused by either the gas bubbles present at the surface and within pores of the agglomerate (as also seen with the exfoliation of graphite in [39] ) or due to the pressure spikes in the vicinity of the bubble clusters released from the cavitation cloud formed below the vibrating horn producing the pulsations in subharmonics and ultra-harmonics observed in the frequency regime, which are related to the chaotic oscillations and collapse of the bubbly cloud as reported elsewhere [38] , [42] , [43] , [44] , [45] , [46] , [47] .…”

Acoustic, Phononic, Brillouin Light Scattering and Faraday Wave-Based Frequency Combs: Physical Foundations and Applications

“…In Section 5 , we review FCs obtained using the Brillouin light scattering effect [ 16 , 17 , 18 ], and we also demonstrate the possibility of increasing the amplitude of spectral peaks in the comb spectra by means of plasmonic resonant effects supported by metal nanostructures [ 19 , 20 ]. The discussion of the novel approaches to the generation of AFCs continues in Section 6 and Section 7 , where we review the recent advances in the fields of AFC generated using oscillations of gas bubbles in liquids [ 21 , 22 ] and vibrations of liquid drops [ 23 , 24 ], respectively. There, the reader will find a detailed analysis of both experimental and theoretical results [ 22 ] including those obtained using drops of room-temperature liquid metal alloys that have recently attracted significant attention in the fields of material science, electronics and optics [ 25 , 26 , 27 , 28 ].…”

Neural Echo State Network using oscillations of gas bubbles in water

“…Previously, we demonstrated that in a cluster of mm-sized bubbles with randomly-chosen equilibrium radii and initial spatial positions each bubble emits a unique acoustic signal that reflects a complex nature of its interaction with the neighbouring bubbles [30]. Furthermore, we suggested an acoustic frequency comb technique that can be used to reliably detect such signals [30,31]. Thus, a cluster consisting of N b randomly sized and positioned bubbles can be used as a reservoir network of N b × N b random connections, where the acoustic response of individual bubbles can serve as a physical counterpart of the neural activation states of ESN [2,6].…”

“…However, generation of microscopic bubbles requires special techniques [33]. Besides, microscopic bubbles are effectively stiffer than mm-sized ones [29] so that measurements involving them require special high-frequency and high-power ultrasonic equipment compared with a technically simple acoustic setup sufficient for studying mm-sized bubbles [31].…”

“…The bubble-based RC system has the potential to be optimised to complete forecasting tasks with higher accuracy, which could be achieved, for example, by following some of the steps used in the development of ESN [2]. Finally, we note that a relative technical simplicity of a potential hardware realisation of the bubble-based system and availability of techniques enabling one to experimentally resolve the response of individual oscillating bubbles in a cluster [30,31] should pave the way for proof-of-principle experiments.…”