Asymmetric propagation using enhanced self-demodulation in a chirped phononic crystal

TL;DR

This paper reports on a novel asymmetric acoustic wave device using a chirped phononic crystal that combines nonlinear effects and dispersion to achieve efficient self-demodulation and strong non-reciprocity.

Contribution

It introduces a new design integrating nonlinear and filtering effects in a chirped phononic crystal for asymmetric wave propagation.

Findings

Up to 15% pressure amplitude of demodulated wave

Strong attenuation of undesired frequencies

Energy rectification ratio around 10^4

Abstract

Asymmetric propagation of acoustic waves is theoretically reported in a chirped phononic crystal made of the combination of two different nonlinear solids. The dispersion of the system is spatially dependent and allows the rainbow trapping inside the structure. Nonlinearity is used to activate the self-demodulation effect, which is enhanced due to the particular dispersion characteristics of the system. The main feature of the device is that integrates the nonlinear and the filtering effects in a single propagating medium. The performed numerical study reveals an efficient generation of the demodulated wave, up to 15\% in terms of the pressure amplitude, as well as strong attenuation for undesired frequency components above the cut-off frequency. The obtained energy rectification ratio is in the order of $10^4$ for the whole range of amplitudes employed in this work, indicating the robustness of the asymmetry and non-reciprocity of the proposed device for a wide operational range.