Phononic crystal based tunable and nonreciprocal ultrasonic metamaterials

Abstract

Phononic crystals with asymmetric scatterers is an ideal platform to control the transmission of acoustic waves. These asymmetric scatterers has been used for nonreciprocal ultrasonic wave propagation in a fluidic medium due to the differential dissipation induced by the scatterers. The non-reciprocity of the wave-propagation depends significantly on the surface properties and the orientation of these individual scatterers. These quasi-periodic phononic structures with asymmetric scatterers can be used to modulate the propagation of the acoustic waves for an active acoustic insulator to a conductive behavior. The dispersion of the ultrasonic wave through the phononic crystal can be used to focus, beam-steer or filter the acoustic wave propagation as well as realize acoustical cavity for multifunctional applications. The localization of sound wave due to these orientation of the asymmetric scatterers has also been observed experimentally.