Acoustic asymmetric focusing lens by near-zero refractive index material

An acoustic asymmetric focusing lens based on a near-zero refractive index sonic crystal is studied,in which the left and right sides of the lens are vertical and circular planes,respectively.The acoustic wave which is incident from the side of the vertical plane surface can transmit through the lens and realize acoustic focusing with high performance.However,at the other side of the lens,the acoustic wave cannot pass through the lens with arbitrary incident directions,which arises from the direction selection mechanism of acoustic waves in near-zero refractive index materials.Therefore,the proposed lens can realize asymmetric transmission and focusing effects simultaneously.Besides,the focal length can be manipulated by changing the curvature radius of the lens,and the rigid scatterers inside the lens almost have no influence on the acoustic asymmetric focusing performance.The proposed lens has the advantages of multi-function,single type structure and high robustness,which provides theoretical solutions and experimental references for designing acoustic devices with asymmetric focusing effect based on near-zero refractive index materials.