1 Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China; 2 State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
Abstract We report an acoustic focusing lens composed of two-layer annuluses made of metal cylinders in air. We find that the cylindrical waves can be focused into a perfect point without diffraction in the centre of the annuluses, which arises from the Mie-resonance modes in the annuluses. The focusing frequencies are related to the size of the inner annulus, and the focusing effect can be applied to the annuluses with different shapes and incident positions. Interesting applications of the focusing lens in the acoustic beam splitter and directional transmitter with energy enhancement are further discussed.
Fund: Project supported by the Major Program of the National Natural Science Foundation of China (Grant No. 51239005), the National Natural Science Foundation of China (Grant No. 11404147), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20140519), the China Postdoctoral Science Foundation (Grant No. 2015M571672), the Research Fund for Advanced Talents of Jiangsu University, China (Grant No. 11JDG118), and the Training Project of Young Backbone Teachers of Jiangsu University, China.
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