Abstract
Manipulating acoustic waves beyond the diffraction limit offers alternative possibilities to many applications in wave physics. Here, we show that a gradient-index acoustic metasurface is able to achieve this purpose by modulating airborne sound at subwavelength scales via the local-resonance-controlled spoof surface acoustic waves. From the dispersion relation of such a surface mode, a design approach of explicitly correlating the effective refractive index with the geometrical unit-cell parameters can be obtained. With one carefully designed gradient-index acoustic metasurface constructed using locally resonant elements, we demonstrate the experimental realizations of both subwavelength plane-wave sound focusing and super-resolution acoustic imaging. This work provides a feasible pathway to the subwavelength manipulation of airborne sound. Moreover, it offers an ideal experimental platform to directly observe how acoustic energy flow is governed by refractive-index modulation. The proposed design approach can be easily applied to various spoof surface acoustic wave devices that demand gradient index distribution.
Original language | English |
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Article number | 034061 |
Journal | Physical Review Applied |
Volume | 11 |
Issue number | 3 |
DOIs | |
Publication status | Published - 26 Mar 2019 |
ASJC Scopus subject areas
- General Physics and Astronomy