Highly efficient transmissive wavefront steering with acoustic metagrating composed of Helmholtz-resonators

An acoustic metagrating composed of Helmholtz-resonators is demonstrated to control the propagation direction of acoustic waves. The transmissive acoustic wavefront steering is realized by simply modulating the geometric parameters of the resonators as well as the phase delay to coherently suppress the unwanted diffractions orders and to achieve the expected wave propagation. [Display omitted] •A kind transmissive acoustic beam steering is demonstrated by simply modulating the phase response of resonators in metagrating.•It is shown that the transmissive metagrating can be designed for the controlling of acoustic wave with classical Helmholtz-resonators.•The metagraing is well demonstrated in experiments forhigh-efficiency beam steering and the function can operate in a wide-angle range. Recently, a kind simply structured metasurface made of binary phase modulated meta-unit shows extraordinary beam steering functionality especially in the reflective beam manipulation. In this work, we demonstrate a Helmholtz-resonator based acoustic metagrating for high efficient beam wavefront steering in transmissive configuration. The complex meta-unit of the metagrating made of three Helmholtz-resonators combines traditional diffraction and interference theory with the free phase modulation ability of local resonant periodic structure to coherently control the acoustic wavefront steering. We show numerically and experimentally the anomalous refraction can be acquired with the designed metagrating of subwavelength thickness. By properly designing the geometric parameters of the meta-unit, the −1st order diffraction can be retained, and the unexpected diffraction orders are eliminated through destructive interference for a high efficient anomalous refraction. The anomalous refraction performance of the proposed metagrating is achieved over a wide incident range. The reported structure is promising for high efficient and wide angle complex wavefront engineering in e.g. encryption or communications.