Reflective acoustic jet generated by an engineered stepwise structure based on metagratings

In this work, we numerically investigate a reflective acoustic jet (r-AJ) generated by an engineered stepwise structure based on metagratings. First, the acoustic reflection characteristics of a periodic metagrating structure composed of isosceles right triangles are presented. Based on the reflective characteristics, a 2D stepwise structure is engineered to obtain special reflection by changing the size of the stepwise structure. Then, an axisymmetric stepwise structure is proposed for r-AJ generation. We find that the beam waist of the r-AJ produced by the axisymmetric stepwise structure has strong robustness against frequency fluctuations. Finally, we demonstrate that the proposed structure can work both in air and water environment by changing its size and the frequency of the incident wave.