Arbitrary wavefront modulation utilizing an aperiodic elastic metasurface

Metasurfaces have attracted much attention due to their much more compact configurations and their abilities to modulate wavefronts of propagating waves by abruptly shifting their phase and/or amplitude. Most current metasurfaces are usually composed of subunits with periodic unit cells, which limits their design freedom for arbitrary phase and amplitude modulation. To overcome this limitation, in this paper, we propose an aperiodic elastic metasurface where arbitrary phase and amplitude modulation can be achieved. The aperiodic elastic metasurface is composed of pillared resonators with different heights and an analytical model-based genetic algorithm (GA) inverse design method is employed to determine the heights of the pillared resonators. The underlying mechanism of the phase/amplitude shift and mechanism of full transmission are revealed. The proposed aperiodic elastic metasurface can steer and focus flexural waves with full transmission and can steer flexural waves into different directions with different amplitudes. The inverse design method and the aperiodic design in this paper can inspire the design of other types of functional metasurfaces for fascinating applications.