Acoustic Metagrating Holograms.

Abstract

Metasurface holograms represent a common category of metasurface devices that utilize in-plane phase gradients to shape wavefronts, forming holographic images through the application of the generalized Snell's law (GSL). While conventional metasurfaces focus solely on phase gradients, metagratings, which incorporate higher-order wave diffraction, further expand the GSL's generality. Recent advances in certain acoustic metagratings have demonstrated an updated GSL extension capable of reversing anomalous transmission and reflection, whose reversal is characterized by the parity of the number of wave propagation trips through the metagrating. However, the current extension of GSL has remained limited to one-dimensional metagratings, unable to access two-dimensional (2D) holographic images in three-dimensional (3D) spaces. Here, we investigate the GSL extension to 2D metagratings for manipulating waves within 3D spaces. Through our analysis, we experimentally demonstrate a series of acoustic metagrating holograms. These holographic images exhibit the unique ability to switch between transmission and reflection types independently. Our study introduces an additional dimension to modern holography design and metasurface wavefront manipulation. This article is protected by copyright. All rights reserved.