Acoustic holography using composite metasurfaces

Acoustic holography has emerged as a revolutionary technique to reconstruct the desired wavefronts of sound fields. Traditional acoustic holography typically relies on arrays of discrete sound emitters independently driven by sophisticated circuits to generate the required phase and amplitude profile. Recently, we witnessed growing efforts to conquer the realm of acoustic metasurfaces as a possible platform to reconstruct computer-generated holograms due to their advantages in manipulating sound waves with a well-controlled phase and/or amplitude. In this article, we review the latest efforts to explore an acoustic metasurface hologram in transmission-type and reflection-type systems, where we discuss how artificial meta-pixels appear as highly useful ingredients to tailor the flow of sound and transform a conventional incident wave into a desired arbitrary-complex wavefront in the far field. We summarize the latest advancements from their design principles to versatile functional applications, and some future research directions are also provided.