Helicity‐Dependent Multifunctional Metasurfaces for Full‐Space Wave Control

Abstract Full‐space manipulation of electromagnetic waves with a thin flat plate is particularly intriguing for large‐angle scanning, functionality integration, and data capacity applications. However, majority of the designs to date are confined to linearly‐polarized wave operations; these render the versatile full‐space device operating under circularly‐polarized waves unaddressed due to the critical issue of the geometric phase being hardly decoupled among reflections and transmissions. Herein, a strategy for a helicity‐dependent multifunctional design by sandwiching dual‐layer geometric phase metasurfaces with a bandpass frequency selective surface is reported. The top and bottom metasurfaces are composed of two different types of meta‐structures, split ring resonators (SRRs) and a modified H‐shaped structure, which enable triple‐independent wavefronts at lower and upper frequencies (f₁ and f₂). At f₁, the top and bottom SRRs operate under reflection mode on both sides, and two distinctive wavefronts can be modulated by individually rotating the orientations of SRRs. However, at f₂, the modified H‐shaped structure operates in transmission geometry, and additional functionality can be independently modulated by changing their orientations. As a proof of concept, a multifunctional meta‐device is constructed with triple‐versatile functionalities. The approach followed in this study sets up a solid platform for arbitrary helicity‐dependent full‐space integrated devices.