Transparent Bilayer ITO Metasurface with Bidirectional and Coherently Controlled Microwave Absorption

Abstract Metasurface absorbers (meta‐absorbers) are highly compelling in modern optoelectronic devices. However, owing to the limitations of the sandwiched design framework, conventional meta‐absorbers are restricted to fully absorbing only one‐sided incident waves while completely reflecting the electromagnetic (EM) waves from the opposite direction. In addition, the existing absorbers are opaque and their absorption performances are fixed after the initial design. Here, an optically transparent meta‐absorber consisting of bilayer indium tin oxide patterned layers that can achieve bidirectional and broadband absorption in the microwave frequency range is demonstrated. The inherent physics of bidirectional absorption can be attributed to the interference between multiple reflections and transmissions of EM waves. Furthermore, it is demonstrated that the absorption properties of the proposed meta‐absorber can be continuously switched via coherent control by adding another microwave beam to the other side of the meta‐absorber and manipulating the phase difference between the two input waves. The results indicate that the proposed design can enrich the functionalities of few‐layer metasurfaces and break new ground for EM shielding optical windows.