2-bit amplitude-modulated coding metasurfaces based on indium tin oxide films.

Metasurfaces exhibit some extraordinary phenomena, resulting in their wide applications in controlling electromagnetic (EM) waves. Recently, the introduction of digital coding metasurfaces has greatly improved the design and broadened the application scope of metasurfaces. However, in most previous studies, the control of EM waves was achieved based on the phase distribution. Here, we present 2-bit amplitude-modulated coding metasurfaces based on optically transparent indium tin oxide films in the microwave frequency regime. The proposed coding metasurfaces are composed of coding unit cells with multiring structures with specific coding sequences, allowing the dramatic control of reflected amplitudes under the normal incidence while keeping other states unchanged. Using this method, almost continuous amplitude modulation can be easily realized with different coding sequences without the need to redesign the structure. The results of simulations and experiments show precise agreement, thereby validating the feasibility of our design. In addition, the optical transparency of the metasurface indicates its promise in a variety of microwave and visible-light applications. [ABSTRACT FROM AUTHOR]