Optically transparent coding metasurfaces based on indium tin oxide films

We describe optically transparent coding metasurfaces based on indium tin oxide (ITO) thin films with high optical transparency and good electric conductivity. Four optically transparent coding metasurfaces are designed to realize desired scattering patterns. Three of them produce anomalous reflections for normally incident electromagnetic (EM) waves by encoding specific digital coding patterns. The fourth achieves diffusion-like scattering to reduce the backward radar cross section (RCS) by encoding an optimized random coding sequence. An ITO coding element based on a glass substrate is applied to reflect 0° and 180° phase responses. Based on this element, three coding schemes for beam deflection and one scheme for the RCS reduction are presented. The consistency of simulation and measurement results fully proves the powerful abilities of the optically transparent coding metasurfaces on manipulating EM waves. The center working frequency of metasurfaces is 12 GHz, in which the reflection beam angles of three schemes are 24.6°, 12°, and 36°, respectively. The diffusion-like scattering is verified by experiments, in which the RCS reduction is more than 10 dB. Considering the high-transparency property of the designed metasurfaces, we expect the proposed method to be exploited for many applications in the microwave and optical spectral ranges.