Binary geometric phase metasurface for ultra-wideband microwave diffuse scatterings with optical transparency.

Diffuse scatterings of electromagnetic (EM) waves by thin-thickness metasurfaces have promising prospects in many fields due to their abilities of significantly reducing the backward scatterings of targets. One of the major challenges is to further improve the working bandwidth. Here, we propose a binary geometric phase metasurface with high optical transparency to realize ultra-wideband backward scattering reduction through diffuse scatterings. A multi-layered reflective meta-structure is used as the basic building block while its out-of-phase counterpart is achieved through a geometric rotating operation. The proposed metasurface shows a polarization-insensitive wave-diffusion property with about 10 dB scattering reduction in an ultra-wide frequency band from 3.5 GHz to 16.6 GHz, reaching a fractional bandwidth of 130%. As the experimental demonstration, prototype is fabricated and measured that is in agreement with simulated results. The proposed metasurface provides an efficient way to tailor the exotic scattering features with simultaneously high optical transmittance, which can offer crucial benefits in many practical uses, for example, window stealth applications.