Transparent and Broadband Diffusion Metasurface With High Transparency and High Shielding Effectiveness Using Metallic Mesh

A novel transparent and broadband diffusion metasurface that is composed of digital coding elements is presented. A coding unit shares a symmetric circular quasi-Minkowski closed-loop shape that is capable of generating 1 bit coding (with two phase states of 0° and 180°) elements by using different geometric scales. To improve the optical transmittance of metasurface, the top layer of the coding elements adopts the metal rings with ultrathin linewidth with the optical transmittance of above 97% theoretically, whereas the bottom layer adopts hexagonal ring mesh metallic film with the optical transmittance of 95.4% and high electromagnetic interference (EMI) shielding effectiveness. Moreover, an optimized random distribution of coding elements is elaborately designed to realize diffusion patterns with numerous uniform grating lobes resulting in significant suppression of the backward peak energy level. Finally, a prototype diffusion metasurface is fabricated and good agreement between the simulated and the measured results is obtained. The results demonstrate a significant polarization-insensitive diffusion property with about 10 dB scattering reduction in a broadband from 10.5 to 19.5 GHz, reaching a fractional bandwidth of 60%, as well as show good scattering reduction properties for oblique incident waves. The proposed optical transparent diffusion metasurface has further advantages of opening up a new route for tailoring the exotic microwave scattering features with simultaneously high transmittance such as window and other transparent applications in visible frequencies and can be extended for imaging and communications.