Inverse Design of Diffusion-Absorption Hybrid Metasurfaces

Random metasurfaces have demonstrated significant potential in radar-signature control applications, but their ability to manipulate scattering-field reduction is limited by relying solely on the diffusion mechanism. To achieve flexible and arbitrary designs for scattering-field reduction, a diffusion-absorption hybrid metasurface is proposed based on the Babinet principle. This hybrid metasurface adopts complementary bilayer metasurfaces to satisfy the impedance matching condition and employs a hybrid absorption and diffusion mechanism. Such complementary designs' intralayer resonances and interlayer couplings are tailored by multi-objective optimization, achieving the precise and wideband design of absorptive elements with a specific reflection phase. By optimizing the spatial distributions of elements, diffusion is introduced and designs are achieved with a continuous scattering-field reduction from 15.40 to 32.58 dB at 15 GHz. Three representative designed structures are fabricated and verified as proof of concept. The experimental results are consistent with the calculations and simulations, demonstrating a 12.32-24.46 dB scattering-field reduction range. The proposed high-freedom metasurface and the implementation multi-objective optimization strategy collectively empower flexible wavefront manipulation, offering a viable solution for designing hybrid meta-devices that incorporate multiple mechanisms.