Ultra-wideband manipulation of electromagnetic waves by bilayer scattering engineered gradient metasurface.

Realizing effective scattering manipulation in broad operation band is a long pursuit. Here, we present an ultra-broadband metasurface to manipulate the scattering of electromagnetic waves based on spin-orbit interaction induced virtual shaping. The spin conversion efficiency is over 90% from 4.9 GHz to 22.8 GHz accompanied by a abrupt phase shift covering 0-2π, which is dependent on the orientation of the subwavelength of building blocks. Both Bessel- and triangular-type virtual profile shapes are developed for electromagnetic illusion and camouflage. Simulation and experimental results demonstrate that the significant backward RCS reduction of 10 dB is obtained from 5.5 to 22.5 GHz. The significant improvement in working bandwidth can be attributed to: the application of the dispersionless phase-shift properties of P-B phase, two-dimensional dispersion management methodology and catenary shaped local field enhancement in the metallic gap. The proposed design may have the potential applications in eletromagnetic manipulation and object detection.