Quasi-Three-Dimensional Angle-Tolerant Electromagnetic Illusion Using Ultrathin Metasurface Coatings

Low-profile and light-weight coatings that offer comprehensive manipulation of the electromagnetic scattering for finite-length objects are highly desirable, but not yet achieved, for applications including camouflaging, deceptive sensing, radar cognition control, and defense security. Here, for the first time, the theory, practical design, and experimental demonstration of quasi-three-dimensional and angle-tolerant electromagnetic illusion coatings are presented which have been enabled by ultrathin single-layer functional metasurfaces. By controlling the multiple Mie scattering coefficients using the tangential and non-vanishing radial electromagnetic responses of the metasurface, the quasi-two-dimensional coating transforms the electromagnetic perception of one object to mimic that of another which has been pre-selected by the designer. The illusion coating, which is homogeneous but anisotropic, is realized using hundreds of composite electric and magnetic sub-wavelength unit cells operating at frequencies away from their resonance. Two different prototypes of the metasurface illusion coatings were fabricated and characterized, demonstrating very good camouflaging performance for finite-length dielectric as well as conducting objects within a field-of-view up to +/-10 degrees off normal. This work paves the way for practical artificially engineered material coatings with exotic and versatile scattering control capabilities that would enable a wide range of applications throughout the entire electromagnetic spectrum.