Angularly Dispersionless Scattering Patterns for Impenetrable Surfaces: A straightforward design based on transformation optics

Utilizing transformation optics (TO) methodology, we propose a feasible and straightforward approach to control the scattering pattern of impenetrable surfaces in the desired manner. As a great advantage not reported in previous studies, the presented coating layer can scatter multiple arbitrarily oriented beams whose directions are not affected by the frequency variation, namely as angularly dispersionless scattering. We benefit from the simplicity of classic geometrical optics (GO) as a design tool to avoid the complex procedure of the material derivation resulting from TO. Inspired by irregularities in rough surfaces, we propose a coating layer mimicking the scattering behavior of rough surfaces with high abilities to generate different far-field patterns with arbitrary beam numbers along the desired directions. Moreover, two interesting functionalities, i.e., anomalous reflection and retroreflection, are designed using the proposed coating layer. The material parameters of the proposed coating layer are numerically derived by solving the inverse Laplace equation. Our idea is further extended to design a scattering diffusion device with the quasi-isotropic pattern, which is applicable in radar cross-section reduction. As a demonstration, an anomalous reflector is implemented with an all-dielectric, lossless, and broadband coating layer. The experimental results are in good agreement with the numerical simulations.