Flexible controls of scattering clouds using coding metasurfaces

Metamaterials or metasurfaces have been designed to precisely manipulate the scattering at every angle. Here, we propose to control the probability of random scattering appearing in the desired range of angles, which is defined in this letter as scattering cloud. We present a controllable random metasurface by simply adding a random coding sequence to gradient coding sequence. It is shown that the direction and size of the scattering cloud can be arbitrarily engineered. We demonstrate the exotic behavior of the scattering cloud by making an analogy to the electron cloud in quantum mechanics. A new coding particle featuring low-interference with neighboring coding particles is designed to realize the controllable random surface, which demonstrates highly consistent results to the theoretical calculations using fast Fourier transform. The exciting phenomena and versatile behaviors of scattering clouds and their probabilities enabled by controllable random surfaces will lead to diversified applications in the fields of electromagnetic waves and acoustic waves.