Design of Inhomogeneous All-Dielectric Electromagnetic-Wave Diffusive Reflectarray Metasurface

In this letter, inhomogeneous, single-layer, all-dielectric, nonabsorptive 1-bit and 2-bit coding diffusive reflectarray metasurfaces for nearly uniform low-level electromagnetic wave diffusion under a wide range of incident angles (up to 60°) around 12 GHz are proposed. The proposed metasurface consists of a number of small-sized dielectric reflectarrays of unit cells exhibiting a parabolic reflection phase profile, i.e., focusing reflection phase, and these reflectarrays are distributed across the metasurface aperture according to optimized 1-bit and 2-bit coding sequences to ensure a low level of diffusive scattering in all directions in the half-space in front of the surface. The proposed metasurfaces are realized using all-dielectric unit cells of subwavelength periodicity to achieve the required reflection phase correction (and effective permittivity) at each unit cell inside the small-sized dielectric reflectarrays and to realize the coding particles of the 1-bit and 2-bit coding sequences. The final design metasurface is constituted by 4 × 4 small-sized dielectric reflectarrays, and there are 25 (5 × 5) dielectric unit cells in each reflectarray. The powerfulness of the presented diffusive reflectarray metasurface and its ability to achieve low-scattering field patterns under both normal and oblique incidence are demonstrated by means of full-wave simulations and experiments.