Dual-Band Omnidirectional Invisibility of a Thin Slab with Antiscattering Coatings on Both Sides

Abstract

Making an object invisible means that an incident electromagnetic wave is not scattered with the object being present, which has been widely studied over the past few decades. Nevertheless, rendering omnidirectional invisibility for a large object in free space is still challenging. Here, we present a dual-band antiscattering coating using a double-layered metamaterial. By putting such coatings on both sides of a thin dielectric slab, omnidirectional invisibility is observed. It is shown that the peculiar double-layered metamaterial can provide electric polarization neutralization to the original thin slab, and the Maxwell Garnett mixing rule is safely invoked to guarantee the full elimination of scattering regardless of the incident angle. Full-wave simulations and experimental measurements exhibit that a composite made of a dielectric slab sandwiched by two antiscattering coatings can avoid any scattering in both the C and Ku bands with arbitrary incident angles. The proposed approach is quite simple and nondestructive to the original objects, which can be conveniently scaled to other scenarios including terahertz and optical applications, for boosting various internet of things devices, radar radomes, noninterference isolators in optics, and invisibility cloaks.