High-efficiency transmissive invisibility cloaking based on all-dielectric multilayer frame structure metasurfaces.

Metasurfaces provide a completely new path to realize the cloaking effect due to their excellent electromagnetic wavefront manipulation. However, most previous metasurfaces realized cloaking by using phase compensation, which is limited by the reflection phase formula and can be used only for reflection mode. We use the generalized Snell's law to propose a free-space transmission stealth device, consisting of multilayer all-dielectric metasurfaces. We utilize three phase gradient all-dielectric silicon metasurfaces that, respectively, play the role of beam splitting, steering, and collection to guide incident waves around the object, thereby forming an ideal stealth area in free space. All-dielectric metasurfaces can greatly reduce transmission loss and enhance efficiency to a large extent. The advantage of choosing an all-dielectric material is that it is easy to process and more suitable in practice. Simulation results of the near field and far field prove that this cloak has a cloaking effect at 1 THz. Our work opens up a new path for transmissive stealth.

Enhancement of bandwidth and angle response of metasurface cloaking through adding antireflective moth-eye-like microstructure.

Ultrathin metasurface provides a completely new path to realize cloaking devices on account of their fascinating ability to control electromagnetic wave. However, the conventional cloaking devices are limited by their narrow bandwidth. To overcome this challenge, we present the realization of ultrabroadband and wide angle metasurface cloaking through high refractive index dielectric layer and antireflective "moth-eye-like" microstructure in this work. Two options are proposed and demonstrated numerically in terahertz region. By using local phase compensation, the proposed carpet cloaks can suppress significantly the unexpected scattering and reconstruct wavefront. The cloaking effects of the proposed design are verified from 0.65THz to 0.9THz with a wide range of angles. Moreover, the proposed metasurface cloaking is probable to extend to the optical and microwave domains and can be applied in stealth, illusion optic, radar and antenna systems.