A hybrid invisibility cloak based on integration of transparent metasurfaces and zero-index materials

摘要

The invisibility cloak,a long-standing fantastic dream for humans,has become more tangible with the development of metamaterials.Recently,metasurface-based invisibility cloaks have been proposed and realized with significantly reduced thickness and complexity of the cloaking shell.However,the previous scheme is based on reflection-type metasurfaces and is thus limited to reflection geometry.In this work,by integrating the wavefront tailoring functionality of transparent metasurfaces and the wave tunneling functionality of zero-index materials,we have realized a unique type of hybrid invisibility cloak that functions in transmission geometry.The principle is general and applicable to arbitrary shapes.For experimental demonstration,we constructed a rhombic double-layer cloaking shell composed of a highly transparent metasurface and a double-zero medium consisting of dielectric photonic crystals with Dirac cone dispersions.The cloaking effect is verified by both full-wave simulations and microwave experimental results.The principle also reveals exciting possibilities for realizing skin-thick ultrathin cloaking shells in transmission geometry,which can eliminate the need for spatially varying extreme parameters.Our work paves a path for novel optical and electromagnetic devices based on the integration of metasurfaces and metamaterials.