Experimental Realization of an Extreme-Parameter Omnidirectional Cloak

An ideal transformation-based omnidirectional cloak always relies on metamaterials with extreme parameters,which were previously thought to be too difcult to realize.For such a reason,in previous experimental proposals of invisibility cloaks,the extreme parameters requirements are usually abandoned,leading to inherent scattering.Here,we report on the frst experimental demonstration of an omnidirectional cloak that satisfes the extreme parameters requirement,which can hide objects in a homogenous background.Instead of using resonant metamaterials that usually involve unavoidable absorptive loss,the extreme parameters are achieved using a nonresonant metamaterial comprising arrays of subwavelength metallic channels manufactured with 3D metal printing technology.A high level transmission of electromagnetic wave propagating through the present omnidirectional cloak,as well as signifcant reduction of scattering feld,is demonstrated both numerically and experimentally.Our work may also inspire experimental realizations of the other full-parameter omnidirectional optical devices such as concentrator,rotators,and optical illusion apparatuses.