摘要
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.
基金
The authors thank P.Rebusco at Massachusetts Institute of Technology for critical reading and editing of the manuscript.Work in Zhejiang University was sponsored by the National Natural Science Foundation of China under Grants no.61625502,no.61574127,no.61601408,no.61775193,and no.11704332
the ZJNSF under Granta no.LY17F010008 and no.LY19F010015
the Top-Notch Young Talents Program of China,the Fundamental Research Funds for the Central Universities,and the Innovation Joint Research Center for CyberPhysical-Society.Work at Ames Laboratory was partially supported by the U.S.Department of Energy,Ofce of Basic Energy Science,Division of Materials Sciences and Engineering(Ames Laboratory is operated for the U.S.Department of Energy by Iowa State University under Contract no.DEAC02-07CH11358)
Te European Research Council under ERC Advanced Grant no.320081(PHOTOMETA)supported work at FORTH.