title: Compact-sized and broadband carpet cloak and free-space cloak.
abstract: Recently, invisible cloaks have attracted much attention due to their exciting property of invisibility, which are based on a solid theory of transformation optics and quasi-conformal mapping. Two kinds of cloaks have been proposed: free-space cloaks, which can render objects in free space invisible to incident radiation, and carpet cloaks (or ground-plane cloaks), which can hide objects under the conducting ground. The first free-space and carpet cloaks were realized in the microwave frequencies using metamaterials. The free-space cloak was composed of resonant metamaterials, and hence had restriction of narrow bandwidth and high loss; the carpet cloak was made of non-resonant metamaterials, which have broad bandwidth and low loss. However, the carpet cloak has a severe restriction of large size compared to the cloaked object. The above restrictions become the bottlenecks to the real applications of free-space and carpet cloaks. Here we report the first experimental demonstration of broadband and low-loss directive free-space cloak and compact-sized carpet cloak based on a recent theoretical study. Both cloaks are realized using non-resonant metamaterials in the microwave frequency, and good invisibility properties have been observed in experiments. This approach represents a major step towards the real applications of invisibility cloaks.
authors.affiliation: State Key Laboratory of Millimeter Waves, Department of Radio Engineering, Southeast University, Nanjing 210096, China.
authors.forename: Hui Feng
authors.initials: HF
authors.lastname: Ma
authors.forename: Wei Xiang
authors.initials: WX
authors.lastname: Jiang
authors.forename: Xin Mi
authors.initials: XM
authors.lastname: Yang
authors.forename: Xiao Yang
authors.initials: XY
authors.lastname: Zhou
authors.forename: Tie Jun
authors.initials: TJ
authors.lastname: Cui
mesh_terms: D003198:Computer Simulation; D005430:Floors and Floorcoverings; D008027:Light; D008962:Models, Theoretical; D012031:Refractometry / Q000379:methods*; D012542:Scattering, Radiation