Compact-sized and broadband carpet cloak and free-space cloak

• Published in: Optics express Vol. 17; no. 22; pp. 19947 - 19959
• Main Authors: Ma, Hui Feng, Jiang, Wei Xiang, Yang, Xin Mi, Zhou, Xiao Yang, Cui, Tie Jun
• Format: Journal Article
• Language: English
• Published: United States 26-10-2009
• Subjects: Computer Simulation; Floors and Floorcoverings; Light; Models, Theoretical; Refractometry - methods; Scattering, Radiation
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/oe.17.019947

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.