2009/09/29 by Hui Feng, Hui Feng Ma, Wei Xiang Jiang +6 · 106 citations
Engineering · Materials Science · Physics and Astronomy · #Advanced Antenna and Metasurface Technologies #Antenna Design and Analysis #Broadband #Cloak #Computer science #Free space #Ground plane #Invisibility #Metamaterial #Metamaterials and Metasurfaces Applications #Optics #Physics #Telecommunications #Transformation optics #physics.class-ph #physics.optics
paper · pdf · open access · doi:10.1364/oe.17.019947
published in Optics Express 17(22), 19947 (Optica Publishing Group) · 14 pages, 4 figures
arxiv created 2009/09/29 · openalex publication_date 2009/10/19 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.