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

TL;DR

This paper presents the first experimental demonstration of broadband, low-loss free-space and compact carpet cloaks using non-resonant metamaterials, advancing practical invisibility applications in microwave frequencies.

Contribution

It introduces a novel design for broadband, low-loss cloaks that are more compact and feasible for real-world use, based on recent theoretical developments.

Findings

Successful experimental realization of broadband free-space cloak

Demonstration of a compact-sized carpet cloak with good invisibility

Cloaks operate effectively in microwave frequencies with low loss

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 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.