Broadband electromagnetic cloaking with smart metamaterials

Abstract

The ability to render objects invisible with a cloak that fits all objects and sizes is a longstanding goal for optical devices. Invisibility devices demonstrated so far typically comprise a rigid structure wrapped around an object to which it is fitted. Here we demonstrate smart metamaterial cloaking, wherein the metamaterial device not only transforms electromagnetic fields to make an object invisible, but also acquires its properties automatically from its own elastic deformation. The demonstrated device is a ground-plane microwave cloak composed of an elastic metamaterial with a broad operational band (10-12 GHz) and nearly lossless electromagnetic properties. The metamaterial is uniform, or perfectly periodic, in its undeformed state and acquires the necessary gradient-index profile, mimicking a quasi-conformal transformation, naturally from a boundary load. This easy-to-fabricate hybrid elastoelectromagnetic metamaterial opens the door to implementations of a variety of transformation optics devices based on quasi-conformal maps.

Terahertz carpet cloak based on a ring resonator metasurface

“…Many devices have been proposed based on metamaterials, ranging from lenses 3,4 and beam steering structures, 5 to cloaking devices [6][7][8][9] able to hide objects from an external observer. After years of intensive studies, several cloaking mechanisms and designs have been proposed, mostly among the two leading categories of transformation optics 10,11 and scattering cancelation [12][13][14] .…”

Reconfigurable photoinduced metamaterials in the microwave regime

“…We stress that reconfigurable photo-induced metamaterials in the microwave regime can offer significant potential to achieve novel electromagnetic multifunction applications such as, for example, dynamically photo-excited low reflection metamaterials and shielding panels [30], adaptive perfect lenses [31], active polarizers [24] and actively controllable cloaking devices [32].…”

Design and analysis of the trapeziform and flat acoustic cloaks with controllable invisibility performance in a quasi-space

“…While, the size of the cloaking shell is many times larger than the hidden object. 21 Zhang et al realized an acoustic cloak shell under water using transmission line theory experimentally. 22 But the design was complex and difficult.…”