A full-parameter unidirectional metamaterial cloak for microwaves

Abstract

Invisibility is a notion that has long captivated the popular imagination. However, in 2006, invisibility became a practical matter for the scientific community as well, with the suggestion that artificially structured metamaterials could enable a new electromagnetic design paradigm, now termed transformation optics. Since the advent of transformation optics and subsequent initial demonstration of the microwave cloak, the field has grown rapidly. However, the complexity of the transformation optics material prescription has continually forced researchers to make simplifying approximations to achieve even a subset of the desired functionality. These approximations place profound limitations on the performance of transformation optics devices in general, and cloaks especially. Here, we design and experimentally characterize a two-dimensional, unidirectional cloak that makes no approximations to the underlying transformation optics formulation, yet is capable of reducing the scattering of an object ten wavelengths in size. We demonstrate that this approximation-free design regains the performance characteristics promised by transformation optics.

Diffusive-light invisibility cloak for transient illumination

“…In addition, it is worth mentioning that a double carpet cloak transformation as the ones employed in Refs. [25,26] would not satisfy the unimodular condition, since its determinant is constant but different from unity.…”

Dc Magnetic Concentrator and Omnidirectional Cascaded Cloak by Using Only One or Two Homogeneous Anisotropic Materials of Positive Permeability

“…In addition, such a cascaded DC magnetic shielding device can also be easily achieved in the low frequency band (e.g., f = 200 kHz for metal detection), as meta-materials can easily give a permeability with 0 < µ < 1 in low frequency band. We should note that the cloak proposed in [24] is only for one specific direction. In the present paper, we propose an omni-directional cloak formed by cascaded shielding structures using two kinds of homogeneous anisotropic materials of positive permeability.…”

3D Visible‐Light Invisibility Cloak

“…Despite its elegance, the proposed general cloaking theory1, 2, 3, 4, 5, 6, 7, 8 is tremendously difficult to implement; as a result, all previous implementations have involved special cases 9, 10, 11, 12, 13, 14, 15, 16, 17, 18. The first experimental validation of an invisibility cloak was a 2D microwave cloak9 for single‐frequency transverse electric (TE) waves.…”