Theories of cloaking

Naturally, some of the theories discussed here also employ metamaterials, either electromagnetic or acoustic, although often in a different manner than the original demonstration and its successor, the broad-band cloak.

Conceptually, a safecracker can enter a scene, steal the cash and exit, whilst a surveillance camera records the safe door locked and undisturbed all the time.

The concept utilizes the science of metamaterials in which light can be made to behave in ways that are not found in naturally occurring materials.

The distant observer only sees a continuous illumination, whilst the events that occurred during the dark period of the cloak's operation remain undetected.

[3] The idea of the event cloak was first proposed by a team of researchers at Imperial College London (UK) in 2010, and published in the Journal of Optics.

[3] An experimental demonstration of the basic concept using nonlinear optical technology has been presented in a preprint on the Cornell physics arXiv.

[5] This uses time lenses to slow down and speed up the light, and thereby improves on the original proposal from McCall et al.[3] which instead relied on the nonlinear refractive index of optical fibres.

These are lossless metamaterial covers near their plasma resonance which could possibly induce a dramatic drop in the scattering cross section, making these objects nearly “invisible” or “transparent” to an outside observer.

Low loss, even no-loss, passive covers might be utilized that do not require high dissipation, but rely on a completely different mechanism.

[11] These materials are further described as a homogeneous, isotropic, metamaterial covers near plasma frequency dramatically reducing the fields scattered by a given object.

A new research, of Kort-Kamp et al,[12] who won the prize “School on Nonlinear Optics and Nanophotonics” of 2013, shows that is possible to tune the metamaterial to different light frequencies.

Transmission of light (EM radiation) through an object such as metallic film occurs with an assist of tunnelling between resonating inclusions.

By creating and observing transmission peaks interactions between the dielectrics and interference effects cause mixing and splitting of resonances.

[17] Electromagnetic wormholes, as an optical device (not gravitational) are derived from cloaking theories has potential applications for advancing some current technology.

Although most progress has been made on mathematical and theoretical solutions, a laboratory metamaterial device for evading sonar has been recently demonstrated.

A theory has been developed for a cloak that could "hide", or protect, man-made platforms, ships, and natural coastlines from destructive ocean waves, including tsunamis.