Cloak for multilayered and gradually changing media

Electromagnetic Detection of a Perfect Invisibility Cloak

“…Perfect cloaking is believed to be undetectable at its working frequency because a perfect cloak is equivalent to a curved but empty EM space. Although the first cloak models can achieve invisibility only in a very narrow frequency band [3,13], efforts to extend the bandwidth are currently proceeding [9][10][11][12]14]. While it is well known that nothing can hide from a pulse detection covering the whole frequency spectrum [15], the possibility of realizing invisibility cloaking within a nonzero bandwidth has great significance on both theoretical and practical levels and has attracted a lot of attention from scientific community.…”

“…Therefore, the dyadic Green functions take different forms accordingly. Here, we derive the dyadic Green functions in the physical space directly, whose solution can be extended to consider both loss [6] and dispersion [13].…”

The effect of electrostatic shielding using invisibility cloak

“…When the total charges tend to zero, no field can go out of the cloak which is in complete agreement with the result for an active source inside the cloak as its radiation frequency goes to zero. 12 The behavior of electrostatic shielding of the cloak is identical with a spherical conducting shell in the screened area no matter where the sources are located, inside or outside the cloak. However, the electric fields in the source-existing area are different between the two systems.…”

“…In cylindrical cloak, the tangent component of magnetic field B φ → ∞ at the inner surface r = a of cloak, and the integral d While, for the ideal case of the shielding phenomenon, the normal component of electric field E r becomes a delta function compressed on the interface and contributes to the surface voltage ψ = − a+0 a−0 E r dr. 12 In the sense of dielectric materials, the surface voltage is caused by the infinite electric polarization of the material with ε rr = 0 on the interface. 12 However the surface voltage and the shielding effect of charges can also be caused by the the surface magnetic current in the dual superconductor. As we all known, the Meissner effect says that a superconductor expels magnetic fields from its interior and therefore the equivalent permeability of superconductor is equal to zero.…”

“…3,4 The effectiveness of transformation based cloak with passive objects inside has been verified through ray tracing approach, 5,6 fullwave simulations, 7 and analysis based on scattering models. [8][9][10][11] On the other hand, the case that active sources are located inside the hidden area has also been investigated both in physics 12 and mathematical senses. 13 These investigations revealed the ideal invisibility cloak at particular frequency can prevent the electromagnetic waves generated by the sources inside the cloak from propagating out, meanwhile an extra surface electric and magnetic voltage are induced by the infinite polarization on the inner surface.…”