Infrared and optical invisibility cloak with plasmonic implants based on scattering cancellation

In recent works, we have suggested that plasmonic covers may provide an interesting cloaking effect, dramatically reducing the overall visibility and scattering of a given object. While materials with the required properties may be directly available in nature at some specific infrared or optical frequencies, this is not necessarily the case for any given design frequency of interest. Here we discuss how such plasmonic covers may be specifically designed as metamaterials at terahertz, infrared, and optical frequencies using naturally available metals. Using full-wave simulations, we demonstrate that the response of a cover formed by metallic plasmonic implants may be tailored at will so that at a given frequency, it possesses the plasmonic-type properties required for cloaking applications.

Figure 1

(Color online) Geometry of a truncated (semi-infinite) planar composite material formed by a periodic array of nanolayers of silver embedded in a dielectric host. The truncated sample is illuminated by an incoming ${\text{TE}}^x$ plane wave.

Figure 2

(Color online) Permittivity as a function of frequency: Blue lines (associated with left-hand side scale): structured material; Black lines (associated with right-hand side scale): silver. The artificial material is formed by silver slabs with thickness $T=0.0374a$ which are spaced by $a=360\text{nm}$ and embedded in a host material with ${\epsilon }_h=6.5$.

Figure 3

(Color online) Virtual interface position $\delta$ as a function of the skin depth of the metal ${\Delta }_s$ at 100THz. The parameters $T$, $a$, and ${\epsilon }_h$ are as in Fig. 2. The inset illustrates the equivalence between a composite material slab with two adjoining dielectric layers with thickness $\delta$, and a continuous material described by the dielectric function (2).

Figure 4

(Color online) Peak in the scattering width $Q$ (normalized to arbitrary units) as a function of frequency, for different scenarios of interest. The inset represents a combined object-cloak system (the different parts of the cloak are not drawn to scale).

Figure 5

(Color online) Amplitude of the electric field for an object with (a) no cloak, (b) metamaterial cloak, (c) cloak with only metallic implants, and (d) dielectric cloak.

Figure 6

(Color online) Amplitude of the transmission coefficient (in dBs) for an array of cloaked objects illuminated by a plane wave (normal incidence). The distance between adjacent objects is $d$. The geometry is depicted in the inset.