Cloaking mechanism with antiphase plasmonic satellites

In this work we theoretically demonstrate the possibility of cloaking a given object by surrounding it with a finite collection of suitably dimensioned, discrete “antiphase” plasmonic scatterers. It is shown that the total scattering from the object may approximately be canceled by the currents induced on a finite number of the plasmonic “satellite” scatterers, effectively making the whole system invisible to an external observer. Unlike other approaches, the proposed solution allows one to cloak a given object in a noninvasive manner since the antiphase satellites, being finite in number, do not need to fully cover and be in direct contact with the cloaked object.

Figure 1

(Color online) Geometry of the problem: a system formed by a dielectric cylindrical object and antiphase plasmonic scatterers (so-called satellites) illuminated by an incoming plane wave. The position and the material parameters of the satellites are optimized [using, for example, the genetic algorithm (GA)] to reduce the total scattering cross section from the whole system, inducing an effective cloaking mechanism.

Figure 2

(Color online) Total scattering linewidth $Q$ for a 2D system formed by a circular object and four antiphase satellites (see Fig. 1), as a function of the real part of the complex permittivity of the satellites, ${\epsilon }_s={\epsilon }_s^{\prime }+i{\epsilon }_s^{″}$, and different values of the loss tangent. Solid lines: full-wave results; dashed lines: analytical model. $Q$ is normalized to the scattering linewidth of the object standing alone in free space, $Q_0$. The object has permittivity ${\epsilon }_{\text{obj}}=4.0$ and diameter $D={\lambda }_0/6$. The radius of the satellites is $R_s=0.05D$ and the distance between the center of the object and the center of the satellites is $d=0.6D$.

Figure 3

(Color online) Total scattering linewidth $Q$ for a 2D system formed by a circular object and four antiphase satellites (see the inset) as a function of the real part of the complex permittivity of the satellites, ${\epsilon }_s={\epsilon }_s^{\prime }+i{\epsilon }_s^{″}$, and different values of the loss tangent. $Q$ is normalized to the scattering linewidth of the object standing alone in free space, $Q_0$. The dashed vertical line represents the solution obtained using the GA. The dashed (red) line represents the result obtained using the dipole approximation in the lossless case.

Figure 4

(Color online) (a): Distribution of the real part of the Poynting vector when a cylindrical object standing alone in free space is illuminated by a plane wave. (b): Similar to (a) but the object is cloaked with four antiphase satellites, whose geometry and material parameters have been optimized using the GA.

Figure 5

(Color online) Distributions of the amplitude of the total electric field for the same scenario as in Fig. 4.

Figure 6

(Color online) Radiation pattern in decibels (associated with scattered field) for different configurations of the considered system. The radiation patterns for the optimal configuration (blue line) and for an object isolated in free space (red line) are shown in both parts. (a): Radiation pattern for the case where the satellites are at the optimal distance from the object, but have nonoptimal dielectric constants ${\epsilon }_s=-125.0$ and ${\epsilon }_s=-75.0$. (b): Radiation pattern for the case where the satellites have an optimal dielectric constant, but are located at distance ${\delta }_s$ from the object different from the optimal distance ${\delta }_{s,\text{opt}}$.

Figure 7

(Color online) Total scattering linewidth $Q$ for a 2D system formed by a kite-shaped object and four antiphase satellites (see the inset) as a function of the real part of the complex permittivity of the satellites, ${\epsilon }_s={\epsilon }_s^{\prime }+i{\epsilon }_s^{″}$, and different values of the loss tangent. $Q$ is normalized to the scattering linewidth of the object standing alone in free space, $Q_0$. The dashed vertical line represents the solution obtained using the GA.

Figure 8

(Color online) Similar to Fig. 4 but for a kite-shaped object.

Figure 9

(Color online) Similar to Fig. 5 but for a kite-shaped object.

Figure 10

(Color online) Total scattering linewidth $Q$ for a 2D system formed by an elliptical object and eight antiphase satellites (see the inset) as a function of the real part of the complex permittivity of the satellites, ${\epsilon }_s={\epsilon }_s^{\prime }+i{\epsilon }_s^{″}$, and different values of the loss tangent. $Q$ is normalized to the scattering linewidth of the object standing alone in free space, $Q_0$. The dashed line vertical represents the solution obtained using the GA.

Figure 11

(Color online) Similar to Fig. 4 but for an elliptical-shaped object.

Figure 12

(Color online) Similar to Fig. 5 but for an elliptical-shaped object.