Anomalous electromagnetic scattering from radially anisotropic nanowires

We provide a full-wave electromagnetic (EM) scattering theory of discussing the electromagnetic scattering efficiency of radially anisotropic nanocylinders. In the long-wavelength limit, we derive the conditions for observing unusual EM scattering including non-Rayleigh vanishing and diverging ones. To verify our theoretical predictions, both full-wave numerical results and numerical simulations are performed, and good agreement is found. Moreover, physical origins of the anomalous phenomena are given. Therefore, the anisotropic nanowires under certain conditions can be hardly visible or exhibit superscattering. These results may find potential applications in different fields of nanotechnology.

Figure 1

Geometry of a radially anisotropic cylinder. The incident wave propagates in the direction of $\mathbf{k}$.

Figure 2

(a) Log-log plot of the scattering efficiency vs size parameter $q$. (a) ${\mu }_z=10$ (blue dotted line), ${\mu }_z=100$ (black solid line), and ${\mu }_z=1000$ (red dashed line). Other parameters are ${\varepsilon }_r=0.5$ and ${\varepsilon }_t=2$. (b) ${\mu }_z=1$ and $\sqrt{{\varepsilon }_r}\sqrt{{\varepsilon }_t}=1$ such as ${\varepsilon }_r=0.5$, ${\varepsilon }_t=2$ (blue dotted line), ${\varepsilon }_r=0.05$, ${\varepsilon }_t=20$ (black solid line), and ${\varepsilon }_r=0.005$, ${\varepsilon }_t=200$ (red dashed line).

Figure 3

The distribution of the magnetic fields both inside and outside of the anisotropic cylinder for ${\varepsilon }_r=0.5$ and ${\varepsilon }_t=2$ ($\sqrt{{\varepsilon }_r}\sqrt{{\varepsilon }_t}=1$) for Rayleigh behavior: (a) $q=0.001$ and ${\mu }_z=10$; (b) $q=0.0001$ and ${\mu }_z=10$. For non-Rayleigh vanishing behavior: (c) $q=0.001$ and ${\mu }_z=1$, (d) $q=0.0001$ and ${\mu }_z=1$.

Figure 4

(a) Log-log plot of the scattering efficiency vs size parameter $q$ for different parameters: (i) ${\varepsilon }_r=-0.5$, ${\varepsilon }_t=-2$, and ${\mu }_z=1$ (violet dotted line), (ii) ${\varepsilon }_r=-0.5$, ${\varepsilon }_t=-2$, and ${\mu }_z=10$ (black solid line), (iii) ${\varepsilon }_r=-2$, ${\varepsilon }_t=-0.5$, and ${\mu }_z=1$ (red dashed line), and (iv) ${\varepsilon }_r=-2$, ${\varepsilon }_t=-0.5$, and ${\mu }_z=10$ (green dashed and dotted line). Distributions of the magnetic field: (b) $q=0.001$ and (c) $q=0.0001$. Other parameters are ${\varepsilon }_r=-0.5$, ${\varepsilon }_t=-2$, and ${\mu }_z=1$.

Figure 5

The distribution of the electric [(a), (c), and (e)] and magnetic [(b), (d), and (f)] fields for $q=0.001$: (a) and (b) Rayleigh vanishing behavior for ${\varepsilon }_r=0.5$, ${\varepsilon }_t=2$, and ${\mu }_z=10$; (c) and (d) non-Rayleigh vanishing behavior for ${\varepsilon }_r=0.5$, ${\varepsilon }_t=2$, and ${\mu }_z=1$; and (e) and (f) non-Rayleigh diverging behavior for ${\varepsilon }_r=-0.5$, ${\varepsilon }_t=-2$, and ${\mu }_z=1$.