Geometry for plane-wave scattering by the concentric isotropic sphere.
Radar cross sections (RCSs) vs scattering angle (in degrees). Comparison of RCSs between a homogeneous double negative sphere in Ref. 35 and the concentric negative sphere where the mediums in regions 1 and 2 are set to be identical. The frequency of the incident wave is 6 GHz, the radii are chosen as and , and medium parameters are assumed to be . The sign of the imaginary parts is opposite to that in Ref. 35 due to the selection of time dependence.
SCS normalized by the factor of vs ratio of radius of inner core to the cover , where permittivity and permeability in the core are and , and those in the cover are and .
Normalized back-SCS vs radii ratio for Au nanospheres coated by different dielectrics at 441 THz, and different physical sizes of the coated sphere are considered: (a) electrically small , (b) medium , and (c) comparable to wavelength . The optical parameters of gold are obtained from Ref. 36.
Normalized back-SCS vs radii ratio for Au nanospheres coated by a low-permittivity cover and illuminated at 242 THz (solid line), 360 THz (dashed line), and 441 THz (dot-dashed line), respectively. Those gold nanospheres are coated by the same low-permittivity cover of . (a) electrically small , (b) medium , and (c) comparable to wavelength .
Normalized backscattering vs ratio of the radii for Au nanospheres coated by high-permittivity polymer at 242 THz (solid line), 360 THz (dashed line), and 441 THz (dot-dashed line).
Backscattering of DPS-DNG combinations for core-shell pairings in nanoscale.
Backscattering of ENG-MNG combinations for core-shell pairings in nanoscale.
Back-SCS vs at different nanosizes, when the cover is a Drude material working at the plasma frequency.
Backscattering vs incidence frequency for a two-layer particle at different nanosizes. The inner core is filled with ceramic and the cover is a Drude material. The frequency has been normalized by the plasma frequency . In (a), the outer radius is fixed at , and for (b). In each case, two core-shell ratios are considered, and the resonances are presented.
Backscattering of a three-layer nanoparticle with a Drude material sandwiched by ceramic, compared to the backscattering of a homogeneous Drude particle at the same outer radius . denotes the radius of the outermost spherical surface, while and still represent the two radii of inner shells.
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