金属-电介质纳米核壳结构的零背向散射特性

Zero-backward scattering by Metallo-Dielectric core-shell nanostructures

本文基于Mie散射理论,设计并研究了具有高定向、可调谐零背向散射特性的"金属-低介电-高介电"纳米核壳结构.分析了低介电层的厚度和折射率对偶极电、磁共振位置及强度的影响,发现将偶极电和磁共振在光谱上调节到重合,满足第一Kerker条件,可以实现零背向散射和显著增强的前向散射.进一步说明通过改变核壳结构的内核厚度和外半径或高介电层的折射率,能够实现零背向散射波长的可调谐.研究结果将对设计基于零背向散射的纳米结构和器件有重要的指导意义.

Based on the Mie theory, we propose and investigate a ＂metal （M）-low-permittivity （LP）-high-permittivity （HP）＂ core-shell nanoparticle that possesses the high directional zero-backward scattering characteristics. We analyze the effect of the LP layer on the wavelength and strength of the electric or magnetic dipolar resonance, and reveal that the zero-backward scattering and dramatically enhanced forward scattering are easy to be obtained by modulating the thickness and refractive index of the middle LP layer, which can engineer the dipolar electric and magnetic modes in the M-LP-HP core-shell nanoparticles to coincide spectrally with the same strength, thus satisfying the first Kerker condition of zero backward scattering. We also demonstrate that the zero-backward scattering can be tuned over a wide range from the near-infrared to visible by varying the metal core size and the outer radius of the HP shell or by changing the refractive index of the HP shell. Our results can provide a scientific direction for designing the nanostructures and devices based on the zero-backward scattering.