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arXiv 1303.0185physics.optics
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等离子体球中的非常规Fano效应和非共振场增强

Unconventional Fano effect and off-resonance field enhancement in plasmonic coated spheres

Tiago J. Arruda, Alexandre S. Martinez, Felipe A. Pinheiro

摘要:

我们研究了由色散等离子体核和电介质壳组成的涂层球的光散射。通过写的吸收截面的内部电磁场,我们证明了它是一个观察到的干扰,最终导致法诺效应的敏感。特别是,我们表明,非常规的法诺共振,最近发现的均匀球具有大的介电常数,也可以发生金属球涂有单电介质层。这些共振来自壳内具有相同多极矩的两个电磁模式之间的干涉,而不是来自粒子不同层的各种等离子体模式之间的相互作用。与均匀球体的情况相反,即使在瑞利极限下,涂层球体中也存在非常规的Fano共振。这些共振可以引起非共振场增强,其比用常规Fano共振实现的非共振场增强大约大一个数量级。我们发现,非常规和传统的法诺共振可以发生在相同的输入频率提供的色散核心具有负折射率。这导致粒子内部的最佳场增强,这一结果可能对等离子体激元的潜在应用有用。

英文摘要:

We investigate light scattering by coated spheres composed of a dispersive plasmonic core and a dielectric shell. By writing the absorption cross-section in terms of the internal electromagnetic fields, we demonstrate it is an observable sensitive to interferences that ultimately lead to the Fano effect. Specially, we show that unconventional Fano resonances, recently discovered for homogeneous spheres with large dielectric permittivities, can also occur for metallic spheres coated with single dielectric layers. These resonances arise from the interference between two electromagnetic modes with the same multipole moment inside the shell and not from interactions between various plasmon modes of different layers of the particle. In contrast to the case of homogeneous spheres, unconventional Fano resonances in coated spheres exist even in the Rayleigh limit. These resonances can induce an off-resonance field enhancement, which is approximately one order of magnitude larger than the one achieved with conventional Fano resonances. We find that unconventional and conventional Fano resonances can occur at the same input frequency provided the dispersive core has a negative refraction index. This leads to an optimal field enhancement inside the particle, a result that could be useful for potential applications in plasmonics.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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