title: Directional Fano resonance in a silicon nanosphere dimer.
abstract: Fano resonance arising from the interaction between a broad "bright" mode and a narrow "dark" mode has been widely investigated in symmetry-breaking structures made of noble metals such as plasmonic asymmetric oligomers or other well-designed nanostructures. However, Fano resonance in nanoscale all-dielectric dimers has not been experimentally demonstrated so far. We report the first experimental observation of directional Fano resonance in silicon nanosphere dimers (both homodimer and heterodimer) and clarify that the coupling between magnetic and electric dipole modes can easily generate Fano resonance in all-dielectric oligomers, distinctly differing from conventional Fano resonances based on electric responses or artificial optical magnetism. A silicon nanosphere dimer, exhibiting a strong magnetic response inside and an electric enhancement in the gap, is an excellent structure to support magnetic-based Fano scattering. Interactions between magnetic and electric dipoles can suppress backward scattering and enhance forward scattering at Fano wavelengths. This directional scattering is much more prominent than that from a single silicon sphere and shows promising applications in areas such as directional nanoantenna or optical switching, opening up avenues for developing all-dielectric low-loss metamaterials or nanophotonic devices at visible wavelengths.
authors: Jiahao
authors: J
authors: Yan
authors: Pu
authors: P
authors: Liu
authors: Zhaoyong
authors: Z
authors: Lin
authors: Hao
authors: H
authors: Wang
authors: Huanjun
authors: H
authors: Chen
authors: Chengxin
authors: C
authors: Wang
authors: Guowei
authors: G
authors: Yang
keywords: Fano resonace; all-dielectric; directional scattering; magnetic response; silicon sphere dimer