Abstract
Direct interference between the orthogonal electric and magnetic modes in a hybrid silicon-gold nanocavity is demonstrated to induce a pronounced asymmetric magnetic-based Fano resonance in the total scattering spectrum at near-infrared frequencies. Differing from the previously reported magnetic-based Fano resonances in metal nanoparticle clusters, the narrow discrete mode provided by the silicon magnetic dipole resonance can be directly excited by external illumination, and greatly enhanced electric and magnetic fields are simultaneously obtained at the Fano dip.
Highlights
The light-metal interactions in subwavelength scale can produce localized surface plasmon resonance (LSPR) due to the collective oscillation of free conduction electrons on the metal surface [1]
Two sharp peaks at 1110 and 797 nm are originated from the magnetic dipole (MD) and the magnetic quadrupole (MQ) resonances respectively, while the broad one at 865 nm is ascribed to the electric dipole (ED) resonance [16,17,18]
To identify the character of a1 and b1 coefficients, the near-field distribution profiles in x-z and x-y planes corresponding to the MD and ED resonances are shown in the insets of Fig. 2(a)
Summary
The light-metal interactions in subwavelength scale can produce localized surface plasmon resonance (LSPR) due to the collective oscillation of free conduction electrons on the metal surface [1]. Symmetrybreaking is utilized as one method to activate the mutual interaction by breaking the orthogonality of the two modes Such metamaterials with engineered electric and magnetic resonances may enable many fascinating applications in nanophotonics, but the intrinsic losses and saturation effect strongly affect their overall performance at optical frequencies [16]. The dipolar electric and magnetic resonance modes in a single Si nanosphere as well as some other metamaterials like metal-semiconductor core-shell nanowires are noninteracting even though the near fields generated by the two modes can interfere, which can be observed in the forward and backward scattering spectra [16,19]. The asymmetric Fano line shape is replicated by calculating the probability to simultaneously excite the dipolar electric and magnetic resonances as well as their coupled state
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