Fano Resonances in Plasmonic Ring‐Disc‐Pair Systems

Abstract

Fano resonances in plasmonic nanostructures, generated by the spectral interference between a broad resonance or continuum and a narrow resonance, have attracted significant interest in recent literature. Herein, by introducing a nanodisc next to a nanoring via electron beam lithography, a set of Fano resonances for such a ring‐disc‐pair (RDP) hybrid is confirmed through coupling between the dipolar disc mode and different multipolar bonding ring modes. Furthermore, the influence of the RDP's geometric dimensions on the dark‐field scattering spectra is experimentally studied, indicating that the contrast ratio of Fano resonances can be improved by optimizing the ring/disc sizes and narrowing the gap in accordance with previous studies. The disc size can also control the spectral locations of these Fano peaks ranging from the visible to the near‐infrared regime. In addition, by comparing the Fano resonances among a series of ring/split‐ring/rod structures with varying curvatures coupled to a neighboring disc in simulations, it is demonstrated that the RDP presents stronger sensitivity for the same gap distance and shows high‐quality Fano resonances compared with more common disc‐inside‐ring cavities in literature.