Mode Evolution and Transmission Suppression in a Perforated Ultrathin Metallic Film with a Triangular Array of Holes

We theoretically study the evolution of the resonant modes and the transmission suppression (TS) effect in a perforated ultrathin metallic film (PUMF) with a periodic triangular array of holes. It is found that the properties of different resonances change as the hole radius increases, and the non-monotonic shift of resonant frequency can be interpreted qualitatively from the electric field distribution other than the Fano model. In addition, we analyze the strong mode interaction phenomenon in PUMF. When the diameter of holes approaches to four fifths of the lattice constant, the coupling between dipolar resonance and decapolar resonance can lead to an anticrossing and a large Rabi splitting, which is not available in PUMFs with square lattice; the resulting hybrid modes can be ascribed to the quasi-inphase and quasi-antiphase interferences between dipolar resonance and decapolar resonance. By comparing the TS effect of different resonances under different hole radii, we conclude that although dipolar resonance, short-range surface plasmons, and hybrid modes can all contribute to TS effect; the prominent TS effect in our structure should be mainly caused by the collective dipolar resonance of the structure. These findings might be of interest for the future studies in PUMF-based structures and devices.