Plasmonic Fano Resonance in Homotactic Aluminum Nanorod Trimer: the Key Role of Coupling Gap

Recently, the Fano effect of aluminum nanostructures has attracted a lot of attentions in several detector and sensor applications, but the role of coupling gap in it remains unintuitive. In this paper, a homotactic aluminum rod trimer (HART) is designed to form the plasmonic Fano resonances and visualize the important role of coupling gap size. The plasmon hybridization model and far field images were used to qualitatively describe the formation mechanism of Fano resonance. The simulation results intuitively show that the Fano dip of HART with a smaller coupling gap size has a higher red-shift speed when increasing the refractive index of surrounding environment or the length of HART with a fixed axial ratio (LS/LL = 0.6). Our study provides the insights to the key role of coupling gap in the performance of Fano structures.