Enhancement of Fano resonance using modified trilayer fishnet metamaterials

Fano resonance (FR) is routinely observed in three dimensional(3D) symmetric metamaterials(MMs) consisting of elliptical nanoholes array (ENA) embedding through metal/dielectric/metal (MDM) multilayers. It is shown theoretically that a square periodic ENA perforating through MDM layers produces a FR response in the near infrared (NIR) regime. This FR response is attributed to the interplay between the bright modes and dark modes, where the bright modes originate from the electric resonance(localized surface plasmon resonance) caused by the ENA and the dark modes are due to the magnetic resonance(inductive-capacitive resonance) induced by the MDM multilayers. Notably, one can achieve a narrower FR when the elliptical nanoholes occupy the sites of a rectangular lattice, owing to the interaction of the magnetic resonances with the enhanced electric resonances. Moreover, a higher varying degree of the lattice constant along the horizontal direction allows for a FR with a higher value of the quality factor and the tuning of the amplitude and the resonant frequency of the transparency window. Such a FR created by the interference among the magnetic and electric dipolar resonances opens up an alternative way of forming a sharp FR in the symmetric multilayer MMs, and could be exploited for sensing.