Role of electric currents in the Fano resonances of connected plasmonic structures.

Marco Riccardi,Olivier J F Martin

doi:10.1364/oe.421951

Abstract

In this work, we use finite elements simulations to study the far field properties of two plasmonic structures, namely a dipole antenna and a cylinder dimer, connected to a pair of nanorods. We show that electrical, rather than near field, coupling between the modes of these structures results in a characteristic Fano lineshape in the far field spectra. This insight provides a way of tailoring the far field properties of such systems to fit specific applications, especially maintaining the optical properties of plasmonic antennas once they are connected to nanoelectrodes. This work extends the previous understanding of Fano resonances as generated by a simple near field coupling and provides a route to an efficient design of functional plasmonic electrodes.

Highlights

The design and fabrication of increasingly complex plasmonic structures is quickly becoming a key requirement to advance fields such as plasmonic and nanophotonic circuits [1,2,3,4,5], metamaterials [6,7,8] and sensing [1,7,8,9]
We start by studying the electrically connected antenna structure proposed in [43] and shown in Fig. 1, on the left. It is composed of a plasmonic dipole antenna connected to two nanorods which act as nanoelectrodes, feeding the antenna and allowing it to function as an emitter and receiver of optical radiation [12,44]
We can relate these dips to Fano resonances which originate from the coupling between the antenna’s dipolar bright mode [i.e. the black plot in Fig. 2(a)] and high-order dark modes in the electrodes, which are shown in green in Fig. 2(b) and appear as a result of Fabry-Perot types of resonances, as shown in Fig. S1, roughly at the same wavelengths as the dips

Summary

Introduction

The design and fabrication of increasingly complex plasmonic structures is quickly becoming a key requirement to advance fields such as plasmonic and nanophotonic circuits [1,2,3,4,5], metamaterials [6,7,8] and sensing [1,7,8,9]. It shows in blue, for different positions of the nanorods, the amplitude of the Fano resonance appearing in the far field spectrum of the connected structure around λ = 920 nm.

Results

Conclusion