Ab initio theory of Fano resonances in plasmonic nanostructures and metamaterials

TL;DR

This paper develops an ab initio theoretical framework using Feshbach formalism to analyze Fano resonances in plasmonic nanostructures and metamaterials, highlighting the roles of electromagnetic modes and material losses.

Contribution

It introduces a general formula for asymmetric Fano resonances in non-conservative systems and links resonance features to electromagnetic interactions and material losses.

Findings

Intrinsic losses affect resonance contrast.

Coupling strength influences resonance width.

Analytical model matches numerical simulations.

Abstract

An ab initio theory for Fano resonances in plasmonic nanostructures and metamaterials is developed using Feshbach formalism. It reveals the role played by the electromagnetic modes and material losses in the system, and enables the engineering of Fano resonances in arbitrary geometries. A general formula for the asymmetric resonance in a non-conservative system is derived. The influence of the electromagnetic interactions on the resonance line shape is discussed and it is shown that intrinsic losses drive the resonance contrast, while its width is mostly determined by the coupling strength between the non-radiative mode and the continuum. The analytical model is in perfect agreement with numerical simulations.