Tunable Geometric Fano Resonances in a Metal/Insulator Stack

TL;DR

This paper theoretically investigates tunable Fano resonances in a metal/insulator stack, revealing how material and geometric parameters influence mode coupling, lineshape asymmetry, and resonance features in the angular domain.

Contribution

It introduces a model for geometric Fano resonances in metal/insulator stacks, demonstrating tunability and lineshape reversal linked to system parameters and background radiation effects.

Findings

Resonance lineshape is tunable via material and geometric parameters.

Reversal of Fano lineshape asymmetry ( extit{q}-reversal) observed.

Resonance features are explained by surface plasmon polariton interactions.

Abstract

We present a theoretical analysis of surface-plasmon-mediated mode-coupling in a planar thin film metal/insulator stack. Solving for the modes of this structure, we obtain an avoided crossing in the angular domain that is tunable using the system's materials and geometrical parameters. The computed reflectance of the metal/insulator stack exhibits a lineshape that is modeled as a geometric Fano resonance, accompanied by a response function characteristic of an induced coherence, albeit in the angular domain. We also observe a reversal of the Fano lineshape asymmetry as the system's parameters are varied. We attribute this \emph{q}-reversal to an interloping background radiation field comprising the surface plasmon polariton mode.