Oscillator Chain: A Simple Model for Universal Description of Excitation of Waveguiding Modes in Thin Films

TL;DR

The paper introduces a simple oscillator chain model that provides a universal analytical approximation for Fano resonances in thin film micro-optical systems, capturing main properties and modifications.

Contribution

A novel simple mechanical equivalent model that mimics Fano resonances in micro-optical thin films, filling the gap of lacking universal analytical descriptions.

Findings

The oscillator chain model captures main properties of Fano resonances.

The model accounts for various modifications like amplification and non-Hermitian films.

Comparison with rigorous calculations shows good agreement.

Abstract

There is no simple and universal analytical description of various micro-optical systems related with Fano resonances. This especially concern modulated thin films, which, when coupled to external fields, show Fano resonances. Usually, such micro-optic circuits are simulated numerically, frequently by the use of commercial software. We fill this gap of the lack of universal analytical description by introducing and exploring a simple mechanical equivalent, the oscillator chain, which mimic such schemes involving Fano resonances. The model does not necessary provide the rigorous description of complicated micro-optical schemes, however does capture the main properties of such Fano-related micro-optical systems. The model captures different modifications of the thin film arrangement as well: thin film with amplification, non-Hermitical thin films, and others. It also covers the case of multiple Fano resonances in a thin film. The model is compared with the rigorously calculated (Rigorous Coupled Wave analysis) wave propagation in the thin films.