# On the Calculation of the Quality Factor in Contemporary Photonic Resonant Structures

## TL;DR

This paper evaluates various numerical methods for accurately calculating the quality factor in modern photonic and plasmonic resonant systems, highlighting their limitations due to material dispersion and light leakage.

## Contribution

It provides a comparative assessment of common $Q$ calculation methods and identifies their applicability limits in complex contemporary photonic structures.

## Key findings

- Q calculation is complex in plasmonics and 2D materials due to dispersion and leakage.
- Different methods have specific applicability ranges depending on system properties.
- The work serves as a practical reference for accurate $Q$ evaluation in photonic research.

## Abstract

The correct numerical calculation of the resonance characteristics and, principally, the quality factor $Q$ of contemporary photonic and plasmonic resonant systems is of utmost importance, since $Q$ defines the bandwidth and affects nonlinear and spontaneous emission processes. Here, we comparatively assess the commonly used methods for calculating $Q$ using spectral simulations with commercially available, general-purpose software. We study the applicability range of these methods through judiciously selected examples covering different material systems and frequency regimes from the far-infrared to the visible. We care in highlighting the underlying physical and numerical reasons limiting the applicability of each one. Our findings demonstrate that in contemporary systems (plasmonics, 2D materials) $Q$ calculation is not trivial, mainly due to the physical complication of strong material dispersion and light leakage. Our work can act as a reference for the mindful and accurate calculation of the quality factor and can serve as a handbook for its evaluation in guided-wave and free-space photonic and plasmonic resonant systems.

---
Source: https://tomesphere.com/paper/1902.09415