Purcell factor of Mie resonators featuring electric and magnetic modes

TL;DR

This paper introduces a modal approach to accurately compute the Purcell factor in Mie resonators with electric and magnetic modes, revealing the importance of mode superpositions and providing insights into resonator design.

Contribution

It develops an analytic modal framework for calculating the Purcell factor in Mie resonators, accounting for both electric and magnetic resonances and mode superpositions.

Findings

The Purcell factor is often dominated by multiple modes rather than a single mode.

Translation-addition coefficients can predict effective volume features.

In doped silicon resonators, electric Purcell factor exceeds magnetic one.

Abstract

We present a modal approach to compute the Purcell factor in Mie resonators exhibiting both electric and magnetic resonances. The analytic expressions of the normal modes are used to calculate the effective volumes. We show that important features of the effective volume can be predicted thanks to the translation-addition coefficients of a displaced dipole. Using our formalism, it is easy to see that, in general, the Purcell factor of Mie resonators is not dominated by a single mode, but rather by a large superposition. Finally we consider a silicon resonator homogeneously doped with electric dipolar emitters, and we show that the average electric Purcell factor dominates over the magnetic one.