Quasi-Normal Mode Theory for Thermal Radiation from Lossy and Dispersive Optical Resonators

TL;DR

This paper introduces a comprehensive theoretical framework for understanding and designing thermal radiation from lossy, dispersive optical resonators, emphasizing mode loss matching and quasi-static resonant modes for optimized emission.

Contribution

A novel self-consistent formalism for thermal radiation from arbitrary lossy, dispersive optical resonators with a single dominant mode, guiding design for maximized emission.

Findings

Thermal emission is maximized when mode losses are matched.

Predominant resonant modes are electrically quasi-static.

Finite element methods efficiently calculate resonant modes.

Abstract

Although optical resonators are widely used for controlling and engineering thermal radiation, what has been lacking is a general theoretical framework to elucidate the thermal emission of optical resonators, and guide the design and application of thermally driven optical resonators. We developed a general and self-consistent formalism to describe the thermal radiation from arbitrary optical resonators made by lossy and dispersive materials like metals, with the only assumption that the resonators have a single predominant resonance mode. Our formalism demonstrates that the thermal emission of an optical resonator is maximized when the mode losses to the emitter and the absorber (or far-field background) are matched, and meanwhile the predominant resonant modes are electrically quasi-static. By efficiently calculating the resonant modes using the finite element methods, our formalism serves as a general principle of designing the arbitrary optical resonator thermal emitters with perfect or maximized emission.