Design rules for active control of narrowband thermal emission using phase-change materials

TL;DR

This paper introduces an analytical framework for designing actively tunable narrowband thermal emitters using phase-change materials, enabling large spectral shifts and high ON-OFF switching at infrared frequencies.

Contribution

It provides a general design methodology for active narrowband thermal emitters with phase-change materials, applicable to various mechanisms and without lithography.

Findings

Near-unity ON-OFF switching demonstrated

Large spectral shifts between emission wavelengths achieved

Design is angle-independent and broadly applicable

Abstract

We propose an analytical framework to design actively tunable narrowband thermal emitters at infrared frequencies. We exemplify the proposed design rules using phase-change materials (PCM), considering dielectric-to-dielectric PCMs (e.g. GSST) and dielectric-to-metal PCMs (e.g. $\mathrm{VO_2}$). Based on these, we numerically illustrate near-unity ON-OFF switching and arbitrarily large spectral shifting between two emission wavelengths, respectively. The proposed systems are lithography-free and consist of one or several thin emitter layers, a spacer layer which includes the PCM, and a back reflector. Our model applies to normal incidence, though we show that the behavior is essentially angle-independent. The presented formalism is general and can be extended to \textit{any} mechanism that modifies the optical properties of a material, such as electrostatic gating or thermo-optical modulation.