Dispersion effects in thermal emission from temporal metamaterials: High-frequency cut-offs

TL;DR

This paper demonstrates that incorporating dispersion in the modeling of time-modulated materials introduces a high-frequency cut-off, resolving divergence issues and enabling accurate predictions of thermal emission spectra in temporal metamaterials.

Contribution

The work advances the theoretical understanding by integrating dispersive responses into models of time-varying photonics, revealing a natural high-frequency cut-off.

Findings

Divergence in emission spectra is due to non-dispersive assumptions.

Introducing dispersion removes high-frequency divergence.

Proper modeling enables accurate spectral predictions.

Abstract

The latest breakthroughs in time-varying photonics are fueling novel thermal emission phenomena, for example, showing that the dynamic amplification of quantum vacuum fluctuations, induced by the time-modulation of material properties, enables a mechanism to surpass the black-body spectrum. So far, this issue has only been investigated under the assumption of non-dispersive time-modulations. In this work, we identify the existence of a non-physical diverging behavior in the time-modulated emission spectra at high frequencies, and prove that it is actually attributed to the simplistic assumption of a non-dispersive (temporally local) response of the time-modulation associated with memory-less systems. Accordingly, we upgrade the theoretical formalism by introducing a dispersive response function, showing that it leads to a high-frequency cut-off, thereby eliminating the divergence and hence allowing for the proper computation of the emission spectra of time-modulated materials.