Manipulating Coherence of Near-Field Thermal Radiation in Time-Modulated Systems

We show that the spatial coherence of thermal radiation can be manipulated in time-modulated photonic systems supporting surface polaritons. We develop a fluctuational electrodynamics formalism for such systems to calculate the cross-spectral density tensor of the emitted thermal electromagnetic fields in the near-field regime. Our calculations indicate that, due to time-modulation, spatial coherence can be transferred between different frequencies, and correlations between different frequency components become possible. All these effects are unique to time-modulated systems. We also show that the decay rate of optical emitters can be controlled in the proximity of such time-modulated structure. Our findings open a promising avenue toward coherence control in thermal radiation, dynamical thermal imaging, manipulating energy transfer among thermal or optical emitters, efficient near-field radiative cooling, and engineering spontaneous emission rates of molecules.

Automated summary

In this study, we demonstrate that the spatial coherence of thermal radiation can be manipulated in time-modulated photonic systems supporting surface polaritons. We develop a fluctuational electrodynamics formalism to calculate the cross-spectral density tensor of emitted thermal electromagnetic fields in the near-field regime. Our calculations indicate that time-modulation enables the transfer of spatial coherence between different frequencies and the possibility of correlations between different frequency components, which are unique to time-modulated systems. We also show that the decay rate of optical emitters can be controlled in the proximity of such structures, opening up avenues for coherence control in thermal radiation, dynamical thermal imaging, energy transfer manipulation, near-field radiative cooling, and the engineering of spontaneous emission rates.