Temperature control of thermal radiation from composite bodies

We demonstrate that recent advances in nanoscale thermal transport and temperature manipulation can be brought to bear on the problem of tailoring thermal radiation from wavelength-scale composite bodies. We show that such objects - complicated arrangements of phase-change chalcogenide (Ge2Sb2Te5) glasses and metals or semiconductors - can be designed to exhibit strong resonances and large temperature gradients, which in turn lead to large and highly directional emission at midinfrared wavelengths. We find that partial directivity depends sensitively on a complicated interplay between shape, material dispersion, and temperature localization within the objects, requiring simultaneous design of the electromagnetic scattering and thermal properties of these structures. Our calculations exploit a recently developed fluctuating-volume current formulation of electromagnetic fluctuations that rigorously captures radiation phenomena in structures with strong temperature and dielectric inhomogeneities, such as those studied here.