The thermal far-field and near-field, where radiative heat transfer is mediated by bulk propagating waves and evanescent waves, respectively.

Polaritons and radiative heat transfer

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Description of Activities:

Polaritonic materials exhibit unique thermal emission properties with tailorable characteristics. In the near-field, for length scales in the nanometer range, thermally excited surface polaritons can carry thermal power density surpassing the blackbody limit, creating new pathways for molding the flow of heat.

Extracting and transferring thermal energy from macroscopic, bulk materials is limited by the incoherent and predetermined spectrum of thermal radiation. By contrast, in close proximity to a material’s interface, thermally excited photons in the form of evanescent excitations can carry thermal energy in unconventional ways including super-Planckian, narrowband, coherent, and even non-reciprocal thermal emission. Of such evanescent excitations, surface plasmon and phonon polaritons, occurring at frequencies that span the whole infrared range, are excellent carriers of thermal radiation. These can be found in plasmonic and polar materials in their bulk and thin-film forms, as well as in emerging monolayer-thick materials.

We are interested in various aspects of the polaritonic response of thin-films and low-dimensional materials such as their (i) prominent dielectric resonances, (ii) sensitivity to changes in their immediate dielectric environment, and (iii) optical anisotropies across all coordinate directions. We aim to leverage these characteristics for highly compact thermal emitters with reduced structural complexity that can serve various applications in renewable energy and storage, coherent thermal sources, contactless cooling, thermal regulation and camouflage.

G. T. Papadakis, A. Davoyan, P. Yeh, & H. A. Atwater, “Mimicking surface polaritons for unpolarized light with high-permittivity materials” Phys. Rev. Materials 3, 015202 (2019)