Near-Field Optical Physics

Interactions between objects separated by less than a wavelength form the basis of the emerging field of near-field physics. At these length scales information and energy can be transmitted through evanescent channels that are not available over longer distances. Spurred by the general bounds we have developed, we are pursuing novel manipulation of electromagnetic near fields. In our search to develop general design principles, one interesting result was an equivalence between seemingly unrelated structures: thin films, and hyperbolic metamaterials.

A critical application of near-field optics is to the field of radiative heat transfer, i.e. heat transfer mediated by photons, which has potential applications including thermophotovoltaics, radiative cooling of semiconductor chips, and more general thermal extraction. It has been known that greater-than-blackbody heat fluxes are possible, but the computational cost of simulating stochastic sources has prohibited consideration of all but the simplest designs. By a new energy-conservation approach, in conjunction with a multiple-scattering analysis and reciprocity principles, we have recently derived fundamental limits to near-field heat transfer, independent of shape–thereby defining, for the first time, what it means to be a “blackbody” in the near field. 

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