  A quantum-mechanical formulation of energy transfer between closely-spaced
surfaces is given. Coupling between the two surfaces arises from the atomic
dipole-dipole interaction involving transverse-photon exchange. The exchange of
photons at resonance greatly enhances the radiation transfer. The spacing
(distance) dependence is derived for the quantum well - quantum well situation.
The interaction between two planar quantum wells, separated by a gap is found
to be proportional to the 4th power of the wavelength-to-gapwidth ratio and to
the radiation tunneling factor for the evanescent waves. Expressions for the
net power transfer, in the near-field regime, from hot to cold surface for this
case is given and evaluated for representative materials. Computational
modeling of selected, but realizable, emitter and detector structures and
materials shows the benefits of both near-field and resonance coupling (e.g.,
with 0.1 micron gaps).
