Near-Field Effects in Spatial Coherence of Thermal Sources
Résumé
We present an exact calculation of the cross-spectral density tensor of the near field thermally emitted into free space by an opaque planar surface. The approach, based on fluctuational electrodynamics and the fluctuation-dissipation theorem, yields novel near-field correlation properties. We show that the spatial coherence length of the field close to the surface at a given wavelength lambda may be much smaller than the well-known lambda/2 of blackbody radiation. We also show that a long-range correlation may exist, when resonant surface waves, such as surface-plasmon or surface-phonon polaritons, are excited. These results should have important consequences in the study of coherence in thermal emission and in the modeling of nanometer scale radiative transfer.
Domaines
Optique [physics.optics]
Origine : Fichiers éditeurs autorisés sur une archive ouverte
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