  We review in this article the influence of surface waves on the thermally
excited electromagnetic field. We study in particular the field emitted at
subwalength distances of material surfaces. After reviewing the main properties
of surface waves, we introduce the fluctuation-dissipation theorem that allows
to model the fluctuating electromagnetic fields. We then analyse the
contribution of these waves in a variety of phenomena. They give a leading
contribution to the density of electromagnetic states, they produce both
temporal coherence and spatial coherence in the near field of planar thermal
sources. They can be used to modify radiative properties of surfaces and to
design partially spatially coherent sources. Finally, we discuss the role of
surface waves in the radiative heat transfer and the theory of dispersion
forces at the subwavelength scale.
