Correlation lengths of thermal electromagnetic fields in equilibrium and out of equilibrium conditions.
Spatial coherence of thermal fields in far- and near-field zones generated by heated half-space into a vacuum is studied at essentially different thermodynamical conditions. It is shown that correlation lengths of fields in any field zone are different in equilibrium and out of equilibrium systems. In a wide range of distances from a sample surface, the correlation functions should be calculated using a total sum of evanescent and propagating contributions due to their mutual compensation at some conditions because of anticorrelations. It is demonstrated that correlation lengths as calculated with a proposed formula are in agreement with the behavior of correlation functions of thermal fields in the spectral range of surface excitations.
Illarion
I
Dorofeyev