Anisotropy in spatial correlations of thermal fields of heated samples of ZnSe

Abstract

Anisotropy in spatial coherence of thermal fields generated by the heated half-space of ZnSe radiating into a vacuum has been studied and is presented here. The frequency and distance dependencies of the coherence tensors of lateral and normal components of thermal fields are shown. Strong anisotropy in the near field zone is exemplified at different frequencies. It was confirmed that the coherence length within the frequency band of surface polariton excitations depends on the slope of the dispersion curve. The spatial coherence reaches the maximum degree at the initial part of dispersion curve and then is effectively suppressed at the frequency of quasi-static or Coulomb surface polariton. We also demonstrated that the smaller the distance from the surface, the smaller the correlation length of the thermal field up to the delta-correlated fields and their sources within the heated body. In the far zone, the anisotropy in the spatial coherences of components is much smaller than in the near field regime. The traces of the corresponding tensors in the far zone are calculated for the equilibrium and nonequilibrium problems.