Abstract
Despite the fact that incandescent sources are usually spatially incoherent, it has been known for some time that a proper design of a thermal source can modify its spatial coherence. A natural question is whether it is possible to extend this analysis to electroluminescence and photoluminescence. A theoretical framework is needed to explore these properties. In this paper, we extend a general coherence-absorption relation valid at equilibrium to two non-equilibrium cases: luminescent bodies and anisothermal bodies. We then use this relation to analyse the differences between the isothermal and anisothermal cases and to study the near-field emission of an electroluminescent source.
Highlights
Light emission due to spontaneous emission by a thermalized ensemble of emitters is a priori expected to be spatially incoherent
In the non-equilibrium case, we considered only radiation emitted by the silicon carbide (SiC) and propagating away from it
Provided that the temperature and potential associated to excitation of a coupling mechanism are uniform over a given region, a simple reciprocity relation exists between the correlation of the fields emitted from this region by this coupling mechanism and the associated mixed losses. This generalized coherence-absorption relation gives access to the coherence properties of light emitted by sources by computing or measuring losses
Summary
Light emission due to spontaneous emission by a thermalized ensemble of emitters is a priori expected to be spatially incoherent. Previous experiments had shown how to take advantage of surface plasmons or guided modes to tailor the source directivity [3,8,9] All these experiments showing interferences or directivity reveal the presence of spatial coherence which can be fully characterized by the cross-spectral density tensor. For incandescent emitters at uniform temperature, the cross-spectral density tensor of the fields is directly proportional to the complex conjugate of the mixed losses [12]. This result has been discussed independently in the context. We use a spectral approach and assume an exp(−jωt) time dependency of the fields and currents
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