Effects of Periodic Structures on the Coherence Properties of Blackbody Radiation Field

The coherence properties of blackbody radiation in homogeneous media have been studied extensively [1–5]. Research has shown that there is coherence in the blackbody radiation field and has given an estimation of the coherence length. The coherence length is often used as an indication of whether phase information needs to be considered when dealing with transport phenomena [6–8]. Generally, the wave packets can be treated as particles if the size of the transport domain is larger than the coherence length. An example is the optical ray tracing method, which is based on intensity superposition of electromagnetic waves and neglects any phase information. The wave optics method, in contrast, includes the phase information. Past research on single layer thin films have shown that the ray tracing method can be used when the thickness of the film is larger than the coherence length [7, 8]. However, this paper shows that the conventional coherence length may not be a sufficient criterion to validate the ray tracing approach in multilayer structures. Figure 1 shows a multilayer structure with one side subjected to blackbody radiation from a 1000K source. In the present study, two non-absorbing layers of the same thickness but different indices of refraction alternate to form the multilayer structure.