Optical coherence properties of planar microcavity emission
  An analytical expression for the self coherence function of a microcavity and partially coherent source is derived from first principles in terms of the component self coherence functions. Excellent agreement between the model and experimental measurements of two Resonant Cavity LEDs (RCLEDs) is evident. The variation of coherence length as a function of numerical aperture is also described by the model. This is explained by a microcavity's angular sensitivity in filtering out statistical fluctuations of the underlying light source. It is further demonstrated that the variable coherence properties of planar microcavities can be designed by controlling the underlying coherences of microcavity and emitter whereby coherence lengths ranging over nearly an order of magnitude could be achieved. 
R. F. Oulton, P. N. Stavrinou and G. Parry