The coherent-mode representation of arbitrary fluctuating optical fields is briefly reviewed and its application to the (non-lambertian) fields produced by the so-called gaussian Schell-model sources is discussed. The wavefields generated by lambertian sources are then analyzed within the framework of the coherent-mode representation. A simple and physically illustrative explanation is also obtained for the characteristic differences in the radiation properties of lambertian and spatially incoherent sources.
Ari T. Friberg,
"Coherent-Mode Representation Of Lambertian And Non-Lambertian Sources", Proc. SPIE 0473, Symposium Optika '84, (18 January 1985); doi: 10.1117/12.942431; https://doi.org/10.1117/12.942431