Optical heterodyne detection of partially coherent cross-spectrally pure radiation is considered. A general formulation of the problem based on the photodetection statistics is presented first. Effects of temporal and spatial coherence of the signal on the heterodyne detection efficiency are then presented. Four limiting cases classified by the signal radiation coherence properties are considered in detail. The heterodyne antenna property, local oscillator (LO) laser requirement, and effects of radiation statistics on the heterodyne efficiency are also considered.
"Optical Heterodyne Detection Of Partially Coherent Radiation", Proc. SPIE 0194, Applications of Optical Coherence, (25 October 1979); doi: 10.1117/12.957920; https://doi.org/10.1117/12.957920