The higher-order coherence functions of optical fields involving phase fluctuations have not yet been studied extensively. We discuss here an experiment which can in principle yield the fourth-order coherence function. This experiment is a study of the correlation function of the irradiance fluctuations obtained in some interference experiments. Two kinds of delay are then used: optical delays in the interferometer and electrical delays with suitable variations in the correlator.
The results of the experiment are calculated theoretically with a particular statistical model of laser light. The possibility of using a spectrum analyzer instead of a correlator is discussed.
E. BOILEAU and B. PICINBONO, "Coherence Properties of Optical Fields. II. Study of Experiments Described by Fourth-Order Coherence Functions," J. Opt. Soc. Am. 58, 1238-1244 (1968)