Some properties of the higher-order coherence functions of optical fields are reviewed. A few experiments on light, beat, and interference are discussed by using the fourth-order coherence functions. The higher-order coherence functions of the amplitude-stabilized laser are derived by assuming the gaussian process for the phase fluctuations.
B. PICINBONO and E. BOILEAU, "Higher-Order Coherence Functions of Optical Fields and Phase Fluctuations," J. Opt. Soc. Am. 58, 784-789 (1968)