Long-scale decoherence and recoherence of partially coherent light in a graded-index waveguide

The nonparaxial propagation of partially coherent Gaussian Schell-model (GSM) beams in a graded-index waveguide is studied using the coherent states and coherent modes decomposition methods, as well as perturbation theory. Long-scale decoherence and recoherence of the GSM beam occur due to the revival effect caused by mode interference. It is shown that the radius of coherence and the degree of coherence can be determined based on measurements of purely geometric characteristics of the GSM beam. The information entropy and quantum mechanical purity of GSM beams are evaluated.