Correlations between intensity fluctuations in stochastic electromagnetic Gaussian Schell-model beams

Recent researches about the vector theory of the Hanbury Brown-Twiss effect at optical frequencies have shown that a new statistical quantity, called the degree of cross-polarization, is needed to predict the correlations between intensity fluctuations in stochastic electromagnetic beams. This note is devoted to an investigation of the variations of the degree of cross-polarization and then to a comparison of the distributions of degree of coherence and the correlations between intensity fluctuations across the cross-section of stochastic electromagnetic Gaussian Schell-model (GSM) beams. Analysis leads to a generalization of scalar theory of the degree of global coherence that describes the GSM sources that generate the electromagnetic GSM beams of either spatially very coherent or spatially very incoherent in the global sense.