Unified matrix representation for spin and orbital angular momentum in partially coherent beams

In this paper, the authors introduce and study a matrix formalism that allows describing the interplay between coherence and orbital angular momentum in partially coherent light beams. The matrix is an analog of the known coherence-polarization matrix, and can be combined with the latter to yield a general characterization of second-order correlations in stationary light fields of arbitrary polarization and orbital angular momentum.