OAM-resolved source correlation-induced spectral changes in random light beams

Abstract

The phenomenon of the correlation-induced spectral changes (CISC) in the spectral density of a wide-stationary light beam is shown to occur for each component in its single-radius coherence-OAM (COAM) matrix, with the magnitude quantitatively depending on the OAM indices. As the diagonal elements of the COAM matrix are also radially resolved OAM spectrum components, the new effect may be viewed as the CISC in the OAM spectrum. Using the Gaussian Schell-model beam with the Gaussian spectral line, we then demonstrate the spectral shifts appearing on propagation in vacuum in its radially resolved OAM spectrum. We also prove the spectral invariance of the spatially integrated OAM spectrum.