Hanbury Brown-Twiss effect and classical entanglement with OAM-carrying light

Abstract

We establish a decomposition of the intensity-intensity correlation of a scalar optical beam carrying orbital angular momentum (OAM) across multiple modes into intermodal contributions, thereby linking it, within the framework of the Hanbury Brown-Twiss effect, to the underlying modal coherence structure. Upon filtering the spiral phase dependence, the intensity correlations are governed by OAM coherence and orbital anisotropy reflecting classical entanglement between spatial and OAM degrees of freedom. These results extend intensity interferometry to structured light fields and provide direct access to modal coherence properties without phase-sensitive measurements.