Simultaneous determination of the sign and the magnitude of the topological charge of a partially coherent vortex beam

Abstract

Determination of the magnitude of the topological charge of a partially coherent vortex beam has been reported both theoretically and experimentally recently, while how to determine the sign of the topological charge of such beam remains unsolved. In this paper, we propose a simple method for simultaneous determination of the sign and the magnitude of the topological charge of a partially coherent vortex beam. This method is based on the measurement of the complex degree of coherence (CDOC) of a partially coherent vortex beam after propagating through a couple of cylindrical lenses. We find that the number of the bright fringes and the orientation of the distribution of the CDOC correspond to the magnitude and the sign of the topological charge, respectively. This phenomenon is confirmed by our experimental results.