title: Comment on "partially coherent flat-topped beam and its propagation".
abstract: We point out that the expression of the cross-spectral density (CSD) of a partially coherent flat-topped beam (PCFB) given by Ge et al. [Appl. Opt. 43, 4732 (2004)] is incorrect. The results show that the M2 factor derived based on Ge's expression leads to M2 < 1 in some cases, which is physically unacceptable. A new expression of the CSD for a PCFB is given.
authors.affiliation: Coherent Reversible Atom Manipulation (CREAM) Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631, China.
authors.forename: Guohua
authors.initials: G
authors.lastname: Wu
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
authors.forename: Dongmei
authors.initials: D
authors.lastname: Deng