title: Orbital angular moment of a partially coherent beam propagating through an astigmatic ABCD optical system with loss or gain.
abstract: We derive the general expression for the orbital angular momentum (OAM) flux of an astigmatic partially coherent beam carrying twist phase [i.e., twisted anisotropic Gaussian-Schell model (TAGSM) beam] propagating through an astigmatic ABCD optical system with loss or gain. The evolution properties of the OAM flux of a TAGSM beam in a Gaussian cavity or propagating through a cylindrical thin lens are illustrated numerically with the help of the derived formula. It is found that we can modulate the OAM of a partially coherent beam by varying the parameters of the cavity or the orientation angle of the cylindrical thin lens, which will be useful in some applications, such as free-space optical communications and particle trapping.
authors.forename: Yangjian
authors.initials: Y
authors.lastname: Cai
authors.forename: Shijun
authors.initials: S
authors.lastname: Zhu