Non-axial nature of an optical vortex and Wigner function

Before we use an optical vortex for any application, it is important to know if the vortex is axial or non-axial, since properties of one type of the vortex are quite different from another. We show that the Wigner distribution can provide a solution, being different for axial and non-axial vortex. We use transport properties of the Wigner function to study the propagation of an axial as well as non-axial vortex and find them different.