Partially coherent perfect vortex beam generated by an axicon phase

Vortex beams are structured light fields with a helical phase of the form exp (ilϕ) that carries an optical angular momentum (OAM) of lℏ per photon. Such beams typically have a ring-shaped intensity with a radius that varies with l. Perfect vortex (PV) beams are designed to have a radius that is approximately uniform over a certain OAM range. Here, we report how spatial coherence can be used to maintain a fixed ring shape over a larger propagation distance and for a greater OAM range than is possible for fully coherent vortex beams. Our work is relevant for the application of PV beams in areas such as trapping, tweezing, and optical communications.