Propagation of an optical vortex beam through a diamond-shaped aperture

The propagation of an optical vortex beam through a diamond-shaped aperture is studied both numerically and experimentally. It is found that the diffraction pattern of the vortex beam through the diamond-shaped aperture is related with the topological charge m of the incident optical vortex beam. Thus, the magnitude of the vortex can be measured by using this method. A higher-order optical vortex (|m|>1) is topologically unstable and splits into |m| vortices with unit charge in the diffraction field, which deviate from the optical axis with a distance. The distance increases upon propagation. The theoretical predictions are confirmed by our experiments.

► The propagation of a vortex beam through a diamond-shaped aperture is studied both numerically and experimentally.
► The diffraction pattern is related with the topological charge m of the incident beam.
► The magnitude of the vortex can be measured by using this method.
► A higher-order vortex is topologically unstable and splits into |m| vortices with unit charge.
► The theoretical predictions are confirmed by our experiments.