Optical Vortex Scanning in an aperture limited system

•We consider an optical system in which an optical vortex is shifted within a Gaussian beam.•We analyze the influence of the aperture diameter on the vortex trajectory.•We present a fast interferometric technique for the phase pattern reconstruction.

We consider an optical system that consists of a vortex lens and a microscopic objective. The system is illuminated with a He–Ne laser. In our previous work we showed that moving the vortex lens perpendicularly to the optical axis makes the optical vortex (introduced by the vortex lens) move inside the focused beam in a characteristic way. We also showed that the vortex trajectory is very sensitive to the position of the observation plane, especially for a large diameter of the incident beam. However, in the microscopic system the aperture is limited by the microscopic objective. In this paper we investigate the propagation of the wide incident laser beam through a vortex lens and then through a microscopic objective with small aperture. We also present a fast interferometric technique for the phase pattern reconstruction of the focused vortex beam.