Mapping optical vortices with a dynamic triangular aperture

Abstract

In this study, we offer a technique that effectively describe the location of vortices. Our method make use of the Fraunhofer diffraction pattern (FDP) produced by a Laguerre-Gaussian beam passing through a dynamic triangular aperture. We found numerically and experimentally that the position of the vortices is associated with the FDPs formed by a triangular aperture. We observed this relationship by mapping the triangular aperture in different positions. A three-point lattice structure of the FDP is seen when the vortex beam interferes with the triangular aperture. On the other hand, at positions away from the beam, there are no distinct structure of the FDPs that can be observed. Hence, the position of vortices can only be determined if a well-known lattice structure of the diffraction pattern is detected. The intensities of the vortex beam passing through various sizes of apertures were also determined and we found that the smallest size of the triangular aperture (r = 0.27) produces the least intense pattern but provides a highest resolution compared to the other two triangular aperture sizes (with r = 0.54 and r = 0.81). We introduce the usage of a digital micromirror device (DMD) which allows us to change the size and position of the apertures at an instant.