Probing vortex beams based on Talbot effect with two overlapping gratings

Abstract

In a prior report the optical vortex was characterized using the near-field Talbot effect (Panthong et al 2016 J. Opt. 18 035602; Panthonget al 2018 Appl. Opt. 57 1657). This near-field technique can resolve both order and charge of the orbital angular momentum state of the vortex beam. We have proposed before that a small open fraction of the grating in the Talbot configuration can improve the image contrast (Srisuphaphon et al 2020 J. Opt. Soc. Am. B 37 2021). In this study, we combine these previously reported techniques, i.e. the Talbot effect for probing an optical vortex and overlapping gratings to manipulate the open fraction. Both theoretical simulation and experimental demonstration are presented here. We believe that our technique can be an alternative method for optical vortex imaging, and could be useful in optical applications.