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 [1, 2]. 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 [3]. 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.

Production of orbital angular momentum states of optical vortex beams using a vortex half-wave retarder with double-pass configuration

“…Nevertheless, to identify the OAMs with diffraction patterns, the propagation of has to be involved 5 . According to our previous report 31 , we have applied adjustable combination gratings ( and in Fig. 1 ) for generating the near-field Talbot effect to determine both order and charge of the OAMs.…”

“…Both are normal binary gratings (200 m period, chromium on glass, Edmund Optics Inc.). A translation stage (TS, MTS50/M-Z8, Thorlabs) can be adjusted for an arbitrary effective open fraction 31 , 49 of the Talbot patterns by moving the second grating ( ) transversely in order to obtain sharp Talbot images for detection by a USB 2.0 CMOS camera (Camera, DCC1545M, Thorlabs). The distance between the first ( ) and second ( ) grating was set to one Talbot distance ( ), as was the distance between the second grating and the camera.…”

“…On the other hand, the extra-cavity conversion mean is related to generation of an optical vortex outside the laser cavity using optical elements such as a SLM 26 , 27 , a forked grating 28 , cylindrical lenses 29 , and transmissive programmable metasurfaces 30 . Recently, polarization optics configuration known as a vortex half-wave retarder (VHWR) has been utilized to convert Gaussian laser beams into Laguerre-Gaussian modes with OAM 20 , 31 . Xiujian Li et al illustrated that high-order cylindrical vector beams were realized by cascading multiple VHWRs 32 .…”

“…Two-dimensional Talbot effect of the optical vortices has also been reported 48 . It was demonstrated later that the Talbot patterns resulting from an overlapping grating configuration can provide high optical vortex detection efficiency 31 , 49 . Not only has the Talbot effect been shown to help determine the OAM of light, but it also has other potential applications 50 – 53 .…”

“…In this paper, a new economical double-pass configuration through VHWRs is proposed for the creation of optical vortices of several OAM orders. These OAM beams are detected and distinguished using the high-contrast Talbot patterns formed via the overlapping grating setup 31 , 49 . The influence of the vortex polarization states of light on the Talbot effect was also investigated.…”