Simple technique for producing a 1D periodic intensity profile with a desired open fraction for optical sensor applications

Abstract

The interference contrast in a near-field diffraction pattern can be improved using an asymmetric grating with a small grating window. However, commercial asymmetrically shaped gratings are not available. Here, we report a method that overlaps two gratings to produce an arbitrary open fraction in the combination grating. Both theoretical simulation and experimental observations of the near-field Talbot effect are provided to validate this concept. A characterization of optical vortices is also used as a demonstration of potential applications. This method is simple and can improve the resolution in metrology with optical sensors.

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

“…1 ) gives a reduced effective open fraction . In the near-field regime on assigning both distances and identical to , the self-image of diffracted through grating yields the second self-image with bright fringe width 49 . All of the independent factors and phase constants for the diffraction patterns have been ignored.…”

“…Namely, the left-handed circular polarization (LHCP) produces the vortex with + , while the right-handed circularly polarized (RHCP) light will produce the opposite ( ). The Talbot effect with a diffraction grating ( ) 47 , 55 , together with the use of the grating mask ( ) 49 , made it possible to clearly measure the order and sign of the vortex beam at the same time 26 , 27 . Both are normal binary gratings (200 m period, chromium on glass, Edmund Optics Inc.).…”

“…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.…”

“…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.…”