Two-dimensional Talbot effect of the optical vortices and their spatial evolution

Denis A Ikonnikov,Mikhail N Volochaev,Vasily G Arkhipkin,Sergey A Myslivets,Andrey M Vyunishev

doi:10.1038/s41598-020-77418-y

Denis A Ikonnikov, Mikhail N Volochaev + Show 3 more

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https://doi.org/10.1038/s41598-020-77418-y

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Journal: Scientific Reports	Publication Date: Nov 20, 2020
Citations: 25	License type: open-access

Affiliation: Institute of Physics

Abstract

We report on the experimental and theoretical study of the near-field diffraction of optical vortices (OVs) at a two-dimensional diffraction grating. The Talbot effect for the optical vortices in the visible range is experimentally observed and the respective Talbot carpets for the optical vortices are experimentally obtained for the first time. It is shown that the spatial configuration of the light field behind the grating represents a complex three-dimensional lattice of beamlet-like optical vortices. A unit cell of the OV lattice is reconstructed using the experimental data and the spatial evolution of the beamlet intensity and phase singularities of the optical vortices is demonstrated. In addition, the self-healing effect for the optical vortices, which consists in flattening of the central dip in the annular intensity distribution, i.e., restoring the image of the object plane predicted earlier is observed. The calculated results agree well with the experimental ones. The results obtained can be used to create and optimize the 3D OV lattices for a wide range of application areas.

Highlights

We report on the experimental and theoretical study of the near-field diffraction of optical vortices (OVs) at a two-dimensional diffraction grating
The Talbot effect for the optical vortices in the visible range was experimentally observed and the corresponding Talbot carpets for the optical vortices were observed for the first time
It was numerically shown that the phase distributions within the unit cells of a specific image at the integer Talbot planes causes a complex structure of the bounded phase singularities of the opposite signs, i.e., the vortices and anti-vortices, so the resulting topological charge (TC) is zero

Summary

Introduction

We report on the experimental and theoretical study of the near-field diffraction of optical vortices (OVs) at a two-dimensional diffraction grating. It should be noted that the diffraction of the OAM-carrying beams was studied for the cases of a single s lit[28,29], sector-shaped d iaphragm[30], and 1D gratings[31] It is well-known that a plane wave incident onto a periodic grating is diffracted such that the Talbot effect occurs in the near-field[32]. The physics behind this phenomenon is interference of diffracted waves, which results in the intensity distribution (image) self-reproduction at distances multiple of Talbot length ZT = 2 2/ , where is the grating period, is the wavelength of the incident wave This phenomenon is well-studied, both theoretically and experimentally, for plane w aves[33] and theoretically investigated for the beams comprising phase singularities[20,34,35]. According to5, the TC of the optical vortex can be found using the path integral over the closed curve C subtended by a phase surface (over the field cross section) containing the singularities

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