Estimating topological charge of propagating vortex from single-shot non-imaged speckle

Abstract

Encoding information using the topological charge of vortex beams has been proposed for optical communications. The conservation of the topological charge on propagation and the detection of the topological charge by a receiver are significant in these applications and have been well established in free-space. However, when vortex beams enter a diffuser, the wavefront is distorted, leading to a challenge in the conservation and detection of the topological charge. Here, we present a technique to measure the value of the topological charge of a vortex beam obscured in the randomly scattered light. The results of the numerical simulations and experiments are presented and are in good agreement. In particular, only a single-shot measurement is required to detect the topological charge of vortex beams, indicating that the method is applicable to a dynamic diffuser.

Vortex beam generation by fabricating spiral phase plate on fiber tips

“…These unique features render vortex beams in great demand for a variety of scientific, medical, and communication applications, such as optical measurement, [2], [3] photon manipulation, [4], [5] super-resolution imaging, [6] and quantum information communication. [7], [8] At present, various methods have been developed for vortex beam generation, such as mode conversion, [9], [10] digital holography, [11] spatial light modulation, [12] microscopic ring resonators, [13] active vortex laser generators, [14], [15] as well as spiral phase plates (SPP). [16]- [18] The SPP can directly generate high conversion efficiency and high power vortex beam by adjusting the thickness or refractive index, and it is usually fabricated by an optically transparent medium with high optical transmittance.…”

High-accuracy mode recognition method in orbital angular momentum optical communication system

“…In 1992, Allen et al indicated that for beams with helical phase fronts of expilϕ the OAM in the propagation direction has the discrete values of lh per photon, where h is the reduced Planck constant, and l is usually an integer that represents the topological charge (TC), whose sign indicates the direction of the phase spiral [2] . In theory, the VBs with different OAM modes are mutually orthogonal, and their intensity distribution presents unique "doughnut" shapes due to phase uncertainty at the beam cross section [3] . The discovery of optical vortices carrying OAM has accelerated progress in many research areas [4] .…”

Rapid fabrication of microrings with complex cross section using annular vortex beams

“…Until now, some very specific distributions, including Bessel beams [4] , spatially shifted vortex beams [5] , double-helix beams [6] , and ring-shaped beams [7] , have been explored for parallelization of the direct laser writing or even single-shot microfabrication. Among these methods, Bessel beams [8] and vortex beams [9,10] have been widely applied to generate ring-shaped foci. With the flexible control of parameters of Bessel and vortex beams, the diameter of ring-shaped focus can be easily adjusted.…”