Partially Coherent Off-Axis Double Vortex Beam and Its Properties in Oceanic Turbulence

Abstract

A partially coherent off-axis double vortex beam (PCOADVB) composed of two off-axis vortices is theoretically presented. The analytical equations of a PCOADVB in oceanic turbulence are presented, and the intensity profiles and the number of coherence vortices of the PCOADVBs are investigated based on the derived expressions. The numerical results show that the intensity profiles of PCOADVBs are determined by the initial topological charges M1 and M2 and the positions of the off-axis vortices (x1d,y1d) and (x2d,y2d). The intensity profiles of PCOADVBs will lose the off-axis ring intensity profile and acquire a Gaussian-like profile as z increases, and stronger oceanic turbulence and a smaller σ can help the PCOADVB evolve into a spot with a Gaussian-like profile faster on propagation. The number of coherence vortices of a PCOADVB in oceanic turbulence will increase on propagation. The PCOADVB may have potential applications in underwater laser sensing and wireless communications.

Transmission characteristics of partially coherent pin-like optical vortex beams in oceanic turbulence

“…Underwater wireless optical communication (UWOC), which has the advantages of large bandwidth, high transmission rate and good confidentiality, has attracted the attention of a wide range of researchers [1,2]. Vortex beams, characterized by their possession of orbital angular momentum (OAM), with each photon carrying an OAM value of m 0 ÿ, where unlimited index m 0 represents the topological charge and ÿ is reduced Planck constant, can provide another degree of freedom for multiplexing applications due to the orthogonality among different OAM indexes [3][4][5][6][7][8]. It has been shown that the OAM multiplexing technique can significantly enhance the transmission efficiency of UWOC systems [9][10][11][12][13].…”