Mitigating Vortex Splitting by Controlling the Wavefront Isophase Line Curvature of Vector Autofocusing Airy Vortex Beams in Free Space

Abstract

The match between the orbital angular momentum (OAM) transmission and receipt is a prerequisite for vortex beams as a carrier of the wireless optical communication system in free space. However, the vortex splitting induced by atmospheric turbulence results in an offset in the average OAM measured after propagating over the free space optical communication link. Therefore, how to reduce the vortex splitting effect to improve the stability of orbital angular momentum propagation is studied in this paper. First, a new parameter (m) is introduced to modulate the radial distribution of the polarization state of the autofocusing Airy vortex beams (AAVBs). Second, to control the optical field distribution in focal plane, the wavefront isophase line curvature of the AAVBs is reconstructed by using the Pancharatnam-Berry phase generated in the polarization conversion process. Finally, by comparing the vortex splitting rates of the AAVBs with different wavefrontisophase line curvatures under different turbulence environments, it can be found that the vortex splitting in free space can be effectively mitigated by choosing an appropriate wavefront isophase line curvature. In addition, the mitigation effect is more obvious in the atmosphere with stronger turbulence. This study provides a new feasible method to control the phase structure of vortex beams and promises potential applications in the OAM-based free space optical communication system.