Focus tunable vector autofocusing Airy vortex beams resist atmospheric turbulence

Abstract

The rapid increase in orbital angular momentum (OAM) mode size with increasing modal order, given the limited-size of the receiver, is a major impediment to high-capacity OAM mode multiplexing in practice. Based on the Pancharatnam-Berry (PB) phase theory, we correlate the change of the polarization state with the curvature of the wavefront isophase line in the source plane and manipulate the focusing ability of vector autofocusing Airy vortex beam (AAVB) by combining the isophase line curvature and the intensity gradient of the beam, which are two independent degrees of freedom. The present method enables flexible on-demand focusing of vector AAVBs in free space and is more effective in focusing higher order OAM modes, which can reduce the full-width at half maximum (FWHM) of the AAVB with topological charge l= 25 to 1/5 of that of the conventional scalar type. And the modulated vector AAVB is superior to the conventional scalar one in terms of mitigating atmospheric turbulent disturbance. The work provides a potentially useful basis for improving the capability of future free-space OAM systems for large-scale dense communications.