Focal field properties of toroidal double-mode vector beams

Integer-order vector beams maintain their polarization properties under the paraxial diffraction condition. Fractional-order vector beam with irregular phase change that leading to changeable focusing properties has aroused huge interest research. Herein, we proposed and experimentally generated a double-mode concentric annular fractional vector beam. Based on the modal superposition, the intensity and spin angular momentum (SAM) density are characterized by periodic changes from rotational symmetry to axial symmetry as the topological coefficient increases. These results reveal that the fractional topological coefficients have a great potential degree of freedom. The experimental results are exploited in this work to emphasize the important connection between fractional coefficient and SAM density.

Automated summary

This paper introduces a double-mode concentric annular fractional vector beam, and the results show that fractional topological coefficients have a high degree of freedom, emphasizing the important connection between fractional coefficients and SAM density through experimental results.