Polarization and orbital angular momentum properties of focal field partially coherent beams with double vortexes

Abstract

The light intensity, polarization degree and orbital angular momentum density of partially coherent radially polarized beams carrying double vortexes after being focused by a high numerical aperture lens are obtained based on Richards– Wolf vectorial integral theory. The tight focusing properties of the beam including polarization degree and orbital angular momentum density are discussed. The influence of the source coherence length of the incident beam and the numerical aperture of the lens on the focusing characteristics is studied. Results show that the distribution of polarization degree and orbital angular momentum density presents a petal-like pattern, and the number of petals is related to the topological charge. The changes in the source coherence length and the numerical aperture affect the focusing properties of the beam. More useful orbital angular momentum is obtained after vortex beams are focused through a high numerical aperture lens. These results may provide a theoretical reference for the tight focus of vortex beams and the application of polarization and orbital angular momentum.