Fabrication And Measurement Of Perfect Optical Vortex Phase Plates Based On Laser Direct Writing

The optical vortex is a kind of beam carrying orbital angular momentum.Its phase front is helical and the distribution is ring-shaped.These special properties make the vortex beam widely applied in the fields of micro-particle manipulation,optical information transmission,and laser shaping,especially the perfect optical vortex whose radius is independent of the topological charge.In recent years,research on perfect optical vortex is no longer limited to beams with circularly symmetric distribution.More and more perfect vortex beams with different modes have been proposed,which is of great significance for information transmission and beam shaping.In this paper,based on femtosecond laser direct writing technology,phase plates used to generate perfect vortex beams with different modes are designed and fabricated,and their optical characteristics are tested and analyzed.The main research includes the following aspects:(1)Based on femtosecond laser direct writing technology,two kinds of perfect optical vortex phase plates were designed and fabricated,and the influence of the optimal processing parameters on the surface profile was studied.The results from the experimental measurements show that the phase plates have good optical properties.(2)A phase plate for generating elliptic perfect optical vortices is proposed.It is designed by superimposing the optimal phase element and the Gabor zone plate.The size of the generated beam can be adjusted by changing the scaling factor of the phase plate,and the ellipticity can be adjusted by changing the ellipticity factors.The phase plates prepared by the femtosecond laser direct writing system have smooth and continuous surface profile.Numerical simulations and experimental results prove that the proposed phase plate can realize the control of the topological charges,size and eccentricity of elliptic perfect optical vortices.