Study On Controlled Modulation And Transmission Dynamics Of Complex Vortex Beam

As a kind of singular beam with a special helical wavefront,the vortex beam has attracted the attention of researchers since its discovery.The orbital angular momentum carried by a vortex beam makes it widely used in complex particle control,free space optical communication,optical imaging,and other fields.With the complexity of the application environment,the common vortex beam cannot meet the demand because of its fixed light intensity distribution and single mode orbital angular momentum.Therefore,it is very important to adjust and control the relevant characteristics of the vortex beam,expand the modulation characteristics of the vortex beam and improve its utilization.This paper is mainly based on the modulation processing of vortex beams such as phase modulation,spatial diffraction,etc.,to achieve the modulation of the relevant characteristics of complex vortex beams(such as open-loop facula,phase gradient,beam shaping,and high-order orbital angular momentum)and transmission research.The main work of this paper is as follows:1.Based on the power exponential phase and spiral phase,the Bessel Gaussian beam with non-uniform phase gradient distribution is reconstructed,and the transmission in space and the light intensity distribution in the far field are calculated and analyzed by Fraunhofer diffraction integral algorithm using MATLAB software,and the open-loop control of the Bessel Gaussian beam in the far field is realized by controlling the phase gradient distribution.In addition,the phase-blocking transfer function is set to simulate and analyze the intensity distribution of the beam in the blocked state.The numerical simulation and experimental results show that by adjusting the parameters of the power exponential phase and the phase barrier angle,the reconstructed Bessel Gaussian beams can generate different sizes and directions of the openings in the far field,to realize the open-loop control of the beams,which makes the open-loop beams have a wide range of application scenarios in particle capture and guidance.2.A perfect vortex beam with a double-ring intensity distribution is produced by Fourier transforming the Bessel beam embedded in the phase of the axial cone.The spacing of the two bright rings in the beam can be changed by adjusting the axis cone phase parameter and the beam stretching factor,and the relationship between the ring spacing and the modulating parameters is analyzed.In order to characterize the double-ring perfect vortex beam,interferometric experiments are performed to demonstrate that the size of the bright rings is independent of the topological charge and that both rings have the same topological charge.Therefore,the beam has more orbital angular momentum than the traditional perfect optical vortex.The adjustable ring spacing makes the superposition state of the double ring beam produce different light intensity distributions.In addition,the generation of double ring vortex arrays and the shaping of double ring beams fully demonstrate the multi-dimensional adjustable characteristics and multiple degrees of freedom of selection of double ring perfect vortex beams.3.The high-order phased vortex array with arbitrary curve arrangement distribution is generated based on the phased Gaussian array and the high-order processing(phase multiplication).The distribution mode of orbital angular momentum under its high-order is analyzed through spiral spectrum expansion,and the number of phase singularities under its high-order is also detected through interference experiments.The increased orbital angular momentum mode and number of singularities under its high-order verify the feasibility of generating high-order vortex array.In addition,depending on the discrete phase characteristics of the phased Gaussian array,the polygonal phased vortex array with different phase gradients is generated by splicing the phased Gaussian arrays with different phase differences,which realizes the multi-dimensional control of the orbital angular momentum and phase gradient of the phased vortex array.In this paper,the modulation of intensity distribution,phase gradient,orbital angular momentum,and other related characteristics of vortex beams is achieved by adjusting phase structure,which breaks the characteristics of traditional vortex beams with annular distribution and single orbital angular momentum mode and provides additional freedom of choice including phase gradient,phase barrier Angle,ring spacing,spot shape and so on.In conclusion,this work provides important support for the application of vortex optical fields in complex particle manipulation,free space optical communication,and microscopic imaging.