Research On Generation And Tiansmission Characteristics Of Vortex Beam

The vortex beam is a kind of special beam with a helical phase wavefront structure and certain orbital angular momentum.In recent years,the vortex beam has been widely used in particle manipulation,photon calculation,biomedicine,and optical space communication.The high-order Bessel-Gaussian beams is a type of vortex beam,which not only has the special properties of a vortex beam,but also is a non-diffracting beam within a certain distance.It has special advantage in the field of microscopic particle manipulation and other fields as well.In this thesis,the simulation of the transmission characteristics of vortex beams is studied.Firstly,the long-distance transmission of the vortex beam was simulated,and the SeeLight simulation platform was used to compare the long-distance transmission between the vortex beam generated by the laser incident on the spiral phase plate(SPP)and the Gaussian beam generated by the laser.The transmission conditions were divided into vacuum and turbulence atmosphere.Secondly,the high-order Bessel-Gaussian beams generated by a Gaussian beam via a SPP-Axicon system are analyzed.According to Fresnel diffraction theory,the generation of high-order Bessel-Gaussian beams is deduced.The topological charge numbers measurement method for high-order Bessel-Gaussian beams is given by simulation experiments;the transmission analysis of high-order Bessel-Gaussian beams within the non-diffracting distance is emphasized.The analysis mainly includes different distances,different topological charge numbers and different axicon angles,which has a certain guiding significance for the generation and application of high-order Bessel-Gaussian beams,and,the energy distribution on the observation surface at certain distance was analyzed.Finally,the transmission characteristics of off-axis high-order Bessel-Gaussian beams are analyzed.Usually,the Gaussian beams emitted from the laser is hardly aligned with the centers of the spiral phase plate and axicon,which is the cause of the off-axis vortex beam's generation.In this thesis,the effects of transmission distance,topological charge numbers,and off-axis parameters on the off-axis high-order Bessel-Gaussian beams are analyzed.Because the non-alignment of beams and optics in the experiment is unavoidable,the study of off-axis vortex beams has an important practical significance.