Focusing Field Modulation And Application Based On The Perfect Optical Vortices

Vortex beam is one of the research hotspots in the field of optics because it carries orbital angular momentum and the intensity distribution of focus is hollow ring shaped.The intensity distribution of vortex beams will change with the different value of topological charges,and the perfect vortex beam is a special form whose intensity distribution of ring is not affected by its topological charge.Compared with traditional vortex beams,it can greatly improve the application efficiency of optical micro-manipulation,micro direct laser writing,optical communication and optical storage.The perfect vortex beam is an idealized theoretical model,and it is difficult to produce in the experiment.When the topological charge is greater than a certain threshold value,it will cause obvious distortion of the ring intensity of the perfect vortex beam.At the same time,due to the system deviation or the defects of the experimental setup,the focusing precision of the perfect vortex beam will be affected to different degrees in the tight focusing system.Therefore,it has important research significance and application value in the field of optics to improve the regulation precision of perfect vortex beam and expand its application,and to study the regulation methods of different focusing light fields of perfect vortex beam.The main research contents of this paper are as follows:1.From the Richards-Wolf vector diffraction theory,the corresponding relationship between the intensity distribution of the compact focusing field and the phase of the incident light is studied and analyzed,and the pure phase expression formula related to the single focus position in the compact focusing system is derived.Based on this phase expression,phase holograms can be directly encoded by adjusting the position coordinates of a single focus in the compact focusing field.By modulating the phase hologram loaded into the spatial light modulator,the three-dimensional spatial position of the focusing spot can be controlled freely.2.Based on the theoretically derived pure phase distribution expression related to the focusing position,a method to generate perfect vortex beams by superimposing multiple single-focus pure phase expressions is proposed,and its focusing performance under tight focusing system is verified.At the same time,to solve the complex amplitude encoding problem of superimposed multiple focal points to produce perfect optical vortices,a two-dimensional grating phase-only encoding method based on sector partition is proposed to better match the phase map of superimposed complex amplitudes.It is proved that the perfect optical vortex generated by the complex amplitude superposition method has no optical intensity deviation in the axial direction,and has stronger anti-distortion ability in the face of higher topological load.3.Based on the perfect optical vortices produced by complex amplitudes superposition,a method of coaxial superposition of perfect optical vortices to generate fringe array optical field and multi-focus is proposed.It is verified that the superposition performance of Bessel-Gaussian beam and vortex beam is much better than that of Bessel-Gaussian beam,and the independent regulation expression for the total number of fringes and topological charge is given.In addition,the flexibility of the complex amplitude superposition method allows the creation of any number and geometric shapes of optical orbits with arbitrary phase gradient distribution density in the focal plane.Furthermore,single-ring perfect vortex beams with heterogeneous topological charges,concentric double-ring perfect vortex beams with different topological charges,and linear orbit beams with phase gradient distribution are created.4.All the proposed optical micromanipulation experiments of structured light fields are carried out.It is verified that the directional transport of particles can be achieved by any orbital optical field with phase gradient distribution.In addition,fringe array light field has been proved to have the ability to capture particle arrays statically for a long time.