Research On Propagation Characteristics And Deep Focusing Of Perfect Optical Vortex Beams

Vortex light carries orbital angular momentum,which provides a wide range of applications in the fields of quantum information coding,particle trapping and manipulation.Relevant studies also show that information coding using orbital angular momentum has higher confidentiality.Therefore,it is important to measure the topological charge of the vortex beam.A variety of methods for measuring the topological charge of a vortex beam have been proposed,and the use of pupil diffraction is relatively simple and feasible.In fact,the deep focusing of a beam means that the beam is focused through a high numerical aperture lens.Compared with ordinary focusing,it can produce a sub-wavelength spot.This special property can effectively improve the spatial resolution of the focusing imaging system,overcome the traditional diffraction limit,and has great research significance in the field of optics.The electric field distribution of the perfect vortex beam is described and its characteristics are introduced.In the traditional vortex beam,the topological charge is proportional to the bright ring radius and the orbital angular momentum(OAM),which determines the wavelength division multiplexing and information coding ability.It is an important parameter in the research.The advantages of perfect optical vortex beam(POV)are controllable loop width,radius and topological charge,and high lateral and axial strength gradients.POV has important application value in the fields of Bose-Einstein condensation,particle rotation and manipulation,optical super-resolution imaging and quantum information coding.POV has become a very important frontier research hotspot in the field of information optics in recent years.However,the transmission and deep focusing characteristics of POV need to be studied.The contents of this paper are as follows:1.The theoretical analysis of the perfect vortex beam through the rectangular and rectangular ring pupil far-field diffraction.By changing the relevant parameters of each pupil and the topological charge of the incident beam,the transmission characteristics of the beam passing through the rectangular and rectangular loops are simulated.The far field diffraction patterns of different pupils are analyzed to obtain the correspondencebetween the regular pattern and the topological charge.Without extracting the phase,the measured topological load can be directly obtained.2.According to the cross-shaped aperture,double-cross and cross-array apertures are proposed.The far-field diffraction properties of the perfect optical vortex beam through the cross and multi-cross-shaped grating are studied.By changing the parameters of each diaphragm and the topological charge of the incident beam,the propagation characteristics of the beam through different cross-shaped diaphragms are simulated and analyzed.The far-field diffraction patterns of different diaphragms are analyzed.According to the diffraction patterns,a new method to detect the topological charge is obtained.3.The formula derivation of the perfect optical vortex beam deeply defocused by high numerical aperture lens.The simulation analysis of the perfect optical vortex beam based on the intensity distribution and phase characteristics of the deep focus after the Richards-Wolf diffraction theory is studied and compared with the change of the focusing characteristics under different numerical apertures.The intensity distribution and phase characteristics of the components of the deep focus field on the x-axis,y-axis and z-axis are compared and analyzed.The application prospect of the perfect vortex beam light field in particle capture after deep focusing is analyzed.