Tight Focusing Characteristics And Optical Capture Applications Of Rotationally Symmetric Power Exponential Phase Vortex Beam

The rotationally symmetric power exponential phase vortex beam is a new type of beam with power exponential phase wavefront.The light intensity is petal shaped,and the number of petals is equal to the topological charge.Compared with vortex beams,the phase distribution of rotationally symmetric power exponent phase vortex beams is related to the topological charge and power exponent,which determine the number of lobes and the phase gradient distribution,respectively.Rotating symmetric exponential phase vortex beams have special advantages in optical capture applications,but there are currently few reports on optical capture research based on rotating symmetric exponential phase vortex beams.Therefore,this article investigates the tight focusing characteristics and optical capture applications of rotationally symmetric power-exponential phase vortex beams.The main research contents are as follows:（1）We studied the propagation and tight focusing characteristics of rotational symmetric power-exponential phase vortex beams.Based on the Collins formula and Richards-Wolf theory,an optical transmission and tight focusing model for rotationally symmetric power-exponential phase vortex beams was established.The paraxial transmission and tight focusing characteristics in free space were studied through numerical calculations and experimentally verified.It is shown that the radial order of the Laguerre Gaussian rotationally symmetric power exponent phase vortex beam is equal to the number of the outer circles of the beam,the beam intensity distribution is an isolated lobe and the number of lobes is equal to the topological charge of the beam,the beam power index is proportional to the concentration degree of the beam energy,and the beam intensity size is proportional to the topological charge and the radial order.The research results provide a theoretical basis for the application of rotational symmetric power-exponential phase vortex beams in optical capture.（2）We studied the optical trapping force of rotational symmetric power exponential phase vortex beams.Based on the theory of gradient force and scattering force of light pressure,a photodynamic model of optical trap force capturing microspheres was established.On the basis of studying the electromagnetic model of microsphere size and optical trap force,a optical trap force model of rotating symmetric power-law phase vortex beams was established based on the T-matrix method and extended boundary conditions;By numerical simulation,the capture efficiency of optical traps in the vertical/parallel beam propagation direction plane is studied,and the effects of beam power,numerical aperture,topological charge,and microsphere refractive index on the capture efficiency are analyzed.The research results indicate that the gradient force and scattering force form a stable optical trap for capturing microspheres at the equilibrium point.By adjusting the beam power,numerical aperture,and topological charge of the input light,the capture efficiency of the optical trap can be improved.The research results lay a theoretical foundation for the capture of multiple microspheres by rotating symmetric exponential phase vortex beams.（3）We studied the optical capture application of rotational symmetric power-exponential phase vortex beams.Based on the theory and application of optical trapping force capture,an optical tweezers experimental system based on rotational symmetric power-exponential phase vortex beams was designed and constructed.The experiment studied the three-dimensional optical trapping of Si O₂ microspheres formed by rotational symmetric power-exponential phase vortex beams after tight focusing,achieving multi microsphere capture.At the same time,the effects of radial polarization state,optical power,and microsphere size on optical trapping experiments were studied.The research results indicate that rotating symmetric power-exponential phase vortex beams can not only achieve multi microsphere capture,but also capture Si O₂ microspheres with the same number of topological charges.By adjusting the polarization state and power of the input light,the optical capture ability can be improved.The research results provide new ideas for the optical capture application of rotationally symmetric power-exponential phase vortex beams,and are of great significance for promoting the generation and application research of rotationally symmetric power-exponential phase vortex beams.