Three-dimensional Focal Field And Photophysical Properties Of Fractional Vortex/vector Beams

With the continuous developing of optical technology research,light as a carrier of information and energy has a wide range of applications in the fields of particle manipulation,optical sense detection and optical information.In order to take advantages of multi-parameter combining to control of physical properties such as beam amplitude,phase and polarization,spatial modulation of light is essential.The most important influence on the interaction between light and matter such as particle manipulation and light-induced rotation is the basic property parameters of light,such as phase and polarization.In the process of particle manipulation and capture,the energy flow of the input beam focal field is transmitted to particles and guides the movement of the particles.The beam which has the spin and orbital angular momentum will also be transferred to the particles,generating rotational torque.Compared with the integer-order vortex/vector beam,the fractional vortex/vector beam has the unique phase and polarization distribution,so it will produce novel tight focus fields and photophysical properties,providing new control methods for the manipulation and capture of particles.We are looking forward to discovering new phenomena.Focusing on the application requirements of particle manipulation,this paper studies the focal field theory of the fractional vortex/vector beam under the conditions of tight focusing,and explores the influence and control characteristics of the focal field distribution of the fractional topological charge.By researching the angular momentum,especially the transverse spin angular momentum and the study of energy flow characteristics,analyze the new phenomenon and new mechanism of the Spin-Orbit interaction of light and the transverse spin angular momentum.The research results provide theoretical guidance for complex optical switches,asymmetric particle capture and manipulation requirements.The main research contents are as follows:First,based on the Richards-Wolf vector diffraction theory,an analytical expression for tightly focused fractional vortex/vector beams is derived,which clarifies the equivalent superposition integer vortex/vector light is the fractional vortex/vector light.The generation of two types of beams and focal field detection methods are studied,and some experimental results are given.Secondly,the three-dimensional focal field intensity,transverse spin density,and the coupling characteristics of spin and orbital angular momentum of fractional vortex uniformly polarized beams are studied,the influence of phase topological charge and uniform polarization state in focus field and corresponding photophysical parameters are found,the phenomenon of the spatial separation and coupling of spin and orbit under the conditions of tight focus is analyzed.Finally,the three-dimensional focal field,angular momentum,linear momentum and torque characteristics of the fractional vector optical tight focus are studied.Flexible control the three-dimensional focal field distribution and spin axis orientation of fractional vector light,through selecting the fractional polarization topological charge.Based on the mode superposition of different integer order vector beams,the spatial separation of the three-dimensional focal field of fractional vector light and the lateral separation of the distribution of spin angular momentum/orbital angular momentum have been discovered.The energy flow distribution under integer and fractional topological are compared and studied,which provides flexible manipulation possibilities for the capture and transmission of multiple particles,and the flexible transportation of the controllable path of absorptive particles.