Research On The Propagation Of Cylindrical Vector Beam And Radiation Force Properties

Polarization is an important property of light.The vector characteristics of light and its interaction with matter can generate kinds of peculiar optical properties.In recent years,cylindrical vector(CV)beams have gained considerable attention due to their peculiar polarization and focusing properties and useful applications such as high-resolution imaging,optical storage,nanolithography,optical trapping,particle acceleration.Therefore,it is of great practical significance to explore and regulate the tightly focusing performances of the CV beams.Based on the Richards-Wolf vector diffraction theory,we study systematically,respectively,the tightly focusing properties of CV beams and the optical force of particle in the focused optical field by combining helical phase for wavefront modulation of a beam.The main research contents are as follows:1.Based on the Richards and Wolf vector diffraction theory,the analytical model for calculating the electromagnetic fields and Poynting vectors of the tightly focused CV beams was built.The effects of the polarization indices,initial polarization phase and topological charge of spiral phase on the distribution of tightly focused field was discussed.2.The transverse energy flow ring with rotational symmetry in the focal plane was obtained through adding a traditional spiral phase to tightly focused radially and azimuthally polarized beam.Further,the redistribution of the transverse energy flow of the tightly focused radial and azimuthal polarized light by designing annular vortex phase masks are explored.This special effect enables absorptive particles to be transported along a more flexible path.3.The effect of the light field of the tightly focused CV beam on the light radiation force of particles was studied.The spin angular momentum,the optical force on the particle and the optical moment in the tightly focused CV field were calculated.The results show that the direction and magnitude of the spin angular momentum,as well as the optical force and spin torque on the particle,can be controlled by adjusting the polarization state of the input beam.Finally,We note that the spin torque in magnitude can be controlled further by changing the properties of the particles.4.It is proved theoretically that the optical trapping with adjustable trapping range is possible in theory.A focus with controllable length and subwavelength width in the 4? focusing system has been constructed.Through a detailed force-field analysis,it is found that gold nanoparticles can be trapped in three dimensions.In addition,the trapping range can be easily adjusted by changing the parameters as needed.