Trapping Force Acted On A Particle With A Dual-vortex Optical Trap

Optical vortices is the optical potential basing on the interaction between the scattering force and the gradient force,and can control micro-particles ranging in size from tens of nanometers to tens of micrometers.As the Optical vortices has the characteristics of non-contact and no invasion,and becomes the important implement of the biology science and promotes the interaction and the development between the physics and biology.Recently,generation and characterization of beams interfered by double vortex beams have intensively been implemente,and interferences by two vortex beams with charges of l1=-l2 have also been employed for stably trapping microparticles without rotation as the OAM in each interfering beam have been cancelled out after the coherent superposition. In this paper,We calculate both longitudinal and transverse forces acting on a spherical absorbing particle in air with a dual-vortex optical trap.The relationship between the radius of the particle by dual-vortex optical trap and longitudinal forces was calculated theoretically.We analyze the condition of the beam waist and the diffraction length with the longitudinal force.The relationship between of the ring radius of the beam and transverse forces was numerically calculated.Through the analysis,we obtain the maximum transverse forces when the ratio of the radius of the particle and the ring radius of the beam is constant.The whole paper is divided into five chaptersChapter 1:The history and the main developments of the optical vortices are reviewed,and the main applications are also summarized.In additionthe,main contents of the thesis and our research results in the field are given.Chapter 2:The fundamental theory of optical vortices is introduced.Firstly optical vortices is defined and describted in mathematics specifically.Experiments of measuring the orbital angular momentum of light and indicating the transfer of orbital and spin angular momentum from light to matter in different conditions are introduced.Chapter 3:The third chapter presents the force analysis in Gaussian beams.The fourth chapter analyse a particle in the vortex optical field.The fifth chapter study the angular momentum of optical vortices and research progress of optical vortex.Chapter 4:We calculate both longitudinal and transverse forces acting on a spherical absorbing particle in air with a dual-vortex optical trap. The relationship between the radius of the particle by dual-vortex optical trap and longitudinal forces was calculated theoretically.