Study On The Generation Of Three-dimensional Optical Vortex Traps

Vortex beam is a kind of special beam with helical wave-front.Vortex beams have many potential applications in optical manipulation such as trapping and rotating colloid particles or even living cells,on account of its phase singularity and the internal orbital angular momentum.The many novel characteristics of vortex beams have created a wave of research and has been applied to various fields such as optical communication,quantum information coding,micro-measurement,biomedicine,and micro-imaging.Compared with the limitation of conventional optical tweezer,traps with vortex beams allow the trapping of absorbing and high-index particles with less risk of damage and better isolation.This article research on the application of vortex light in the field of optical tweezers base on the study of the characteristics of vortex beam.Combining the vortex beam with optical tweezers,we propose a technique of generating a multi-vortex beam array from a single phase hologram on the strength of computational holography using a spatial light modulator(SLM).By modulating the phase hologram on the SLM,it is possible to arbitrarily steer the exit vortex beams in the well-setting position and focus in different planes along vertical coordinate to form a potential spatial structure of traps to trap and manipulate particles.What's more,the flexibility of the modulator allows the spatial configurations of the traps well to be dynamically transformed,increasing the freedom and flexibility of vortex manipulation.The corresponding efficient and flexible system has the ability to promote the service efficiency and application range of the optical tweezers.The major contents of this paper consists of follows parts:Firstly,the present research situation of optical vortex and optical tweezers is introduced here,and then analyze the principle of the optical tweezer on the strength of geometric model and electromagnetic field model,as well as its implementation in optical manipulation and its application in biology,cytology and other fields.Subsequently,detailed illustration the basic principle and related characteristics of the vortex beam from the point view of electromagnetic field and Poynting vector.Enumerate several common vortex beams and applications,as well as the advantages and disadvantages of several vortex generation methods.Combining vortex beams and optical tweezers,demonstrate the theoretical basis of the particle manipulation base on using vortex beams and how the LCOS-SLM modulated vortex beams.On account of compute-generated hologram projecting on LCOS-SLM,we designed a scheme to arbitrarily modulate the exit angle and focus plane of the vortex beams array.Finally,according to the design scheme proposed in this paper,simulation and experiment are conducted,and the experimental results are analyzed.The experimental results are basically consistent with the theory,and the arbitrary two-dimensional structure distribution of vortex light is achieved.At last,this paper summarizes the problems and put forward improvements in this work,moreover looks forward to the innovation using in super-resolution optical microscopy.