Study On The Trapping And Manipulation Of Spherical Particle By Two-fiber Conical Optical Tweezers With Tunable Microcavity

Since the 1980 s,micro-capture and micro-manipulation have been widely concerned by academia.In particular,the study of trapping and manipulating some biological macromolecules,living cells and solid particles has been paid unprecedented attention by scientists in various fields.In this paper,a new type of optical trapping model is proposed to solve the key problem of capturing and collecting solid particles in liquid or gas environment.We study the three-dimensional far field adjustable light capture structure of the spherical double fiber to realize the capture and manipulation of tiny solid microspheres,and then achieve the theoretical and experimental models of captured and collected solid particles,aiming to make breakthrough progress in capture and manipulation of light research in the fiber optics field.The completion of this thesis will not only enhance the competitiveness and influence in the optical capture field of our country,but also has important reference value for application in the environmental governance.Firstly,this paper explored and got more powerful laser tweezers on the basis of the original planar optical fiber optical tweezers-spherical optical tweezers,it is composed by tapered fiber.Compared with the planar optical fiber,the hemispherical surface of spherical optical fiber tip was able to gather the beam strongly,and could form more focused light field in the optical fiber exit area,where there are more photons collided with arrested object to exchange energy and momentum,so as to obtain greater optical trapping force.Then,we introduced double fiber optical tweezers system,aiming to overcome the defects of single fiber optical tweezers that cannot capture the objects of arrest stably and get stronger capture light field and greater force than single fiber optical tweezers.Spherical double fiber optical tweezers system is composed of hemispherical fiber tip made by two exact collimation and spherical optical fiber tip of two-way transmission,ejecting intense laser beams from a hemisphere surface of two cutting-edge form the more focused light field and optical trapping force.Spherical particles were captured and controlled in the double fiber laser beams,the vertical light capture component along the vertical direction of two laser beams of the particles can offset the gravity and achieve suspension completely and to prepare for stable and efficient capture and manipulate the spherical particles.We also introduced the air microcavity,the transmissive laser in the air microcavity can achieve its energy attenuation and change laser convergence effect of spherical optical fiber by changing the length of air microcavity in the front of the tapered fiber,thus changing the effect of the optical trapping force,so we can achieve the purpose that directional move and control at will of arrested object according to our requirements.This kind of the tip spherical fiber is obtained by a moltencone or grinding tip optical fiber in the experiment.Finally,our research group expanded manipulation in liquid to the fog dust particles capture research in the air.After all the study of the calculation of the trapping force,we concluded that the spherical double fiber optical tweezers system can freely capture spherical particles in three-dimensional space,and tunable length air microcavity can directionally move it for the late collected process.The theoretical analysis and simulation results of this paper had important reference values for building a new type spherical double fiber optical tweezers system platform,and also making adequate theories and preparation of experiment for the next large-scale environment monitoring production and the haze dust equipment.