Multi-dimensional Arrangement Of Particles Based On High-order Mode Beam And Its Key Technology Research

Since the optical tweezers technology was proposed,it has shown excellent application prospects in single-particle research fields such as biology,physics,and chemistry.In the past few decades,researchers have continued to study optical tweezers technology,making the single-particle capture technology gradually mature.With the in-depth research in many fields such as biosensing and biomedicine,single particle capture has been unable to meet the needs of research,so the development of optical tweezers capable of capturing and arranging multiple particles is becoming more and more important.Holographic optical tweezers and interferometric optical tweezers have been developed to capture and align multiple particles.Holographic optical tweezers,interferometric optical tweezers and other methods need to use the traditional lens system to capture and arrange particles,but the traditional optical tweezers have complex optical path,short working distance and other shortcomings,these shortcomings limit the convenience of the traditional optical tweezers system in practical application.In order to further improve the flexibility of optical tweezers,scholars have made great efforts in the field of optical fiber tweezers,and developed many optical fiber tweezers that can realize one-dimensional and two-dimensional arrangement of particles.However,in the field of fiber optic tweezers,it is still difficult to achieve multi-dimensional contactless capture and alignment of particles with a single fiber optic tweezer.In recent years,the application of Bessel beam in single fiber optical tweezers makes it no longer necessary to maintain contact trapping for multi-particle and one-dimensional arrangement,which makes it possible to realize multi-dimensional contactless arrangement of particles by using single fiber optical tweezers.This thesis proposes a single-fiber optical tweezers scheme based on the high-order Bessel-like beams,which realizes the multi-dimensional non-contact capture and arrangement of particles.The fiber probe is composed of three parts:a few-mode fiber,a multi-mode fiber and a glass microsphere.When the high-order mode is excited in the few-mode fiber,the coaxial welding of the few-mode fiber and the multi-mode fiber can be used to excite the high-order Bessel-like beams on the end of the multi-mode fiber.The high-order Bessel-like beams are further converged and shaped using glass microspheres to construct a multi-dimensional arrangement of convergence points in space,thereby realizing the multi-dimensional non-contact capture and arrangement of particles.In this thesis,simulation software is used to design and optimize the structure parameters of the proposed probe,and numerical calculation methods are used to analyze and calculate the optical trap force and the trapping potential energy of the optical fiber optical tweezers exerted on the particles.It is theoretically proved the fiber optical tweezers have the possibility of realizing multi-dimensional arrangement of particles.In the experiment,the fiber optical tweezers probe was made,and the fiber optical tweezers experimental system was built.Through the method of staggered butt connection of fiber cores,different modes of light were excited in the few-mode fiber to generate Bessel-like beams with different energy distributions.In the step mode,glass microspheres are further used to shape and converge the Bessel-like beams,so that one-dimensional,two-dimensional,and three-dimensional arrangements of particles are realized experimentally.When only the LP₀₁ mode is incident,the particles can be captured at three positions on the fiber axis and arranged in a one-dimensional line;when LP₀₁and LP₁₁ are incident at the same time,the particles can be captured outside the fiber axis based on the one-dimensional arrangement.So as to realize the two-dimensional arrangement of the particles;when the three modes of LP₀₁,LP₁₁ and LP₂₁ are incident at the same time,the particles can be captured in different planes,so as to realize the three-dimensional arrangement of the particles.And the capture stability of the fiber optical tweezers was measured in the experiment.Compared with the existing methods,the single-fiber optical tweezers proposed in this thesis can achieve non-contact multi-dimensional capture and arrangement of particles,and have a certain versatility.They have potential application value in the study of biological processes such as cell communication,tissue and organ formation,preparation of biophotonic waveguides and other fields.