Tightly Focused Light Field Regulation And Its Application In Dynamic Optical Capture

In the field of micromanipulation,optical tweezers is a relatively mature tool,which will capture and manipulate tiny particles in the micro world.Because it uses the radiation pressure and single beam gradient force trap forcing the surface of particles,which will produce force,thus limiting the spatial position of the particles.Therefore,it has the advantages of Sub-contact,non-invasive,targeting and so on.The invention of optical tweezers greatly promoted the development of atomic physics,dispersion system and other fields,especially the research of microorganisms,organelles,DNA and other particles in life science.In the diversified development of optical tweezers technology,holographic optical tweezers technology is the most important development direction.By changing the light field distribution of the outgoing light by modulating the amplitude,phase and polarization of the incoming light,SLM can modulate the laser and.One of the characteristics of holographic optical tweezers is producing array optical tweezers or dynamic optical tweezers,so that it can manipulate the movement of multiple particles randomly,which makes the use value of optical tweezers further improved.The work of this paper is as follows:1.Based on the Vector Rayleigh Sommerfeld(VRS)diffraction theory,we design a polygonal phase zone plate and study its focusing characteristics.A method of using different polygonal phase zone plates and different polarized light to produce special focusing spot in 4Pi focusing system is proposed.The phase zone plates(circular,hexagonal and octagonal)composed of different polygonal concentric zones are designed.Different polarized light(linearly polarized light,radially polarized light and angularly polarized light)incident on the designed polygonal phase zone plate with different shapes will produce focusing spot,we have numerically simulated them.During the process,it is found that the polygonal phase zone plate can change the shape of the focus spot,and there are many focus sidelobes around the focus spot.Further research shows that in 4Pi focusing system,three-dimensional focusing spots with special shapes such as "doughnut" shape,hexagon hollow "nut" shape and "gourd" shape can be produced.The results of this study are helpful to enhance the understanding of vector focusing spot,and have potential application value in the fields of optical micromanipulation,laser processing,super-resolution imaging,high-density data storage and so on.2.According to Damman coding method and array phase modulation,we design a three-dimensional array optical tweezers system,which can realize the 3D capture of multiple small balls.Theoretical simulation and experimental results show that the combination of continuous phase two-dimensional Damman coded grating and Damman band plate can produce three-dimensional Damman array spot at the focusing field of high numerical aperture lens.The 3 × 3 × 3 three-dimensional array capture and 5 × 5 two-dimensional array capture of silica microspheres can be realized by using this three-dimensional array spot in the self-made optical tweezers experimental system.3.Multifocus generation based on complex amplitude coding and its experimental study in particle transport.Based on complex amplitude coding generate dynamic multifocus optical: Firstly,we simulate the motion path of multiple particles.Each position of particle motion has a corresponding phase map.After multiple phase maps are continuously loaded into SLM by software,the multifocus array spot can be dynamically controlled.The dynamic optical capture and manipulation of polystyrene microspheres are realized by selecting the sample position without the interference of impurity particles in the field of vision of the display and fine tuning the displacement table.