Generation,Characterization And Application Of Tightly-Focused Vectorial Field

Due to its confined and diverse spatial distribution,high electric field gradient and energy density,the tightly-focused vectorial field(TFVF)has wide potential applicability for optical microscopy,optical storage,laser processing,laser accelerating and optical manipulation.Studying the spatial distribution of TFVF is of great importance for the innovation and extension of related technologies.In this thesis,focused on the TFVF,a series of research including the algorithm that modulates the three-dimensional(3D)TFVF,the methods to generate and measure TFVF,and the applications of TFVF to the optical manipulations are conducted.The majority of the researches are outlined as below: 1.The Debye-Wolf vectorial diffraction integral is extended to rotated coordinates and an improved 3D focal field shaping algorithm is proposed.In holographicoptical tweezers,the 3D optical transport and optical manipulation ofmulti-particles in parallel can be realized by modulating the 3D spatialdistribution of focal field.However,the existing algorithms to shape such fieldsare time-consuming,which make it difficult to manipulate the particles in realtime.In this paper,by extending the Debye-Wolf vectorial diffraction integral torotated coordinate system,an arbitrary tilted-plane(ATP)Gerchberg-Saxton(GS)algorithm is proposed,which can quickly modulate the light field distribution inthe 3D space,so as to manipulate the motion of multiple particles in threedimensions with real-time refresh rate.Comparing with traditional 3D iterativealgorithms,ATP GS algorithm has faster execution speed and can maintainhigh-quality optical field.In addition,the algorithm has been successfully appliedto holographic optical tweezers,realizing real-time manipulation and rotation of7×7 silica microspheres in 3D space by experiments.2.A setup for generation and characterization of tightly-focused vectorial field isdesigned and built.The existing vector beam generation schemes have the defectsof optical path redundancy and low light energy efficiency.This thesis presents anew generation scheme based on compact optical arrangement,which cansimultaneously controls the phase and polarization of the light field.Toexperimentally study the modulated field,the system also integrates two methodsfor characterization of intensity distribution,including the mirror-scanningmethod and fluorescent nano-probe scanning method.In order to circumvent theimpact of photobleaching on the measurement,a modified scanning scheme isproposed in this paper,which can finish the acquisition of 3D optical field data(512×512×100 pixels,2.4?m×2.4?m×2?m)within 14 mins.This method is 100times faster than traditional scanning scheme.To realize automatic collection andreconstruction,a graphic user interface is programed for the instrument.Finally,the system is applied to optimize the doughnut-shaped depletion spot in stimulated emission depletion microscopy.3.The light-induced rotation of particle with various polarized vortex beams isinvestigated and then a method to improve the rotation efficiency is proposed.Under tightly focusing condition,the particles in the vortex beam may besubjected to an additional transverse spin angular momentum(SAM),which leadto spin rotations along a non-axial direction and further complicate thelight-induced motion of the particle.Further study of the complex motion formsof the light-induced rotations will help us understand the physical mechanism ofthe interaction between light and matter.In this thesis,the light-induced rotationof particle in the tightly focused vortex beams with different polarization isstudied by using the T-matrix method.In experiment,I further studied themovement characteristics of calcium carbonate microparticles and polystyrenemicrospheres and analyzed the influence of the polarization state and topologicalcharge of the incident vortex beams on the rotation of the particles.Finally,wedevelop a new method to improve the spinning speed and give the optimumexperimental conditions to observe axial spin rotation,non-axial spin rotation of particles.