Manipulation Of The Optical Chiral Focal Field And Its Optical Force Effects

Optical tweezers have become an important tool in various disciplines such as physics,nanotechnology,spectroscopy,nanometer thermodynamics,mechanics of soft materials and biology due to its non-contact and non-damage properties.The principle of optical tweezers is the optical force effect produced by the interaction between the optical focal field and material.Because of its unique focusing effect and adjustable polarization,vectorial optical field has instilled energy into the development of optical manipulation.As a special case,chiral light field has wide applications in the characterization of chiral substances,enantioselective separation,chiral sensing,nonlinear spectral imaging and asymmetric catalysis,etc.According to different application requirements,optical focal field is always essential to be tailored to produce suitable mechanism.Method of exhaustion is traditional design methods for optical field,which has disadvantages such as low efficiency and time consumption.In recent years,the reverse design method of optical field has attracted more and more attention which combining time inversion theory and Richard Wolff vector diffraction theory.This method can effectively produce the high-precision optical field under the diffraction limit,and has important application value in several field such as single molecule imaging,tip enhanced Raman spectroscopy,high resolution optical microscopy,particle capture and manipulation,etc.The innovation of this thesis is as follows: Firstly,we proposed a novel technology to produce complex chiral light field based on optical reverse design method;Secondly,we developed the manipulation technology of nanoparticles based on complex chiral light field.The main contents of this thesis include:1.The optical trapping effects of a diffraction-limited focal field possessing an arbitrary photonic spin and the movement behavior of the trapped nanoparticles were studied.Firstly,to achieve controllable spin axis orientation,the required pupil field is analytically derived through reversing the radiation patterns and experimentally generated with a home-built vectorial optical field generator(VOF-Gen).Secondly,the optical forces and intrinsic torques of a Rayleigh particle with a spherical or ellipsoidal shape and different spatial orientations trapped by tunable photonic spin were calculated.we demonstrate that the interactions between the tunable photonic spin and nanoparticles lead to not only 3D trapping but also precise control of the nanoparticles' movements in terms of stable orientation,rotational orientation,and rotation frequency.2.The optical technique to sort chiral specimens by using of a transverse optical needle field with a transverse spin(TONFTS)was proposed.Firstly,to achieve controllable orientation of both the photonic spin and the optical needle field,the required pupil field of the illumination is analytically derived through reversing the radiation patterns from an array of paired orthogonal electric dipoles located in the focal plane of a 4Pi microscopy and experimentally generated with a home-built VOF-Gen.Secondly,the scattering behavior of the chiral particle is evaluated by the Mie scattering coefficients and the induced optical force from the interaction between the chiral nanoparticle and the TONFTS is calculated under dipole approximation.Numerical results demonstrated that the particles will be sorting by transverse chiral optical force whose direction determined by the handedness of the chiral material.3.The optical force effect of chiral particles interacting with chiral dipole moment were studied.Firstly,the chiral dipole moment with arbitrary orientation is generated based on reversing the radiation field of electric and magnetic dipole pairs in 4? system.Secondly,the chiral forces generated by the interaction between the chiral dipole moment and the chiral particles were investigated,and numerical results demonstrated that the chiral dipole moment can realize the sorting of chiral particles on the transverse plane of the chiral dipole moment.