Three-dimensional Design And Manipulation Of Optical Focal Fields

The extraordinary properties of vector optical fields and the capability of shaping the focal field via manipulation of vector optical fields have attracted an increased interest and been extensively explored in recent years.In particular,the three-dimensional multifocal arrays can find important application in many fields such as parallel particle trapping,parallel multiphoton microscopy imaging,parallel recording and parallel laser acceleration.For example,three-dimensional optical cage arrays can effectively parallelly capture particles of low refractive index;three-dimensional vector multifocal arrays for the polarization-based applications such as parallel polarization-multiplexed recording,parallel multiphoton microscopy imaging,parallel polarization information encryption,and so on;three-dimensional perfect vector vortex arrays can be applied in the parallel particle rotation manipulation,parallel quantum information,and so on.However,the research of the three-dimensional focal field is fresh and there remain many scientific and technological problems to be solved.This dissertation is mainly focused on the generation,manipulation and application by the theoretical and experimental ways from the three-dimensional focal field.The main contributions of this dissertation are as follows:1.A scheme by pseudo-periodic phase modulation to generate three-dimensional multifocal arrays is proposed.We reviewed the previous iterative and non-iterative methods to realize the control of the three-dimensional focal fields.Iterative scheme employs Gerchberg-Saxton algorithm to search an optimal solution to achieve the desired focus through modulating the amplitude,phase or polarization of the incident beam.However,iterative methods usually require a huge computational load and may also lead to a non-unique solution occasionally.Among non-iterative schemes,the gratings and lenses based algorithms are the popular choice for producing multiple focal spots;these algorithms resemble the phase effect of gratings and lenses on transverse and axial shifts,respectively,to control the three-dimensional shifting of multifocal spots.However,the multifocal arrays produced by this method usually suffer from problems such as low uniform and less tunable spacing of multiple focal spots.In order to overcome these limitations,we propose a method of pseudo-periodic phase modulation.This method encodes each pixel by a spatial light modulator,enbling each pixel to be loaded proper grating and lens factor to realize the control over three-dimensional position of each focal spot.Futhrmore,we use the macro-pixel sampling method to realize three-dimensional multifocal arrays.We use the pseudo-periodic arrangement between macro pixels for avoiding the nested periodic repetition of entire multifocal arrays.The proposed pseudo-periodic phase modulation can realize three-dimensional multifocal arrays with adjustable focal spot number and distribution shape.2.A design for completely generating three-dimensional vectorial multifocal arrays is developed.This scheme can not only adjust the shape of the three-dimensional vectorial multifocal arrays,but also adjust the polarization distribution of each focal spot,allowing to generate multifocal arrays with complex polarization states ranging from linear polarization to radial and azimuthal polarizations or hyride polarizations.In this scheme,the grating and lens factor is imposed into both of the orthogonal polarized incident component beam,and then after pseudo-periodic encoding of the complex amplitude,the polarization state of each focal spot is determined by the phase difference and the relative amplitude between the two orthogonal components.In this way,the three-dimensional distribution of each focal spot is regulated by the grating and lens factor.Each pixel is not only loaded the respective grating and lens factor,but also loaded the respective two orthogonal polarization components to generate three-dimensional vectorial multifocal arrays.We performed the optical experiments to verify the practicality and reliability of the scheme.3.We propose and simulate a method for generating three-dimensional optical cage in the vicinity of focus by focusing double-ring shaped radially and azimuthally polarized beam.Our study shows that combination of inner ring with azimuthal ly polarized field outer ring with radially polarized field and a pair of lens factor T can produce optical cage with a dark region enclosed by higher intensity.Shape of cage can be tailored by appropriately adjusting the parameters of double-mode beams.Furthermore,multiple three-dimensional optical cages can be realized by applying the pseudo-periodic phase modulation to double-ring shaped radially and azimuthally polarized beam.4.We propose an approach for generating three-dimensional perfect vectorial vortices arrays.We create three-dimensional perfect vectorial vortices arrays with independent of the polarization topological charge and the topological charge of spiral phase,which possess the properties of perfect vortices beam and perfect polarization vortices beam.In this scheme,the grating and lens factor is imposed into both of the orthogonal polarized incident component beams to generate three-dimensional perfect vectorial vortices arrays,the three-dimensional distribution of each perfect vectorial vortex is regulated by the grating and lens factor,and the two orthogonal components control the radius,the polarization topological charge and the topological charge of spiral phase of each perfect vectorial vortex.In order to generate the three-dimensional perfect vectorial vortex arrays,each pixel is not only loaded the respective the grating and lens factor,but also loaded the two orthogonal polarization components.We verify the validity and reliablity of the design method by optical experiments.