Investigation On The Characterization, Propagation And Application Of A Partially Coherent Cylindrical Vector Beam

In the past several years, cylindrical vector beam has been widely investigated due toits unique tightly focusing properties and has important applications in many fields, such asoptical trapping, laser making, dark field imaging and data storage, etc. To achieve specialtightly focusing spots, it needs to make amplitude or phase modulation to the incidentcylindrical vector beam.In some fields, such as material thermal processing, target surface radiation of inertialconfinement fusion, it needs to decrease the coherence of light to make the light energydistribution more homogeneous. Up to now, investigation of partially coherent beam ismainly focused on the uniformly polarized beam. Few people study the partially coherentcylindrical vector beam.In this thesis, we will modulate the coherence of cylindrical vector beam, andintroduce a theoretical mode of partially coherent cylindrical vector beam based on thecoherent cylindrical vector beam mode. The paraxial and nonparaxial propagationproperties are investigated. The experimental generation methods of partially coherentcylindrical vector beams are also introduced. The tightly focusing properties and theradiation forces on Rayleigh particles of a partially coherent azimuthally polarized beampassing through a high numerical aperture lens are studied, and the effect of spatialcoherence on optical trapping is illustrated. In the end, the radiation forces of tightlyfocused cylindrical vector pulse beams on Rayleigh particles are also investigated.In chapter1, we introduce the background of cylindrical vector beam, partiallycoherent beam, and optical tweezers. The main content and originality of this thesis arealso presented.In chapter2, we introduce the light propagation theory, scalar and vector tightlyfocusing theory when passing through a high numerical aperture lens.In chapter3, we have proposed a theoretical model to describe cylindrical vector partially coherent beam, and have studied its paraxial propagation properties. We havefound that the properties of a cylindrical vector partially coherent beam on propagation aremuch different those of a cylindrical vector coherent beam. By degrading the coherence ofa cylindrical vector beam, we can shape the beam profile of such beam, and alter itspolarization structure.In chapter4, we have derived analytical propagation formula of a nonparaxialcylindrical vector partially coherent field in free space. Our numerical results show thatwhen the beam width is much larger than the wavelength, the results calculated bynonparaxial propagation formulae agree well with that calculated by paraxial propagationformulae. When the beam width is comparable to the wavelength, significant differencesbetween paraxial and nonparaxial results appear. By varying the initial correlationcoefficients, one can modulate the statistical properties of a nonparaxial cylindrical vectorpartially coherent field. Furthermore, we also derived the analytical formula of the degreeof paraxiality of a partially coherent cylindrical vector beam. Our results show that thedegree of paraxiality of a partially coherent cylindrical vector beam is mainly determinedby beam waist, initial coherence and beam orders.In chapter5, we have experimentally generated partially coherent cylindrical vectorbeams. The focusing properties of partially coherent cylindrical vector beams withdifferent spatial coherence passing through a thin lens are also experimentally investigated.The experimental results agree well with theoretical predictions.In chapter6, the expressions of a partially coherent azimuthally polarized fieldfocused by a high numerical aperture lens near the focus have been derived. The effects ofspatial coherence on the intensity distribution have been illustrated numerically, and it wasfound that the beam spot of a tightly focused azimuthally polarized beam can be shaped byvarying the spatial coherence. Furthermore, the radiation forces on Rayleigh particlesinduced by a tightly focused partially coherent azimuthally polarized beam are also studied.It is found that a Rayleigh particle whose refractive index is larger or smaller than that ofthe ambient can be trapped by varying the initial spatial coherence of incident partiallycoherent azimuthally polarized field. In chapter7, we have investigated the dynamic radiation force produced by tightlyfocused cylindrical vector pulses acting on Rayleigh particles. It is found that the radiationforces of tightly focused cylindrical vector pulses increase greatly with the pulse durationdecreasing. The particles can be trapped stably both in transverse and longitudinal directionby radially polarized pulse, and can be trapped stably in transverse direction byazimuthally polarized pulse. We also find that the radiation forces of tightly focused linearpolarized pulse with short pulse duration are much different from cylindrical vector pulses.It may be used for accelerating the small particle in longitudinal direction.In chapter8, the conclusion of this thesis is drawn and some prospects are illustrated.