【作者】 董一鸣；

【导师】 蔡阳健；

【作者基本信息】 苏州大学 ， 光学， 2014， 博士

【摘要】 近年来，柱偏振矢量光束由于其独特的紧聚焦特性引起了人们的广泛研究。该种光束在光束俘获，激光制造，暗场成像，数据存储等领域中具有重要的应用价值。为了得到特殊的紧聚焦光斑，通常需要对入射的柱偏振矢量光束进行振幅和位相的调控。在某些领域中，例如材料热处理，惯性约束核聚变的靶面辐射等情形下，我们需要降低激光的相干性，使得光斑能量分布更加均匀化。此外，在激光大气光通讯中，低相干性的激光受大气湍流的影响也较完全相干光要小。目前对于部分相干光的研究，主要集中在均匀偏振的光束，很少有人研究部分相干的柱偏振矢量光束。本论文主要对柱偏振矢量光束的相干性进行调控，在完全相干的柱偏振矢量光束模型的基础上，提出了部分相干柱偏振矢量光束的理论模型，并研究了部分相干柱偏振矢量光束的傍轴与非傍轴传输特性。提出了产生部分相干柱偏振矢量光束的实验方案。并研究了部分相干角向偏振光通过高数值孔径透镜后的聚焦特性，研究了紧聚焦后的光束对瑞利微粒的辐射力，讨论了光束相干性对瑞利微粒俘获的影响。另外还研究了柱偏振矢量脉冲光束经过紧聚焦后对瑞利微粒的辐射力。在第一章中介绍了柱偏振矢量光束、部分相干光束和光镊的研究背景，同时介绍了本论文的主要研究内容和创新点。在第二章中介绍了激光的传输理论和通过高数值孔径透镜后的标量和矢量紧聚焦理论。在第三章中，我们提出了部分相干柱偏振矢量光束的理论模型，并且研究了部分相干柱偏振矢量光束的傍轴传输特性。结果表明，在传输过程中，部分相干的柱偏振矢量光束与完全相干情形很不一样。通过调控柱偏振矢量光束的相干性，我们可以控制其光斑形状和偏振结构。在第四章中，我们推导了非傍轴的部分相干柱偏振矢量光束在自由空间中传输的解析表达式。我们的数值结果显示，当光束的腰斑尺寸远大于光束波长时，利用非傍轴的传输公式所得结果与利用傍轴公式的结果基本吻合。而当光束的腰斑尺寸小到可以与波长相比拟时，两者之间就会出现很大的不同。通过改变光束的初始相干性，我们可以调控非傍轴部分相干柱偏振矢量光束的传输特性。另外，我们也推导了部分相干柱偏振矢量光束的傍轴度的解析表达式。结果显示，部分相干柱偏振矢量光束的傍轴度主要与光束的腰斑尺寸、初始相干性和光束的阶数有关。在第五章中，我们在实验上产生了部分相干柱偏振矢量光束，并且研究了不同相干性的柱偏振矢量光束经过薄透镜后的聚焦特性。我们的实验结果与理论预期能够很好的符合。在第六章中，我们推导了部分相干角向偏振光束通过高数值孔径透镜紧聚焦后在焦点附近的光场表达式，并对光束的初始相干性对聚焦特性的影响作了数值分析。结果表明，通过改变入射的角向偏振光束的相干性，可以实现对聚焦光斑的整形。另外我们还研究了紧聚焦后的部分相干角向偏振光对瑞利微粒的辐射力，可以发现，通过改变光束的初始相干性，我们可以俘获折射率比周围介质大或者小的瑞利微粒。在第七章中，我们研究了紧聚焦后的柱偏振矢量脉冲光束对瑞利微粒的辐射力。我们发现辐射力随着脉冲宽度的减小而迅速增大，径向偏振脉冲光束可以同时在横向和纵向稳定地俘获住微粒，而角向偏振光则能在横向稳定地俘获微粒。当脉宽很小时，线偏振脉冲光束对微粒的辐射力与柱偏振矢量脉冲光束情形很不一样，它可以用来纵向加速微粒。在第八章中我们进行了总结和展望。更多还原

【Abstract】 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.更多还原