多涡旋光的传输建模与特性分析

发布时间：2018-08-25 18:43

【摘要】：涡旋光束(Vortex Beams)是指光束具有螺旋型的波前,并且光束的中心处的光强分布为零,这一特性也被称为相位奇点。涡旋光束具有轨道角动量(Orbital Angular Momentum,简记为OAM),利用轨道角动量可以对信息进行编码,基于这一特性可将其应用于自由空间的光学通信系统。轨道角动量的复用是一种特殊的空分复用。由于具有不同拓扑电荷数的OAM模式在空间中具有正交性,且理论上其拓扑荷可取无穷个,在通信系统中利用OAM光束作为信息载体的研究逐步引起广泛关注。目前国内外学者对于涡旋光束的研究逐渐深入,近年来,涡旋光束已经在诸多领域发挥着相当重要的作用,例如微粒子的囚禁、捕捉与旋转,生物医学以及自由空间中的光学传输系统。本文围绕着涡旋光束的传输特性进行了建模以及仿真研究,主要内容包括如下几个方面。(1)简述了涡旋光束的概念,重点介绍了国内外对于涡旋光束的研究历史,以及研究现状,对于涡旋光束的应用以及存在潜在价值的领域前景作了展望。(2)介绍了研究涡旋光束的理论方法,通过对比研究了整数阶以及分数阶单涡旋光束的传输特性,并分别模拟出其光强分布。通过仿真显示整数阶涡旋光束在传输过程中能够保持稳定性。(3)在单涡旋光束的基础上,对多涡旋光束进行建模仿真,推导出多涡旋光束的光强分布以及传输演变特性。(4)重点研究两束单涡旋光束共轴叠加形成双涡旋光束,通过研究双涡旋光束在传输一段距离后的光强分布,利用理论推导出双涡旋光束的光强分布随传输距离的关系,通过MATLAB模拟仿真来研究不同拓扑荷值的双涡旋光束的光斑特性。固定外环拓扑荷数,不断增大内环拓扑荷数,研究双涡旋光束中两束涡旋光束的光强分布图的变化。经研究发现,随着传输距离的增大,整数阶双涡旋光束的光强分布依然能够维持圆对称分布,相位奇点能够完整保留,仅仅存在着光斑的扩束现象,且叠加后的两束涡旋光束在传输过程中仍然保持着相互独立传输。
[Abstract]:The vortex beam (Vortex Beams) refers to the wave front of the beam with helical shape, and the intensity distribution of the beam at the center of the beam is zero, which is also known as the phase singularity. The vortex beam has orbital angular momentum (Orbital Angular Momentum,) which is abbreviated as OAM), which can encode the information using orbital angular momentum. Based on this property it can be applied to optical communication systems in free space. Orbital angular momentum multiplexing is a special space division multiplexing. Because OAM modes with different topological charge numbers have orthogonality in space and their topological charges are infinite theoretically, the study of using OAM beams as information carriers in communication systems has gradually attracted wide attention. In recent years, vortex beams have played an important role in many fields, such as the trapping, trapping and rotating of microparticles. Biomedical and optical transmission systems in free space. In this paper, the propagation characteristics of vortex beam are modeled and simulated. The main contents are as follows: (1) the concept of vortex beam is briefly introduced, and the research history and present situation of vortex beam at home and abroad are emphatically introduced. The applications of vortex beams and the prospect of potential applications are prospected. (2) the theoretical methods for studying vortex beams are introduced. The propagation characteristics of integer and fractional order single vortex beams are studied by comparison. The light intensity distribution is simulated respectively. The simulation results show that the integer vortex beam can maintain stability in the process of propagation. (3) on the basis of single vortex beam, the multi-vortex beam is modeled and simulated. The light intensity distribution and propagation evolution characteristics of multi-vortex beams are derived. (4) the co-axial superposition of two single-vortex beams to form a double-vortex beam is emphasized, and the intensity distribution of the double-vortex beam after a certain distance is studied. The relationship between intensity distribution and propagation distance of double vortex beam is derived theoretically. The speckle characteristics of double vortex beam with different topologies are studied by MATLAB simulation. The topological charge number of the outer ring is fixed and the topological charge number of the inner ring is increased continuously. The variation of the intensity distribution of the two vortex beams in the double vortex beam is studied. It is found that with the increase of propagation distance, the intensity distribution of integer order double vortex beams can still maintain circular symmetry distribution, the phase singularity can be completely preserved, and there is only the phenomenon of beam expansion. Moreover, the superimposed two vortex beams are still propagating independently.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

【参考文献】