大气湍流中涡旋光束轨道角动量谱的扩散及修正的研究
发布时间：2018-11-28 11:22
【摘要】：自Allen在1992年指出涡旋光束具有轨道角动量(orbital angular momentum,OAM)以来,人们对涡旋光束在各个领域的应用产生了极大的兴趣。由于涡旋光束所携带的OAM量子数可为任意整数,因此理论上每一种涡旋光束可具有无穷多个OAM特征模。另外,涡旋光束各个OAM特征模之间的正交性有利于进行高速率的数据传输。近年来的研究表明,涡旋光束在大气通信中具有巨大的应用潜力。然而,OAM在大气湍流的影响下可能会发生严重的扩散,并进而在通信中产生严重的串扰。事实上,OAM扩散的产生降低了通信质量,并限制了通信距离。目前已经找到了一些行之有效的方法以改善通信质量,如自适应光学等。总体来说,基于OAM的大气光通信现在仍处于探索阶段。本文主要做了以下几方面的工作:1、研究了一种名叫环形光束(circular beam,CiB)的涡旋光束在大气湍流中的传播特性。研究结果表明当CiB的参数为某些特殊值时,CiB可具有会聚特性并进而使得OAM模在大气湍流中呈现出自动的恢复效应,这意味着OAM扩散可发生逆转。这一发现可提高初始OAM态的检测概率,有利于改善通信质量。2、证实了二维叠加OAM态在大气湍流中可以表现出协同效应。协同效应意味着二维叠加OAM态的检测概率大于它的任一部分所表示的OAM本征态。另外通过分析发现协同效应主要来源于二维叠加OAM态的两个OAM量子数互相变化的概率。当这一概率减小时,协同效应变弱甚至消失。3、讨论了大气湍流中的旋转相关函数,并发现了具有任意波函数的OAM本征态在大气湍流的弱浮动区域中传播时其转变为其他OAM本征态的概率都具有一个固定上限。初始OAM本征态转变为一个特定OAM本征态的概率上限仅取决于初始态的OAM量子数。4、研究了纠缠OAM光子对在大气湍流中的特性。纠缠OAM光子对的制备来源于自发参量下转换的方法。在这一方法中,泵浦光源用OAM模叠加而成。仿真结果表明,当接受态的波函数与泵浦光源的复振幅函数相一致时,检测概率最大。另外对于纠缠情形,二维叠加OAM态的检测概率略大于OAM本征态的检测概率,并且这一差值在较强的湍流中更为明显。
[Abstract]:Since Allen pointed out that vortex beams have orbital angular momentum (orbital angular momentum,OAM) in 1992, people have been interested in the applications of vortex beams in various fields. Since the OAM quantum number carried by a vortex beam can be an arbitrary integer, each vortex beam can theoretically have infinite OAM eigenmodes. In addition, the orthogonality of each OAM characteristic mode of vortex beam is favorable for high rate data transmission. Recent studies have shown that vortex beams have great application potential in atmospheric communications. However, under the influence of atmospheric turbulence, OAM may have serious diffusion and serious crosstalk in communication. In fact, the OAM diffusion reduces the communication quality and limits the communication distance. At present, some effective methods have been found to improve the communication quality, such as adaptive optics. In general, atmospheric optical communication based on OAM is still in the exploration stage. The main work of this paper is as follows: 1. The propagation characteristics of a vortex beam called annular beam (circular beam,CiB) in atmospheric turbulence are studied. The results show that when the parameters of CiB are some special values, CiB can have convergence characteristics and make the OAM model show an automatic recovery effect in atmospheric turbulence, which means that the OAM diffusion can be reversed. This discovery can improve the detection probability of the initial OAM state and improve the communication quality. 2. It is proved that the two-dimensional superposition OAM state can exhibit synergistic effect in atmospheric turbulence. The synergistic effect means that the detection probability of two-dimensional superposition OAM states is greater than the OAM eigenstates represented by any of its parts. In addition, it is found that the synergistic effect is mainly derived from the probability that two OAM quantum numbers of two dimensional superposition OAM states change each other. When the probability decreases, the synergistic effect becomes weak or even disappears. 3. The rotational correlation function in atmospheric turbulence is discussed. It is also found that the probability of transition to other OAM eigenstates of OAM eigenstates with arbitrary wave functions in the weakly floating region of atmospheric turbulence has a fixed upper limit. The upper limit of the probability of the transition of the initial OAM eigenstate to a specific OAM eigenstate depends only on the OAM quantum number of the initial state. The properties of entangled OAM photon pairs in atmospheric turbulence are studied. The preparation of entangled OAM photon pairs originates from the spontaneous parametric downconversion method. In this method, the pump source is superposed by OAM mode. The simulation results show that the detection probability is the highest when the wave function of the receiving state is consistent with the complex amplitude function of the pump light source. In addition, for entanglement case, the detection probability of two-dimensional superposition OAM state is slightly higher than that of OAM intrinsic state, and the difference is more obvious in strong turbulence.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1
本文编号：2362686
[Abstract]:Since Allen pointed out that vortex beams have orbital angular momentum (orbital angular momentum,OAM) in 1992, people have been interested in the applications of vortex beams in various fields. Since the OAM quantum number carried by a vortex beam can be an arbitrary integer, each vortex beam can theoretically have infinite OAM eigenmodes. In addition, the orthogonality of each OAM characteristic mode of vortex beam is favorable for high rate data transmission. Recent studies have shown that vortex beams have great application potential in atmospheric communications. However, under the influence of atmospheric turbulence, OAM may have serious diffusion and serious crosstalk in communication. In fact, the OAM diffusion reduces the communication quality and limits the communication distance. At present, some effective methods have been found to improve the communication quality, such as adaptive optics. In general, atmospheric optical communication based on OAM is still in the exploration stage. The main work of this paper is as follows: 1. The propagation characteristics of a vortex beam called annular beam (circular beam,CiB) in atmospheric turbulence are studied. The results show that when the parameters of CiB are some special values, CiB can have convergence characteristics and make the OAM model show an automatic recovery effect in atmospheric turbulence, which means that the OAM diffusion can be reversed. This discovery can improve the detection probability of the initial OAM state and improve the communication quality. 2. It is proved that the two-dimensional superposition OAM state can exhibit synergistic effect in atmospheric turbulence. The synergistic effect means that the detection probability of two-dimensional superposition OAM states is greater than the OAM eigenstates represented by any of its parts. In addition, it is found that the synergistic effect is mainly derived from the probability that two OAM quantum numbers of two dimensional superposition OAM states change each other. When the probability decreases, the synergistic effect becomes weak or even disappears. 3. The rotational correlation function in atmospheric turbulence is discussed. It is also found that the probability of transition to other OAM eigenstates of OAM eigenstates with arbitrary wave functions in the weakly floating region of atmospheric turbulence has a fixed upper limit. The upper limit of the probability of the transition of the initial OAM eigenstate to a specific OAM eigenstate depends only on the OAM quantum number of the initial state. The properties of entangled OAM photon pairs in atmospheric turbulence are studied. The preparation of entangled OAM photon pairs originates from the spontaneous parametric downconversion method. In this method, the pump source is superposed by OAM mode. The simulation results show that the detection probability is the highest when the wave function of the receiving state is consistent with the complex amplitude function of the pump light source. In addition, for entanglement case, the detection probability of two-dimensional superposition OAM state is slightly higher than that of OAM intrinsic state, and the difference is more obvious in strong turbulence.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1
【参考文献】
相关期刊论文 前1条
1 刘义东;高春清;高明伟;;Study on holographic grating diffraction for Laguerre Gaussian beam generation[J];Chinese Physics B;2008年05期
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