共查询到18条相似文献，搜索用时 62 毫秒
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利用衍射光栅探测涡旋光束轨道角动量态的研究进展 总被引：1，自引：0，他引：1
涡旋光束是一种携带有轨道角动量的光束,在光学扳手、光通信、旋转探测等领域具有重要的应用价值.由于轨道角动量态是涡旋光束的特征值,因此如何探测光束的轨道角动量态分布至关重要.国内外学者已经提出了多种探测涡旋光束的技术,如干涉法、衍射光栅法、多普勒分析法、超材料表面法等.这些技术中,衍射光栅测量法较为简单易行,应用较广.本综述主要介绍了几种当前利用衍射光栅测量涡旋光束轨道角动量态的主流方法,同时也介绍了如何利用衍射光栅来测量光束的轨道角动量谱. 相似文献
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具有轨道角动量光束入射下的单球粒子散射研究 总被引：1，自引：0，他引：1
根据广义Mie理论,研究了具有轨道角动量拉盖尔-高斯光束（LGB）的空间传输特性以及单粒子散射特性.在单体球粒子对高斯光束散射研究的基础上,分析了在自由空间不同传输距离LGB光束的光强分布情况,在不考虑散射和波束相移关系的情况下,将LGB作为入射高斯光束,通过对波束入射时的散射衰减截面求解得到波束因子,利用矢量球谐函数对入射高斯波束进行展开,从而研究了单球粒子在在轴条件下对具轨道角动量高斯波束入射的散射问题.通过数值计算,讨论了散射强度及角分布在不同波束宽度情况下对其散射特性的影响,并与平面波的情况做了对比.结果表明,当波束束腰半径较小时,束腰半径对衰减率的影响较大,而当束腰半径远大于粒子半径时,接近于平面波的情况.关键词：广义Mie理论轨道角动量Laguerre-Gauss光束单球粒子 相似文献
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光子轨道角动量量子态具有高维和光学涡旋特性, 在经典和量子领域展示出了巨大的应用潜力, 目前对其的研究已成为物理学的一个热点. 本实验研究了利用Sagnac干涉仪干涉的方法将具有不同轨道角动量的光束无破坏地分离到不同的路径, 即实现光子轨道角动量分束器. 实验中利用此分束器验证了对几种不同轨道角动量态(包含叠加态)的分离, 得到了与理论预期相符的实验结果. 这种对轨道角动量态的区分的方法相比已有的其他区分方法具有较好的稳定性, 而且可用于区分叠加态, 也可以达到单光子水平, 最重要的是实现了不同的轨道角动量本征态无破坏的与路径比特耦合. 这种新方法对高密度通信、量子纠缠、量子保密通信、量子计算与量子信息等方面有着重要的意义. 相似文献
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当光束在海洋中传输时,湍流的存在会严重影响光束的质量,导致接收端光场产生扭曲和退化现象。为解决该问题,提出一种基于改进深度可分离网络（IXception）的方法,用于实现通过海洋湍流传输的涡旋光束轨道角动量模态识别。采用分步相位屏的思想,基于功率谱反演法仿真涡旋光束在海洋中的传输过程,并建立入射光场发生的退化、扭曲的散斑场数据集,用数据集来训练IXception识别散斑场中涡旋光束的轨道角动量。IXception延用Xception架构思想,结合了残差结构和倒置残差结构,能够提取高度空间深度特征,减少网络结构参数的冗余,增强泛化能力。研究结果表明,IXception在20 m和80 m湍流中对扭曲光场轨道角动量的识别率达到了99.20%与97.9%。随着传输距离的增加,IXception的识别率会略有降低,但与Xception模型相比,IXception识别性能更好。 相似文献
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从傍轴条件下光束轨道角动量的基本理论出发,根据高阶椭圆厄密–高斯光束的光场分布,运用张量方法,对高阶椭圆厄密-高斯光束轨道角动量的密度分布进行了理论分析,得到了求解该密度分布的计算公式,并在给定参量条件下作了数值模拟.进一步对光束中每个光子携带的平均轨道角动量进行了计算,发现其值随着椭圆厄密-高斯光束阶次的增大而增大,表明高阶椭圆厄密-高斯光束能够比椭圆高斯光束或拉盖尔-高斯光束提供高得多的轨道角动量. 相似文献
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携带轨道角动量的汉克-贝塞尔(Hankel-Bessel,HB)光束具有无衍射和自聚焦特性,用来作为信息传输的载体有望增大信息传输容量.基于Rytov近似理论,推导得到了HB涡旋光束经过海洋水平弱湍流信道后的螺旋相位谱的解析表达式,并利用数值仿真方法研究了海洋湍流参数对轨道角动量模式探测概率的影响.结果表明,海洋湍流导致发射轨道角动量模式的探测概率下降,出现模式串扰和螺旋相位谱扩展.海洋湍流对HB涡旋光束的负面影响随着轨道角动量模式数、传输距离、温度方差耗散率的增加而增强,随湍流动能耗散率的增加而减弱.HB涡旋光束受以盐度波动驱动的海洋湍流的负面影响更大.另外,在弱湍流及几十米传输距离条件下,HB涡旋光束的传输性能要差于最佳束腰大小设置的拉盖尔-高斯涡旋光束.这些结果有望为海洋环境水下光通信链路的实现提供一定的参考价值. 相似文献
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传统的螺旋相位板是一种利用沿方位角方向介质材料高度递增实现对光束相位调控产生涡旋光束的光学器件,由于这种特殊的几何结构特征使其不能通过相位板的叠加而调控出射光束所携带的角量子数.本文基于坐标变换方法将介质材料沿方位角方向折射率不变而高度递增的传统螺旋相位板变换为一种介质材料沿方位角方向高度不变而折射率递增的平板式螺旋相位板.通过理论分析与数值模拟,发现本文所设计的平板式螺旋相位板不仅与传统螺旋相位板一样能够产生高质量的涡旋光束,而且平板式螺旋相位板的高度和涡旋光束携带的角量子数可以根据介质材料的折射率选取而任意调节.为了实际应用的需要,可以通过叠加多层平板式螺旋相位板以获得不同角量子数的涡旋光束.这种平板式螺旋相位板在光传输、光通信等领域具有广阔的潜在应用价值. 相似文献
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Laguerre-Gaussian beams, as a special model with spiral phase structure, have been intensively investigated. Holographic grating method is a convenient method of generating Laguerre-Gaussian beams and measuring their orbital angular momenta. But due to some inevitable adverse factors such as lateral displacement, angular deflection and elliptical incident profile of incident beam, the practical effectiveness should be reevaluated. This paper is devoted to the study on the influences of the abovementioned three adverse factors on the holographic grating method. The characteristics of the mode decomposition of diffractive order and the relative powers of the orbital angular momentum eigen-states are also given. 相似文献
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It is well known that photons not only carry linear momentum, but also have spin angular momentum related to polarization and Orbital Angular Momentum （OAM） linked with spiral phase. In addition, Spatiotemporal Optical Vortices （STOVs） carrying transverse OAM bring emerging research interests to the optical field. In this paper, we studied the characteristics of tightly focused scalar STOVs and the controllability of OAM orientation in the focused wavepacket. For an incident spatiotemporal wavepacket, which has three mutually orthogonal OAM, including two transverse OAMs and one longitudinal OAM, the corresponding focused wavepacket on the focal plane will collapse due to the spatiotemporal astigmatic effect of the high numerical aperture lens. Based on the modes conversion principle of the cylindrical lens, the incident spatiotemporal wavepacket is preconditioned. And the preconditioned spatiotemporal wavepacket will produce an intact focused wavepacket with a spiral phase in spatiotemporal plane. Debye integral is used to simulate and analyze the characteristics of tightly focused spatiotemporal wavepackets. The numerical simulation results of the preconditioned incident wavepacket show that it is split into two independent parts, the intensity is mainly distributed in the x-t plane and y-t plane, and both of these two planes exhibit binarized phase distributions. In the x-y plane, the phase abruptness caused by the preconditioning gives rise to discontinuous phase distribution in the range of ![]()
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x-t and y-t plane vary continuously from -π to π along the counterclockwise direction, indicating that the topological charge of the transverse OAM in these two planes is +1. In the x-y principle plane, five dark areas appear and each area corresponds to a phase singularity. In the central dark area, the phase varies continuously from -π to π along the clockwise direction, while in the other four dark areas, their phases vary continuously from -π to π along the counterclockwise direction. Thus, the OAM topological charge of the central vortex is -1 and the OAM topological charge of the four peripheral vortices is +1, which is caused by the spatiotemporal coupling. To further analyze the complex coupling phenomenon, the tightly focusing process can be regarded as a Fourier transform of the incident field.According to the expression of the incident field on the principle plan, it can be divided into three parts. The Fourier transformation of the first part will result in two pulse along the x -axis in the focal region, the Fourier transformation of second part will result in two pulse along the y -axis in the focal region, and the Fourier transformation of third parts will produce a highly confined vortex of topological charge of +1 in the focal region. Based on the principle of Fourier transformation, the Fourier transformation of the product of the above three terms is equal to the convolution of their respective Fourier transformations. The convolution of shifted pulse and highly confined vortex will result in the shift of the vortex. Thus, five phase singularities are generated by the complex coupling during the tightly focusing process. Meanwhile, to demonstrate the three-dimensional spatiotemporal evolution trajectory of the phase singularity, we extract the hollow structure inside the focused wavepacket. From the result, we find that the spatiotemporal coupling in the center of the focused wavepacket is stronger than in the peripheral region. We also calculate the topological charge of the OAM within different slices of the focused wavepacket to quantitatively analyze the effect of the spatiotemporal coupling on each kind of OAM. The numerical results show that, the spatiotemporal coupling has few effects on the longitudinal OAM of the focused wavepacket, which provides the possibility to control the focused wavepacket OAM orientation by adjusting the topological charge of the longitudinal OAM in the incident wavepacket. Different topological charge （![]()
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《等离子体物理论文集》2017,57(9):404-413
A generalized response (dielectric) function for twisted electrostatic waves is derived for an un‐magnetized self‐gravitating thermal dusty plasma, whose constituents are the Boltzmann‐distributed electrons and positive ions in the presence of negatively charged micrometre‐sized massive dust particulates. For this purpose, a set of Vlasov–Poisson coupled equations is solved along with the perturbed Laguerre–Gauss distribution function, as well as the electrostatic and gravitational potentials in the limit of paraxial approximation. For plane wave solution, the wavefronts of the dust‐acoustic (DA ) wave are assumed to have a constant phase with electric and gravitational field lines propagating straight along the propagation axis. On the other hand, non‐planar wave solutions show helical (twisted) wavefronts, in which field lines spiral around the propagation axis owing to the azimuthal velocity component to account for the finite orbital angular momentum (OAM ) states. The dispersion relation and damping rate for twisted DA waves are studied both analytically and numerically. It is shown that finite OAM states, the dust to electron temperature ratio, and dust self‐gravitation effects significantly affect the linear dispersion and Landau damping frequencies. In particular, the phase speed of twisted DA waves is reduced with the variation of the twist parameter η (= k /lqϕ ), dust concentration δ (= nd 0/ni 0), and dust self‐gravitation α (= ωJd /ωpd ). The relevance of our findings to interstellar dust clouds is also discussed for micrometre‐sized massive dust grains. 相似文献
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Matt M. Coles Mathew D. Williams Kamel Saadi David S. Bradshaw David L. Andrews 《Laser u0026amp; Photonics Reviews》2013,7(6):1088-1092
A chiral arrangement of molecular nanoemitters is shown to support delocalised exciton states whose spontaneous decay can generate optical vortex radiation. In contrast to techniques in which phase modification is imposed upon conventional optical beams, this exciton method enables radiation with a helical wave‐front to be produced directly. To achieve this end, a number of important polarisation and symmetry‐based criteria need to be satisfied. It emerges that the phase structure of the optical field produced by degenerate excitons in a propeller‐shaped array can exhibit precisely the sought character of an optical vortex – one with unit topological charge. Practical considerations for the further development of this technique are discussed, and potential new applications are identified. 相似文献
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Mengna Jiang Yan Chen Fei Zhang Mingbo Pu Yinghui Guo Mingfeng Xu Weisheng Yue Qiong He Ping Gao Xiangang Luo 《Advanced Optical Materials》2024,12(2):2301314
Light beam carrying spin angular momentum (SAM) and orbital angular momentum (OAM) have attracted great interest due to their great potential for high-capacity optical communication, optical tweezers, and quantum information. However, the current detection methods suffer from the lack of robustness to misalignments in the optical system, which limits the detection accuracy and the application for off-axis vortex array detection. Here, a high-efficiency, broadband, and single-layer metasurface design is proposed for alignment-free angular momentum detection via spin-independent astigmatic transformation (SIAT). The SAM and OAM states can be recognized from the diffraction direction and patterns, respectively. Proof-of-concept demonstrations are experimentally carried out on different incident beams including circular-polarization, linear-polarization, and vector vortex beams, as well as vortex beam arrays, showing a high diffraction efficiency of ≈81% at 1064 nm while operating within the broadband region of 900–1300 nm. The alignment-free merit for the incident position, incident angle, and detector distance grants the device great potential for integrated quantum systems and multiparticle micromanipulation with optical tweezers. 相似文献