西安理工大学自动化与信息工程学院,陕西 西安 710048
阵列光束在大功率激光合成、远距离通信、高质量输出等方面发挥着重要作用。本文利用相位屏法模拟海洋湍流,研究了径向阵列涡旋光束与矩形阵列涡旋光束在具有外尺度的不稳定分层海洋中的传输特性,并将其与单涡旋光束的传输特性进行了对比,分析了三种涡旋光束在海洋湍流中的光强与相位分布。结果表明:两种阵列涡旋光束传输一段距离后不再保持初始的阵列分布,子光束之间会相互影响,产生了干涉条纹。在相同的条件下,单涡旋光束的漂移比两种阵列涡旋光束大,束宽比两种阵列涡旋光束小,而且径向阵列涡旋光束的漂移比矩形阵列涡旋光束大,束宽比矩形阵列涡旋光束小。在较远距离处,单涡旋光束的闪烁指数比两种阵列涡旋光束大,而且矩形阵列涡旋光束的闪烁指数比径向阵列涡旋光束大;在较强湍流和远距离处,三种涡旋光束的束宽逐渐减小。
光通信 阵列涡旋光束 闪烁指数 湍流相位屏 海洋湍流 光束漂移
Author Affiliations
Abstract
School of Information and Control Engineering, China University of Mining and Technology, Xuzhou 221116, China
Toroidal multipole is a special current distribution that has many different characteristics from electric multipole and magnetic multipole distributions. Because of its special properties, the toroidal dipole is a research hotspot in the field of metamaterials and nanophotonics. However, the low scattering of the toroidal dipole moment makes its excitation a challenging task. At present, there are relatively few studies on its specific engineering applications. In this paper, by slotting in the rectangular cavity, the excitation of an equivalent toroidal dipole is successfully achieved over a wide frequency range of 53–58 GHz. Results indicate that under the action of the toroidal dipole, the mode electromagnetic waves transmitted in the rectangular waveguide are converted into vector beams and are radiated outwards. Further adjusting the spatial distribution of the magnetic dipoles in the toroidal dipoles yields results that indicate that the resonance mode in the slot is still dominated by the magnetic toroidal dipole moment, and the electromagnetic waves radiating outward are vortex beams carrying vector polarization. The scattered energy of each dipole moment inside the antenna is calculated. This calculation verifies that the mass of the vector beam and vector vortex beam is closely related to the toroidal dipole supported by this antenna. The proposed structure can be applied to explorations in vortex filtering, in photon entanglement, and in the photonic spin Hall effect.
toroidal dipole vector beams vector vortex beams Chinese Optics Letters
2024, 22(1): 011601
1 西安理工大学自动化与信息工程学院,陕西 西安 710048
2 西安市无线光通信与网络研究重点实验室,陕西 西安 710048
3 陕西理工大学物理与电信工程学院,陕西 汉中 723001
4 陕西科技大学电子信息与人工智能学院,陕西 西安 710021
海洋湍流和光源参数对涡旋光束的信道容量有十分重要的影响。本文根据Rytov近似理论,利用有限外尺度且不稳定分层的各向异性海洋湍流功率谱,并引入xy平面上的两个各向异性因子来研究完美涡旋(PV)光束、拉盖尔高斯(LG)光束和贝塞尔高斯(BG)光束在海洋湍流下的信道容量,数值模拟了束腰半径、接收孔径直径和海洋湍流参数等对三种光束信道容量的影响。数值结果表明:当传输距离在30~70 m时,较小束腰半径(小于4 mm)的PV或者LG光束可获得比BG光束更大的信道容量;但较大束腰半径(大于12 mm)的PV或者LG光束的信道容量却大于BG光束。此外,当束腰半径小于2 mm时,PV光束的信道容量要大于LG和BG光束,表明采用窄束腰半径(小于2 mm)的PV光束相比LG和BG光束可以增大光通信系统的信道容量。本文的研究结果对海洋环境中光通信光源参数的选择具有重要意义。
海洋光学 信道容量 各向异性海洋湍流功率谱 涡旋光束 光学学报
2023, 43(24): 2401004
1 长春理工大学光电测控与光信息传输技术教育部重点实验室,吉林 长春 130022
2 长春理工大学计算机科学技术学院,吉林 长春 130022
在自由光空间通信领域,使用不同束腰半径组合的涡旋叠加光束可以在同一信道开销下传递更多信息。受大气湍流影响涡旋光束会发生相位扰动,进而影响其轨道角动量(OAM)模态识别。现有模型无法准确识别受随机大气湍流影响而发生扰动的OAM叠加光束模态。因此,提出一种基于注意力机制的深度学习识别方法。将注意力机制模块嵌入到VGG-16中,以提升模型对不同状态叠加光束模态的感知性能。另外为模拟湍流的真实状态,利用功率谱反演法模拟大气湍流,并使用次谐波补偿随机湍流屏的低频信息。同时,建立受到随机湍流影响发生相位扰动的OAM叠加光束数据集,利用该数据集训练所提模型。实验结果表明,在未知大气湍流强度条件下,对比传统方法,所提方法对OAM的识别准确率最高提升了4.46%。这表明了该模型对识别OAM叠加光束的有效性,以及良好的鲁棒性和较好的泛化能力,为识别OAM模态提供一种新的方法。
涡旋光束 轨道角动量 注意力机制 深度学习 大气湍流 激光与光电子学进展
2023, 60(23): 2306003
Lang Li 1,2,3Yingchi Guo 1,2,3Zhichao Zhang 1,2,3Zijun Shang 1,2,3[ ... ]Shiyao Fu 1,2,3,*
Author Affiliations
Abstract
1 Beijing Institute of Technology, School of Optics and Photonics, Beijing, China
2 Ministry of Education of the People’s Republic of China, Key Laboratory of Photoelectronic Imaging Technology and System, Beijing, China
3 Ministry of Industry and Information Technology of the People’s Republic of China, Key Laboratory of Information Photonics Technology, Beijing, China
As an inherent degree of freedom, total angular momentum (TAM) of photons consisting of spin angular momentum and orbital angular momentum has inspired many advanced applications and attracted much attention in recent years. Probing TAM and tailoring beam’s TAM spectrum on demand are of great significance for TAM-based scenarios. We propose both theoretically and experimentally a TAM processor enabling tunable TAM manipulation. Such a processor consists of a set of quasi-symmetric units, and each unit is composed of a couple of diffraction optical elements fabricated through polymerized liquid crystals. Forty-two single TAM states are experimentally employed to prove the concept. The favorable results illustrate good TAM state selection performance, which makes it particularly attractive for high-speed large-capacity data transmission, optical computing, and high-security photon encryption systems.
vortex beams orbital angular momentum spin angular momentum total angular momentum tailoring Advanced Photonics
2023, 5(5): 056002
强激光与粒子束
2023, 35(5): 051003