基于圆微带天线阵的射频涡旋电磁波的产生

射频涡旋电磁波等相位面呈涡旋状,是一种携有新自由度-轨道角动量的电磁波。在轨道角动量模式理论分析的基础上,提出了在中心频率6 GHz处产生携有轨道角动量的涡旋电磁波的一种圆微带天线阵新结构,设计了以双层圆形微带天线为阵元组成的圆形阵列天线,通过控制馈源的相位差,得到模式量子数为0,1,2, 3, 4的轨道角动量。仿真结果表明：携轨道角动量的电磁波矢量电场图具有涡旋波阵面的特性,合适的阵列半径和馈线排列分布将产生携有良好轨道角动量特性的涡旋电磁波,而不当的阵列半径或馈线排列分布将出现能量的分散或者相互耦合的问题。     

Design of cylindrical conformal transmitted metasurface for orbital angular momentum vortex wave generation

We propose a cylindrical conformal transmitted metasurface for orbital angular momentum vortex wave generation. Formulas for calculating the phase distributions of cylindrical conformal transmitted metasurface is presented. A prototype of the proposed conformal transmitted metasurface is designed, fabricated and measured. Measured results shows that the proposed conformal transmitted metasurface can effectively generate vortex waves, which verifies the effectiveness of our method. The proposed method may pave the way of vortex wave generation with cylindrical conformal devices.     

Ku/K波段双频涡旋电磁阵列天线设计

涡旋电磁波具有携带轨道角动量的特性,利用这一特性,采用涡旋电磁波作为信号的载体,可以实现同一时间、同一频段的多路信号传输,极大地提高系统容量和频带利用率。以同轴馈电的半圆型开槽微带天线为单元,设计出了一种能工作在Ku波段和K波段的涡旋电磁阵列天线。使用三维电磁场仿真软件建模并且优化参数,最终得到在中心频率分别为17.1 GHz和19.7 GHz时,阵列天线产生的电磁波携带有轨道角动量。结论表明：该阵列天线能够产生双频涡旋电磁波。     

基于双层超表面的宽带、高效透射型轨道角动量发生器

提出一种宽带、高传输效率的双层超表面,其单元结构是在介质层两边对称刻蚀结构参数相同的十字型金属贴片且将两层超表面沿y方向错位半个周期长度形成.通过引入y方向的错位,双层超表面的透射带宽得到大幅度提升.同时,采用等效电路理论分析了该双层超表面的带宽展宽机理.在此基础上,进一步结合Pancharatnam-Berry相位原...     

C波段携轨道角动量螺旋波微带阵天线设计

本文以同轴馈电的矩形微带天线作为阵单元,将8个相同的单元天线等间隔分布在一个同心圆面上以组成微带阵天线,并采用等幅但相邻单元间相位差为一常数的方式进行激励。基于三维高频结构电磁模拟软件仿真优化,在中心频率为6 GHz处,根据不同的相位延迟得到不同模式的携有轨道角动量的方向图。仿真结论表明,该新颖的微带阵天线能产生携有轨道角动量的螺旋电磁波。     

Digital coding transmissive metasurface for multi-OAM-beam

Orbital angular momentum (OAM) is a phenomenon of vortex phase distribution in free space, which has attracted enormous attention in theoretical research and practical application of wireless communication systems due to its characteristic of infinitely orthogonal modes. However, traditional methods generating OAM beams are bound to complex structure, large device, multiple layers, complex feed networks, and limited beams in microwave range. Here, a digital coding transmissive metasurface (DCTMS) with a single layer substrate and the bi-symmetrical arrow is proposed and designed to generate multi-OAM-beam based on Pancharatnam−Berry (PB) phase principle. The 3-bit phase response can be realized by encoding the geometric phase into rotation angle of unit cell for DCTMS. Additionally, the phase compensation of the metasurface is introduced to achieve the beam focusing and the conversion from spherical wave to plane wave. According to the digital convolution theorem, the far-field patterns and near-field distributions of multi-OAM-beam withl= −2 modes are adequately demonstrated by DCTMS prototypes. The OAM efficiency and the purity are calculated to demonstrate the excellent multi-OAM-beam. The simulated and experimental results illustrate their performance of OAM beams. The designed DCTMS has profound application in multi-platform wireless communication systems and the multi-channel imaging systems.     

单环多段光强分布检测光学涡旋拓扑荷值

针对涡旋光束检测范围局限这一问题, 提出了一种新的光学涡旋拓扑荷值检测方法-单环多段光强分布检测法, 它以分段数和环半径为两大检测常数, 将检测涡旋光束拓扑荷值范围扩大到了128种, 与以往利用旁瓣调控光学涡旋检测拓扑荷值方法相比, 检测范围扩大了1个数量级. 单环多段光强分布是基于计算机全息图实现在远场衍射焦平面上环半径相等的两束携带不同拓扑荷数的涡旋光束叠加后形成的光强分布. 计算机模拟和光学实验验证了所提出方法的可行性, 该方法在自由空间光通信领域具有一定的研究价值和应用潜力.     

Microscale vortex laser with controlled topological charge

A microscale vortex laser is a new type of coherent light source with small footprint that can directly generate vector vortex beams. However, a microscale laser with controlled topological charge, which is crucial for virtually any of its application, is still unrevealed. Here we present a microscale vortex laser with controlled topological charge. The vortex laser eigenmode was synthesized in a metamaterial engineered non-Hermitian micro-ring cavity system at exceptional point. We also show that the vortex laser cavity can operate at exceptional point stably to lase under optical pumping.The microscale vortex laser with controlled topological charge can serve as a unique and general building block for nextgeneration photonic integrated circuits and coherent vortex beam sources. The method we used here can be employed to generate lasing eigenmode with other complex functionalities.     

Geometric metasurface fork gratings for vortex‐beam generation and manipulation

In recent years, optical vortex beams possessing orbital angular momentum have received much attention due to their potential for high‐capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provide infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile solution for generating vortex beams of arbitrary orbit angular momentum. Among various types of metasurfaces, the geometric phase metasurface has shown great potential for robust control of light‐ and spin‐controlled wave propagation. Here, we realize a novel type of geometric metasurface fork grating that seamlessly combine the functionality of a metasurface phase plate for vortex‐beam generation, and that of a linear phase gradient metasurface for controlling the wave‐propagation direction. The metasurface fork grating is therefore capable of simultaneously controlling both the spin and the orbital angular momentum of light.

     

Real-time programmable coding metasurface antenna for multibeam switching and scanning

Novel electromagnetic wave modulation by programmable dynamic metasurface promotes the device design freedom, while multibeam antennas have sparked tremendous interest in wireless communications. A programmable coding antenna based on active metasurface elements (AMSEs) is proposed in this study, allowing scanning and state switching of multiple beams in real time. To obtain the planar array phase distribution in quick response, the aperture field superposition and discretization procedures are investigated. Without the need for a massive algorithm or elaborate design, this electronically controlled antenna with integrated radiation and phase-shift functions can flexibly manipulate the scattering state of multiple beams under field-programmable gate array (FPGA) control. Simulation and experimental results show that the multiple directional beams dynamically generated in the metasurface upper half space have good radiation performance, with the main lobe directions closely matching the predesigned angles. This metasurface antenna has great potential for future applications in multitarget radar, satellite navigation, and reconfigurable intelligent metasurfaces.     

声波的“漩涡”——声学轨道角动量的产生、操控与应用

具有螺旋形相位位错的声涡旋场近来受到了大量关注,因为其所携带的声学轨道角动量具有重要的理论意义与显著的应用价值。当声涡旋与物体相互作用时可以实现角动量的传递,产生可以远程局域或者旋转物体的力矩,这种力学效应对粒子操控等领域意义重大。产生声学轨道角动量的传统方法需要使用由大量独立操控的换能器组成的有源声阵列或是具有不平整厚度及螺旋形结构的无源材料,限制了其在实际中的应用潜力。为利用平面状的小尺寸器件来高效产生声学轨道角动量,发展了基于共振原理的角动量生成技术。最近,声学轨道角动量被拓展至用于开辟新的多路复用信道,以实现高容量的声学通信。文章详细介绍声学轨道角动量的产生、操控及应用方面的最新研究进展。     

Chiral nanoemitter array: A launchpad for optical vortices

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.     

X波段宽频带多模轨道角动量天线仿真与设计

轨道角动量作为一种新的、安全和高效利用频谱的传输复用方式引起了科学界的关注。基于均匀圆阵列,设计了一种工作在X波段的宽带多模轨道角动量天线。该天线由旋转排列的三角形均匀圆阵列组成,其特点是正负模式数的产生除了与馈电方式有关外,还与均匀圆阵中阵元的旋转方式相关。仿真结果表明,在X频段该天线-10 dB带宽范围为9.33~10.37 GHz,带宽达到1.04 GHz,总的效率为52%;在相同阵元数量的情况下,该天线产生的模式数多于矩形贴片天线。该天线具有馈电网络简单、带宽宽和模式数大等优点。     

Proton electromagnetic form factors at large momentum transfer

We review the current experimental and theoretical status of the proton electromagnetic form factors.     

A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna

This paper presents a novel coupled receiver-transmitter metasurface (MS) which is used to realize a high-aperture-efficiency Fabry-Perot resonator antenna. The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch. This approach makes it easier to independently control the transmission magnitude and phase. Based on this characteristic, the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm. Then, nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved. Therefore, the gain and aperture efficiency of the antenna are improved. A prototype of the optimized antenna is fabricated and measured to validate the design. The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%. A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.     

Chiral Lithography with Vortex Non-diffracted Laser for Orbital Angular Momentum Detection

Chiroptical response, demonstrating chiral interaction between optical vortex and chiral structure, plays an important role in variety of fields like optics and material science. However, the flexibility and efficiency of chiral structure fabrication are limited due to mask requirement and a point-by-point constructing strategy. In this paper, a novel chiral lithography method is proposed that utilizes optical vortex phase beam shaping to achieve chiral structure processing with high efficiency and flexibility. By programming topological charges of the vortex phase, chiral structures with adjustable appearance, rotation, and chirality can be produced using femtosecond laser single pulse exposure. Transmittance measurements of fabricated chiral structures array confirm a 66% helical dichroism that is predicted by simulation. Moreover, with the aid of convolutional neural networks (CNN), an accuracy of 98% in Orbital Angular Momentum (OAM) recognition can be achieved. This chiral lithography method provides an alternative for chiral structure fabrication and holds promise in the development of chiral optics, optical communications, and next-generation optical devices.     

Study on holographic grating diffraction for Laguerre--Gaussian beam generation

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.     

加载电磁带隙结构的平切圆锥等角螺旋天线

加载电磁带隙的平切圆锥等角螺旋（EAS-EBG)天线可以在很宽的频带范围内提高辐射增益。建立了平切等角螺旋锥体（EAS）天线的基本模型,并用HFSS对其进行了仿真。研究了一种加载电磁带隙结构的平切圆锥等角螺旋锥体天线。该天线是在保持原平切等角螺旋锥体天线外形不变的情况下,加载了小型化的电磁带隙结构,以提高增益并保持共形化。仿真结果表明:加载电磁带隙结构的模型增益在5～12 GHz带宽下可以提高1～3 dB,并且轴比特性基本不变。     

Accelerating,guiding, and sub‐wavelength trapping of neutral atoms with tailored optical vortices

Single neutral atom mechanics is controllable by focused, high‐intensity optical vortices. The intensity‐dependent, laser‐driven motion of the atom's active electrons subsumes to a net transfer of the orbital angular momentum of the light to the neutral atom. The ponderomotive force on these electrons translates so into an unbounded or a bounded radial drift of the atom depending on its initial kinetic energy, as set by the temperature. Appropriate combination of laser beams results in sub‐wavelength, dynamical radial traps for tweezing atoms controllably, an effect that can be exploited for atom guiding, structuring, and lithographic applications.

     

辐射式核电磁脉冲模拟器TEM喇叭天线

针对辐射式核电磁脉冲模拟器采用TEM喇叭天线作为辐射天线时低频辐射能力有限的问题,对板型和线型两种基本形式的TEM喇叭天线进行了分析。在采用线型TEM喇叭天线以减轻模拟器重量的基础上,在天线末端采用螺旋线结构,并增加屏蔽板回路,构造了一种新型TEM喇叭天线。结果表明：与普通线型TEM喇叭天线相比,该新型天线较大地提高了低频辐射性能,可使近场波形脉宽提高7 ns左右,峰值场强提高了1 kV/m左右;通过增大螺旋线半径和提高螺旋线密度可以提高峰值场强,增加近场波形脉宽;通过屏蔽板回路可以降低反射波纹的波峰从而改善近场波形。