A coding optimized polarization conversion metasurface in broadband and wide‐angle

In this article, a coding optimized metasurface is proposed for linear polarization conversion in broadband and wide‐angle. Using an improved coding method, the geometry of the metallic structure and the size of the unit cell are encoded with a code sequence. The code sequence is optimized by genetic algorithm, considering bandwidth, efficiency, and angular stability. In this way, a coding optimized metasurface was obtained for polarization conversion in broadband and wide‐angle. It can convert linear polarized incidence to its orthogonal polarized reflection in 8 to 18.9 GHz and 0° to 45°, with the polarization conversion ratio larger than 80%. Both simulated and measured results demonstrated the effectiveness of the proposed metasurface. Hence, our method offers an effective strategy to design high‐performance polarization conversion metasurfaces.     

宽频多模态涡旋电磁波超表面设计

针对超表面产生OAM(轨道角动量)涡旋电磁波模态单一的问题,提出了一种宽频带多波束多模态OAM波束超表面的设计方法。采用方形开口环结构,优化几何参数,通过开口尺寸的变化构建8个3-bit 数字编码单元。利用矢量叠加原理,由产生单一模态OAM波束所需的相移得到多模态涡旋波束的超表面相位分布。采用天线阵列理论可直接求得超表面的远场方向图,并与全波仿真结果进行对比。研究结果表明,利用该方法设计的超表面,能够同时生成多个OAM波束,并且每个波束的辐射方向和OAM 模态可根据实际需求进行设定。设计的超表面还具有电尺寸小、剖面低和工作频带宽等优点,在无线通信领域具有广泛的应用前景。     

一种透射型线-圆极化转换超表面的设计及应用

提出了一种单对角线开缝的方形单元构成的透射型极化旋转超表面,并将其应用于宽带圆极化微带缝隙天线的设计中。采用等效电路法分析了超表面实现线-圆极化转换的工作机制,并对天线圆极化带宽的影响因素进行了参数扫描。仿真结果表明:加载超表面使线极化微带缝隙天线产生了圆极化辐射;同时,扩展了天线的阻抗带宽。天线相对阻抗带宽达到了33.2%,3 dB轴比带宽达到了19.5%,在阻抗带宽内天线增益均高于6.8 dBi,证实了新型超表面结构具有良好的极化旋转特性。     

紫外辐射计的波长定标及不确定度分析

限于常规汞灯谱线法波长定标的局限性,构建了紫外辐射计波长定标装置,研究了紫外辐射计波长定标的物理过程和测量链,并对紫外辐射计中臭氧十二个吸收波长进行了光谱定标,通过对定标影响量的分析和计算,得到定标影响量的测量不确定度和波长定标合成标准不确定度,其中波长定标合成标准不确定度为0.026nm,同时通过光学CAD分析和实验验证紫外辐射计的光谱带宽可以达到1.0nm.应用自行构建的紫外波长定标装置较好地完成了紫外辐射计臭氧吸收谱线的定标工作,满足了臭氧反演所需的波长精度要求和光谱带宽要求.     

Flexible Plasmonic Metasurfaces with User‐Designed Patterns for Molecular Sensing and Cryptography

Flexible plasmonic metasurfaces have garnered considerable attention because the material's mechanical flexibility enables new functionalities and integrated applications. Here, by adopting low‐cost materials and simple techniques, we demonstrate a method of fabricating large flexible metasurfaces with arbitrary user‐designed iridescent patterns. These naked‐eye recognizable patterns together with their excellent plasmonic activities have yielded new functionalities and novel applications. Demonstrations include plasmonic sensing, reflective displays, developing new encryption strategies and integrated devices, etc. Moreover, the low fabrication cost (?2) would enable the practical use of the material. The metasurface can even be fashioned into an innovative, multifunctional medical ID bracelet. We believe our flexible plasmonic metafilm will inspire the fabrication of many novel applications and open up new horizons in various fields.     

基于人工电磁表面的超低剖面全介质透镜天线

利用不同厚度的亚波长介质块实现0 ~2π的相位变化,并基于惠更斯人工电磁表面原理设计了工作 于28 GHz 通信频段的全介质电磁透镜,该电磁透镜的焦距与口径比(F / D)为0. 15。通过3D 打印制备该电磁透镜, 并将其与基片集成波导(SIW)贴片天线进行集成,构造了超低剖面的宽带透镜天线。全波分析与实验测量结果显示 该电磁透镜能够将原SIW 贴片天线的增益提高7 dB 左右,而将3 dB 波束宽度减小到10°左右,同时该透镜天线系统 还具有良好的低副瓣。     

透射光谱成像技术及其在相似异物检测中的应用

由于相似异物与所处背景的外观特征及反射特性极其相近,现有的光谱反射成像检测方法具有一定的局限性。本文针对相似异物采用光谱透射成像检测方法并对其中的关键技术深入研究。该方法在透射光谱成像理论模型的基础上,建立了基于综合透射差的波长优选函数,分析了近紫外-可见-近红外连续波段中异物与背景光谱透射差随波长的变化规律,筛选了区分多个异物与背景的最佳透射波长,以此构建透射光谱成像检测系统。以棉花中的白色丝状异物作为实验对象,利用最佳波长的透射成像系统获取异物特征,采用小波变换及自适应阈值的二值化处理从背景中提取异物。实验结果表明,在透射光照系数0．83条件下,该方法对相似异物的检测率达到91％,为相似异物检测提供了一种新思路。     

Generation of vector beams based on dielectric metasurfaces

Vector beam has recently attracted many attentions due to novel properties and wide applications. Finding a method efficiently generating high quality vector beam is very important when it is used in practice. In this paper, we theoretically and experimentally demonstrate the generation of vector beams based on dielectric metasurfaces, which are fabricated by femtosecond laser writing in silica glass. Three types of linearly polarized vector beams are produced by three specially designed metasurfaces. The vector beam generator is convenient and robust due to its simple optical path. We believe that metasurfaces will be widely applied in manipulating polarization, phase, and amplitude of light as the development of fabrication technology.     

超表面在红外波段的光传输特性:偏振控制、旋光性和不对称传输

超表面(Metasurfaces,MMs)是拥有亚波长尺寸谐振单元结构的人工平面材料,其电磁特性主要由结构决定。超表面具有极强的波前控制能力。本文着重介绍了近年来纳米结构超表面在红外波段的光传输特性,包括光波偏振控制、旋光性、不对称传输等方面的理论和实验研究进展,简要介绍了制备纳米结构超表面的工艺技术。     

增强双马来酰亚胺树脂基复合材料研究

石英纤维增强双马来酰亚胺树脂复合材料具有低介电损耗、耐高温、耐湿热及良好的力学性能。本文介绍了改性双马来酰亚胺树脂的分子结构与性能,及复合材料的模压成型工艺。