可电调谐超材料研究

超材料的谐振特性与其周期单元特性相关,周期单元的某一或是某几个参数的改变可以实现对超材料反射特性的调谐。利用有源集总元件的可变电阻特性,结合超材料设计,通过仿真优化和实验制备得到可电调谐超材料;分析对比了两种不同的布线方式所带来的不同的反射率特性和可调谐特性;并采用等效电路法对主动FSS层的阻抗特性进行了分析。     

基于硫属化物相变材料的可重构太赫兹超表面器件的研究进展

超表面在控制电磁波的强度、相位、偏振和复杂波前等方面发挥了重要的作用,通过与各种主动调控手段结合可实现动态可调谐器件。本文分析总结了近期基于Ge₂Sb₂Te₅ (GST)的太赫兹超表面器件的研究进展,介绍了GST在太赫兹波段的光谱特性和可逆相变条件,重点回顾了GST与超表面设计相结合用于实现对太赫兹波的振幅、偏振以及波前的非易失、可重构、和多级操纵的前沿研究工作,并讨论展望了未来的发展前景和需要解决的问题。

     

基于相变材料GST的圆二色性可调谐外在手征超表面设计

本文提出了一种基于相变材料Ge₂Sb₂Te₅ (GST)的圆二色性可调谐外在手征超表面,该超表面由两层对称的银(Ag)方形开口谐振环和GST中间层单元周期排列而成。结合斜入射光线,该超表面能实现与手征结构相同的电磁特性。数值模拟结果表明：该超表面在50 THz～300 THz的频率范围内,GST为非晶态时,圆二色性(CD)值最大为0.85;GST为晶态时,CD值最大为0.52。当GST在两种相态(非晶态-晶态)之间切换时,实现了70 THz左右的频率调谐。通过研究电场分布,解释了圆二色性产生的原因;还研究了入射角和结构参数对该超表面圆二色性的影响。这项研究在光频段高效偏振调制器件、圆偏振器和偏振滤光器等方面有潜在的应用价值。     

可调谐手征超表面电磁特性研究进展

手征超表面是由具有特定电磁响应的平面手征单元结构构成的超薄超材料,由于其具有自由控制电磁波的奇异能力而引起了极大的关注.通过在超表面设计中加入可调谐材料,可以实现其功能受外部激发控制的可调谐或可重构的超器件,为动态调谐电磁波开辟了新的道路.本文介绍了可调/可重构手征超表面电磁特性的一些理论基础,当线偏振光进入可调谐手征...     

动态可调谐超表面的研究进展与应用

超表面能够对电磁波的偏振、振幅和相位等物理参量进行前所未有的调控,微纳加工技术的发展进一步推动了超表面在显示、成像、传感、防伪、光场调控等领域的应用前景。然而,大多数超表面缺乏动态调控,限制了其应用范围。近年来超表面的动态调控研究也取得了一些重要进展,本文将主要介绍当前超表面动态调控的主要机制,包括电调控、热调控、光调控、机械调控、化学调控等,综述了国内外学者在超表面动态调控方面的研究进展。此外,本文还对动态超表面在成像、显示、光场调控等领域的应用进行了概述,阐述了其重要意义和应用前景。最后本文总结了当前可调超表面的主要问题及未来发展方向。

     

新型全介质谐振表面二元超材料吸波体

基于干涉理论,利用低介电材料全介质谐振表面(All-dielectric resonance surface,ADRS)设计并制备了一种新型二元结构超材料吸波体(Binary-structural metamaterial absorber,BMA)。优化后的BMA分别在13. 332 GHz、16. 722 GHz和17. 34 GHz处有强吸收。通过阻抗分析、能量损耗分布及场分析的方法解释了BMA的谐振与吸波机理,并研究了ADRS结构参数对吸波性能的影响。分析表明,BMA的三频谐振来源于ADRS的电谐振响应; ADRS的结构决定谐振峰处磁场分布,进而影响吸波性能。仿真结果与实测结果吻合较好。本工作提出的采用低介电材料ADRS代替传统金属谐振表面及难以制备的高介电常数ADRS,极大地简化了超材料吸波体的设计。     

基于介质超表面的径向偏振贝塞尔透镜

本文提出了一种基于介质超表面的径向偏振贝塞尔透镜,它可以高效率地将线偏光转换为径向偏振光,并且同时实现贝塞尔聚焦。在线偏振光入射下,利用非对称光子自旋轨道相互作用对线偏振光左右旋分量进行独立调控,最后通过自旋重组同时实现偏振转换和波前调控。在波长为532 nm处,数值孔径NA=0.9,超透镜实现了超越衍射极限聚焦焦斑。该项研究在粒子加速和超分辨率成像方面具有潜在的应用价值。     

吸波超材料研究进展

吸波超材料由于其独特的电磁特性,在过去十几年内成为吸波功能材料领域的研究热点.本文通过对近些年吸波超材料报道的归纳总结,对吸波超材料的研究进展进行介绍.经过多年来的发展,吸波超材料从最初的单一功能窄频段吸波特性逐渐向宽频带、宽角度入射、可智能调节等多功能方向发展,而在吸波频段的研究也由微波频段扩展至太赫兹、近红外、可见...     

超介质电磁隐身斗篷的研究进展

超介质(Metamaterials)是近年迅速发展起来的能够获得任意介电常数和磁导率进而调控电磁波传播的新颖介质.介绍了基于坐标变换的电磁隐身斗篷的基本理论,综述了超介质电磁隐身斗篷的研究进展,包括“封闭式”隐身斗篷、外隐身斗篷、隐身地毯等几种不同的隐身斗篷,这些隐身斗篷都具有良好的隐身效果,在隐身技术方面,尤其是在军事方面具有非常重要的应用价值.     

Reversible Image Contrast Manipulation with Thermally Tunable Dielectric Metasurfaces

Increasing demand for higher resolution of miniaturized displays requires techniques achieving high contrast tunability of the images. Employing metasurfaces for image contrast manipulation is a new and rapidly growing field of research aiming to address this need. Here, a new technique to achieve image tuning in a reversible fashion is demonstrated by dielectric metasurfaces composed of subwavelength resonators. It is demonstrated that by controlling the temperature of a metasurface the encoded transmission pattern can be tuned. To this end, two sets of nanoresonators composed of nonconcentric silicon disks with a hole that exhibit spectrally sharp Fano resonances and forming a Yin‐Yang pattern are designed and fabricated. Through exploitation of the thermo‐optical properties of silicon, full control of the contrast of the Yin‐Yang image is demonstrated by altering the metasurface temperature by ΔT ≈ 100 °C. This is the first demonstrated technique to control an image contrast by temperature. Importantly, the turning technique does not require manipulating the external stimulus, such as polarization or angle of the illumination and/or the refractive index of this environment. These results open many opportunities for transparent displays, optical switches, and tunable illumination systems.     

Phototunable Dielectric Huygens' Metasurfaces

Conventional dielectric metasurfaces achieve their properties through geometrical tuning and consequently are static. Although some unique properties are demonstrated, the usefulness for realistic applications is thus inherently limited. Here, control of the resonant eigenmodes supported by Huygens' metasurface (HMS) absorbers through optical excitation is proposed and demonstrated. An intensity transmission modulation depth of 99.93% is demonstrated at 1.03 THz, with an associated phase change of greater than π/2 rad. Coupled mode theory and S‐parameter simulations are used to elucidate the mechanism underlying the dynamics of the metasurface and it is found that the tuning is primarily governed by modification of the magnetic dipole‐like odd eigenmode, which both lifts the degeneracy, and eliminates critical coupling. The dynamic HMS demonstrates wide tunability and versatility which is not limited to the spectral range demonstrated, offering a new path for reconfigurable metasurface applications.     

Tunable Fano-Resonant Metasurfaces on a Disposable Plastic-Template for Multimodal and Multiplex Biosensing

Metasurfaces are engineered nanostructured interfaces that extend the photonic behavior of natural materials, and they spur many breakthroughs in multiple fields, including quantum optics, optoelectronics, and biosensing. Recent advances in metasurface nanofabrication enable precise manipulation of light–matter interactions at subwavelength scales. However, current fabrication methods are costly and time-consuming and have a small active area with low reproducibility due to limitations in lithography, where sensing nanosized rare biotargets requires a wide active surface area for efficient binding and detection. Here, a plastic-templated tunable metasurface with a large active area and periodic metal–dielectric layers to excite plasmonic Fano resonance transitions providing multimodal and multiplex sensing of small biotargets, such as proteins and viruses, is introduced. The tunable Fano resonance feature of the metasurface is enabled via chemical etching steps to manage nanoperiodicity of the plastic template decorated with plasmonic layers and surrounding dielectric medium. This metasurface integrated with microfluidics further enhances the light–matter interactions over a wide sensing area, extending data collection from 3D to 4D by tracking real-time biomolecular binding events. Overall, this work resolves cost- and complexity-related large-scale fabrication challenges and improves multilayer sensitivity of detection in biosensing applications.     

聚合物基复合介电材料的研究进展

聚合物基复合介电材料是以有机聚合物为基体,将具有高介电常数或易极化的微纳米尺寸的无机颗粒或其它有机物作为填充物复合而成,综合了无机材料的高介电性能,同时还兼备聚合物的粘结性、韧性、易加工性,在信息和微电子工业等领域具有广泛应用.该领域的研究与应用的关键是材料合成路线的设计与性能的有机结合,聚合物基体与表面修饰无机颗粒界面的良好作用,使其具有优良的介电特性.将聚合物基复合介电材料的填料颗粒分为铁电陶瓷、氧化物、碳纳米管类、金属导电颗粒、全有机高分子等几种类型,并概述了各种类型的聚合物基复合介电材料的研究状况,着重分析了聚合物与无机颗粒界面的相互作用,展望了聚合物基复合介电材料未来的发展趋势.     

低介电常数微波介质陶瓷研究进展

随着微波通信技术向毫米波段延伸,低介电常数微波介质陶瓷的开发成为介质材料的研究热点。概述了Al2O3系、硅酸盐系、AAl2O4系(A=Zn、Mg)、钨酸盐系、磷酸盐系及石榴石结构化合物体系等低介电常数微波陶瓷材料体系的研究进展,并指出了低介电常数微波介质陶瓷目前存在的问题及发展趋势。     

具有光学活性高性能高分子材料的研究进展

旋光性聚合物可以使通过它的偏振光发生偏转,在手性识别和对映体拆分、手性催化剂、液晶、生物医药、光学开关和非线性光学等领域展现出良好的应用前景。本文综述了几种利用旋光性单体缩聚合成具有光学活性高分子材料的方法,对所得聚合物的热稳定性、可溶性、旋光性等主要性能进行分析比较,得到一系列重要的结论,并对其影响机理进行讨论。在此...     

Spatiotemporal Dielectric Metasurfaces for Unidirectional Propagation and Reconfigurable Steering of Terahertz Beams

Next-generation devices for low-latency and seamless communication are envisioned to revolutionize information processing, which would directly impact human lives, technologies, and societies. The ever-increasing demand for wireless data traffic can be fulfilled by the terahertz band, which has received tremendous attention as the final frontier of the radio spectrum. However, attenuation due to atmospheric humidity and free-space path loss significantly limits terahertz signal propagation. High-gain antennas with directional radiation and reconfigurable beam steering are indispensable for loss compensation and terahertz signal processing, which are associated with spatial and temporal dimensions, respectively. Here, experimental demonstration of a spatiotemporal dielectric metasurface for unidirectional propagation and ultrafast spatial beam steering of terahertz waves is shown. The spatial dimension of the metasurface provides a solution to eliminate backscattering of collimated unidirectional propagation of the terahertz wave with steerable directionality. Temporal modulation of the spatial optical properties enables ultrafast reconfigurable beam steering. Silicon-based spatiotemporal devices amalgamate the rich physics of metasurfaces and technologies that are promising for overcoming the bottlenecks of future terahertz communication, such as high-speed and secure wireless data transmission, beamforming and ultrafast data processing.     

微波烧结微波介质陶瓷的研究进展

随着通信行业的发展,尤其是5G商用时代的来临,微波介质陶瓷的开发与探索成了近年来的研究热点.目前通常采用常压固相烧结的方式来制备微波介质陶瓷,但烧结温度较高、加热速度慢,且烧结时间过长,不仅会导致资源的损耗,还可能导致晶粒的异常长大.为了降低陶瓷材料的烧结温度,通常会添加烧结助剂,如B2 O3、CuO等,但加入烧结助剂会引入第二相从而影响微波介电性能.作为一种高效的烧结方法,微波烧结技术是在烧结过程中通过微波与材料粒子的相互作用或微波与基本微观结构耦合产生的热量进行加热,不仅能降低烧结温度、缩短烧结时间,还能改善材料的显微组织,因此,近年来微波烧结成为研究者关注的焦点.采用微波烧结制备的微波介质陶瓷在各个领域中都有应用,如Mg2 TiO4陶瓷用于多层电容器和微波谐振器,BaTiO3陶瓷用于多层陶瓷电容器(MLCC)和随机存取存储器(RAM),MgTiO3陶瓷用于微波滤波器、通信天线和微波频率全球定位系统,TiO2陶瓷用于电容器和低温共烧陶瓷基板等.不仅如此,采用微波烧结制备的微波介质陶瓷还表现出优异的化学稳定性和力学性能,如LiAlSiO4基陶瓷、MgO-B2 O3-SiO2基陶瓷等在多层陶瓷基板与微波集成电路中都有广泛的应用.微波烧结技术为制备优异的材料提供了可能,还可用于在各种粉末的制备,实现性能的进一步提升.本文综述了微波烧结制备微波介质陶瓷的研究进展,总结了常规烧结和微波烧结对材料性能的影响,并指出采用微波烧结制备的微波介质陶瓷目前存在的问题与发展趋势.     

介电温度稳定型钛酸钡基陶瓷的研究进展

综述了介电温度稳定型钛酸钡基陶瓷的研究进展.概述了钛酸钡粉体的常用制备方法、改善介电温度稳定性的主要方法,以及低温烧结钛酸钡基陶瓷的研究现状.最后展望了介电温度稳定型钛酸钡基陶瓷的发展趋势和研究方向.