五层对称人工超常材料结构的表面等离子体激元

研究了由左手材料、负介电材料、常规介电材料所构成的几种五层对称结构表面等离子体激元的特性.讨论了表面等离子体激元的存在区域、色散关系、以及p和s偏振的表面色散曲线枝,发现表面模的性质强烈依赖于系统的组成材料及其组合方式;层数越多,表面色散曲线枝也越多,处在频率通带的表面极化模态也越多;在五层结构中有p和s两种偏振的表面等离子体激元,在共振时,可导致p波和s波强透射.此外,通过使用衰减全反射方法,探讨了激发并观察表面等离子体激元的可能性.     

五层对称人工超常材料结构的表面等离子体激元

研究了由左手材料、负介电材料、常规介电材料所构成的几种五层对称结构表面等离子体激元的特性.讨论了表面等离子体激元的存在区域、色散关系、以及p和s偏振的表面色散曲线枝,发现表面模的性质强烈依赖于系统的组成材料及其组合方式|层数越多,表面色散曲线枝也越多,处在频率通带的表面极化模态也越多|在五层结构中有p和s两种偏振的表面等离子体激元,在共振时,可导致p波和s波强透射.此外,通过使用衰减全反射方法,探讨了激发并观察表面等离子体激元的可能性.     

左手材料界面处表面等离子体激元的液晶调控研究

设计由向列相液晶材料/左手材料/右手材料(LC—LHM—R)构成的三层结构界面系统,使用衰减全反射(ATR)技术,研究液晶层的温度以及厚度对三层介质表面电磁波的影响,有助于理解表面等离子激元(SPPs)激发的物理机制。基于电磁场的波动理论,以P偏振为例数值分析表面电磁波的存在区域和表面等离子激元的激发位置,并通过数值模拟的方法研究液晶温度的变化对ATR光谱吸收峰的影响规律。液晶材料组成的参量对该界面表面电磁波的影响非常显著,随着液晶温度的升高SPPs色散偏振曲线向高频方向移动,界面处ATR光谱的反射极小值随着液晶层温度的增大而变小,但其对应的频率位置无明显变化;随着液晶层厚度的减小,界面处ATR光谱中的反射极小值也下降。在不改变模型结构的前提下,可以通过液晶层温度和厚度来调控三层界面表面SPPs,利用这些特性,可为表面电磁波传感器件的设计提供一定的指导意义。     

光声方法研究表面等离子激元衰减

本文用衰减全反射(ATR)和光声(PA)方法研究表而等离子激元(surface plasmons)的衰减,分别对Ag-空气界面和CaF_2-Ag-空气界面进行衰减全反射谱和光声光谱测定.测量结果确定两种衰减方式,辐射和无辐射定量结果,并且发现表面粗糙度对衰减方式有影响.     

用双介质法测定金属薄膜的厚度和光学常数

用角度扫描衰减全反射方法(ATR),激励金属和两种介质界面处的表面等离子激元波(SPW)通过这些表面等离子激元波和介质折射率的关系同时确定了金属薄膜的厚度和光学常数.实验结果和理论分析相符.     

线性偏振光激发的错位表面等离子体激元纳米结构聚焦

利用扫描近场光学显微镜观测并分析了两种表面等离子体激元纳米结构对表面等离子体激元(SPP)的激发和聚焦现象.用线偏振光照射有半个周期相位差的环状沟槽结构与有半个周期位相差的环状狭缝结构,得到了单点的SPP聚焦.有限时域差分法的模拟结果验证了实验中观测的现象.这两种相位错位的表面等离子体激元纳米结构,突破了由于干涉导致的线偏振光不能得到单个聚焦点的限制.与采用径向偏振光激发而得到单个聚焦点的方法相比,线偏振光不需要聚焦,也不需要将光束中心对准纳米结构的几何中心即可得到单点聚焦。     

长程表面等离子体的增强效应

研究了双层金属薄膜构型中构型参数对长程表面等离子体的影响,并发现了衰减全反射激发方法下长程表面等离子体的增强效应.以特征矩阵算法为基础,通过数值计算构型的反射谱,研究构型参数的变化对反射谱的影响.发现由于衰减全反射激发方法中耦合器的存在导致的非对称特性,会使双层金属薄膜构型中的长程表面等离子体拥有本征模式特性以外的有趣特性,如长程模式得到增强而另一支受到抑制,从而使能量更为集中在希望被激发的一支.研究结果对非对称激发构型中的长程表面等离子体研究具有启发意义.     

一种石墨烯波导褶皱激发表面等离子体激元的设计

设计了褶皱石墨烯波导结构激发表面等离子体激元,通过设计周期阵列结构实现了表面等离子体激元传播损耗的补偿.理论分析了周期阵列结构的表面等离子体激元传播模型和补偿损耗的方式,结果表明褶皱衍射激发表面等离子体激元波导不仅能够激发表面等离子体激元,还能利用表面等离子体激元波矢关系实现器件参数控制,周期阵列增益全程补偿损耗的方式可以显著增加表面等离子体激元的传播距离.数值分析结果进一步表明:该结构具备了保持亚波长尺寸的强局域化优势;周期阵列增益全程补偿可以显著提高纳米腔中的电场强度,降低传输损耗;波导结构的粒子反转水平较高,自发辐射噪声的扰动较低.设计的石墨烯波导器件可以为微纳光学集成、光子传感和测量等领域提供理想的亚波长光子器件.     

金膜上亚波长小孔阵列表面等离激元颜色滤波器偏振性质

金属薄膜上制备的表面等离激元颜色滤波器具有很强的颜色可调性. 在200 nm厚的金膜上, 通过聚焦离子束刻蚀, 制备一系列周期逐渐变化的圆形、方形、矩形亚波长尺寸小孔方阵列表面等离激元颜色滤波器, 改变入射光的偏振方向, 观察其超透射滤波现象. 研究发现: 对于矩形小孔阵列, 其透射光颜色随入射光偏振方向的变化而改变; 而对于圆形、方形的小孔阵列, 其透射光颜色对入射光的偏振方向并不敏感. 分析表明, 对于金膜上刻蚀的小孔结构, 虽然结构的周期性导致的表面等离激元极化子会对透射光的颜色变化产生一定影响, 但是随小孔形状变化的局域表面等离激元共振才是影响透射光颜色的决定性因素. 如果入射光没有在小孔中激发出局域表面等离激元, 则表面等离激元极化子对透射光的影响也会消失. 根据不同形状小孔周期结构透射光颜色随入射光的偏振变化特点, 制备出了包含两种小孔形状的复合周期结构. 随着入射光偏振方向的改变, 该结构会显示出不同的颜色图案. 关键词： 表面等离激元极化子 局域表面等离激元 颜色滤波器 亚波长小孔阵列     

一种石墨烯波导褶皱激发表面等离子体激元的设计（英文）

设计了褶皱石墨烯波导结构激发表面等离子体激元,通过设计周期阵列结构实现了表面等离子体激元传播损耗的补偿.理论分析了周期阵列结构的表面等离子体激元传播模型和补偿损耗的方式,结果表明褶皱衍射激发表面等离子体激元波导不仅能够激发表面等离子体激元,还能利用表面等离子体激元波矢关系实现器件参数控制,周期阵列增益全程补偿损耗的方式可以显著增加表面等离子体激元的传播距离.数值分析结果进一步表明:该结构具备了保持亚波长尺寸的强局域化优势;周期阵列增益全程补偿可以显著提高纳米腔中的电场强度,降低传输损耗;波导结构的粒子反转水平较高,自发辐射噪声的扰动较低.设计的石墨烯波导器件可以为微纳光学集成、光子传感和测量等领域提供理想的亚波长光子器件.     

A NEW FREQUENCY SELECTIVE SURFACE COMPOSED OF LEFT-HANDED MATERIALS

The frequency selective characteristics of a new dielectric periodic structure composed of left-handed materials (LHM) are carefully studied by a method which combines the multimode network theory with the rigorous mode matching method. The variations of the frequency selective characteristics with structure parameters and dielectric loss are presented and comparisons for the frequency selective properties between RHM and LHM gratings are also shown with some explanations. Guidelines for accurate design of the LHM dielectric frequency selective surface are given. Supported by the National Natural Science Foundation of China (No. 60171037) (No. 60371010) and (No. 63531020)     

Surface plasmon polaritons of symmetric and asymmetric metamaterial slabs

The p and s-polarized surface plasmon polaritons (SPPs) of symmetric and asymmetric slabs formed arbitrarily by four types of conventional materials: dielectrics, negative dielectric permittivity materials, negative magnetic permeability materials, and left-handed materials are comprehensively analysed. The existence regions, dispersion relations, and excitation of SPPs in different frequency regions are investigated in detail. For symmetric slabs, the numbers and the frequency positions of surface polariton branches are quite different. At the same time, the pairs of the p or s-polarized SPP branches occur in the same frequency range. For asymmetric slabs, the SPP branches in mid- and high-frequency ranges are greatly different. In addition, the slab thickness has a great effect on SPPs of asymmetric and symmetric slabs. The attenuated total reflection spectra for the cases of p and s polarizations in these slabs are also calculated.     

包含左手材料的四层平板波导中的光导模

研究一个芯子层是左手材料,其他三层由传统材料构成的四层平板光波导系统,利用图解法对各种TE偏振的导波模式的解进行详细分析.研究表明,四层左手材料光波导既能支持振荡导模,也能支持表面导模,与三层左手材料光波导相比较,此四层波导的导波模式呈现一些新的特性.对于中间传统材料层存在振荡场的情形:芯子层支持振荡导模的光波导中存在基模,并且高阶振荡导模出现模式缺失的性质;芯子层支持表面导模的光波导可以支持基模和多个高阶模式,并且存在模式兼并的性质.对于中间传统材料层存在衰减场的情形,此四层波导结构可等效为三层左手材料光波导.这些新的光波导传输性质对各种光波导器件的制作有潜在的应用价值.     

Topology optimization of multilayer left-handed material based on the genetic algorithm

Owing to the special properties, left-handed materials (LHM) have important potential applications in engineering. However, in the current stage, the design of LHM is primarily based on several basic prototypes such as meta-material and transmission line structures. In the present work, the topology optimization technology is introduced to design a type of multilayer LHM. A type of one-dimensional material with periodic unit cell is studied and the topology of its microstructure is designed by using the technology of enumerative search and genetic algorithm (GA), respectively. The material is composed of metal and ferrite films, and several types of negative refraction materials are obtained numerically. These obtained materials with periodic unit cells can exhibit negative refractive index in some frequency spectrums, and the results show that the GA could achieve good designs efficiently in a larger design space.     

INVESTIGATION ON EFFECTS OF LEFT-HANDED MATERIALS ON FREQUENCY SELECTIVE CHARACTERISTICS OF DIELECTRIC PERIODIC STRUCTURES

The effects of left-handed materials (LHM) on frequency selective reflection and transmission characteristics of dielectric periodic structures are carefully investigated using a method which combines the multimode network theory with the rigorous mode matching method. In addition, the effects of LHM dielectric loss on the selective properties are also given. It has been shown that the selective behavior of periodic structures can be modified by adding LHM layers above and below the periodic layer. Supported by the National Natural Science Foundation of China (No. 60171037) (No. 60371010) and (No. 63531020)     

Surface plasmon polariton at the interface of dielectric and graphene medium using Kerr effect

We theoretically investigate the control of surface plasmon polariton(SPP) generated at the interface of dielectric and graphene medium under Kerr nonlinearity. The controlled Kerr nonlinear signal of probe light beam in a dielectric medium is used to generate SPPs at the interface of dielectric and graphene medium. The positive, negative absorption, and dispersion properties of SPPs are modified and controlled by the control and Kerr fields. A large amplification(negative absorption) is noted for SPPs under the Kerr nonlinearity. The normal/anomalous slope of dispersion and propagation length of SPPs is modified and controlled with Kerr nonlinearity. This leads to significant variation in slow and fast SPP propagation. The controlled slow and fast SPP propagation may predict significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster, and sensing technology.     

Artificial polarization anomalies from holographic gratings

An aluminum reflection grating made holographically was found to display polarization anomalies when illuminated with p-polarized light. Additional anomalies were detected for both p- and s-polarizations after the grating was coated with a layer of dielectric (410 nm of photoresist). These new anomalies have been interpreted in terms of the optical guided modes of a thin film dielectric waveguide bounded on one side by metal and on the other by vacuum.     

A wide band left handed material with high transmission

In this study, we propose guidelines to optimize the transmission and bandwidth of left handed materials (LHM) composed of two-dimensional lattice of metallic wires interleaved with double split ring resonators (SRRs). Several LHM structures are fabricated to test the proposed rules of design and operate between 7 and 14 GHz. In a first step, we show that adding extra SRR layers within each period of wire layers (i.e. interleaving the wire lattice with several SRR lattices) increases the transmittance of the material. In a second step, we demonstrate that adding extra SRR layers in a non-equidistant manner (i.e. inserting several SRR lattices shifted one another by different distances) widens the LHM frequency bandwidth. The results of experimental characterization are found to be in excellent agreement with theoretical predictions. A LHM behavior is obtained in a wide frequency band of 1 GHz around 8.2 GHz with a transmission of −1.2 dB measured at resonance. The negative refraction of the material is verified from measurements at oblique incidence.     

Negative refractive index in left-handed materials

The real part of the refractive index n(omega) of a nearly transparent and passive medium is usually taken to have only positive values. Through an analysis of a current source radiating into a 1D "left-handed" material (LHM)-where the permittivity and permeability are simultaneously less than zero-we determine the analytic structure of n(omega), demonstrating frequency regions where the sign of Re[n(omega)] must, in fact, be negative. The regime of negative index, made relevant by a recent demonstration of an effective LHM, leads to unusual electromagnetic wave propagation and merits further exploration.