A numerical simulation of surface wave excitation in a rectangular planar-type plasma source

The principle of surface wave plasma discharge in a rectangular cavity is introduced simply based on surface plasmon polariton theory. The distribution of surface-wave electric field at the interface of the plasma-dielectric slab is investigated by using the three-dimensional finite-difference time-domain method (3D-FDTD) with different slot-antenna structures. And the experimental image of discharge with a novel slot antenna array and the simulation of the electric field with this slot antenna array are both displayed. Combined with the distribution of surface wave excitation and experimental results, the numerical simulation performed by using 3D-FDTD is shown to be a useful tool in the computer-aided antenna design for large area planar-type surface-wave plasma sources.     

Tapered dielectric structure in metal as a wavelength-selective surface plasmon polariton focuser

Symmetric tapered dielectric structures in metal have demonstrated applications such as the nanofocusing of surface plasmon polaritons, as well as the waveguiding of V-channel polaritons. Yet the fabrication of smooth-surfaced tapered structure remains an obstacle to most researchers. We have successfully developed a handy method to fabricate metal-sandwiched tapered nanostructures simply with electron beam lithography. Though these structures are slightly different from conventional symmetric V-shaped structures, systematic simulations show that similar functionality of surface plasmon polariton nanofocusing can still be achieved. When parameters are properly selected, wavelength-selective nanofocusing of surface plasmon polaritons can be obtained.     

基于DNA自组装的金属纳米结构制备及相关纳米光子学研究

纳米光子学是研究光在纳米尺度下的行为以及光和纳米材料相互作用的一门科学.金属纳米材料凭借其独特的表面等离子体效应,可以在衍射极限以下对光进行传递和聚焦,因而是纳米光子学研究的重点.大量研究表明,通过调控金属纳米材料的形貌和成分可以控制表面等离子体的性质,从而对光进行可控调节.近年来,随着DNA纳米技术的发展,又为纳米光子学的发展带来了新的机遇.首先,人们发现不同的DNA序列可以调控金属纳米颗粒的成长,从而影响金属纳米颗粒的形貌和成分.此外,利用DNA自组装技术,可以将金属纳米颗粒组装成为有序可控的纳米结构.因此,基于DNA的纳米光子学研究近年来发展十分迅速.在此背景下,本文对相关研究进行归纳与总结,以期吸引更多研究人员的关注,推动该领域的进一步发展.本文首先介绍了金属纳米结构基于表面等离体实现突破光学衍射极限的原理,然后按照DNA对金属纳米结构的形貌或成分影响方式的不同分成若干部分,对基于DNA的纳米光子学做了系统的综述,最后展望了未来可能的发展方向.     

A subwavelength metal-grating assisted sensor of Kretschmann style for investigating the sample with high refractive index

In this paper, a subwavelength metal-grating assisted sensor of Kretschmann style that is capable of detecting the sample with a refractive index higher than that of the substrate is proposed. The sensor configuration is similar to the traditional Kretschmann structure, but the metal film is pattered into a grating. As a TM-polarized laser beam impinges from the substrate, a resonant dip point in reflectance curve is produced at a certain incident angle. Our studies indicate that the sensing sensitivity and resolution are affected by the grating's gap and period, and after these parameters have been optimized, a sensing sensitivity of 51.484°/RIU is obtained with a slightly changing resolution.     

Research of photolithography technology based on surface plasmon

This paper demonstrates a new process of the photolithography technology,used to fabricate simply fine patterns,by employing surface plasmon character.The sub-wavelength periodic silica structures with uniform silver film are used as the exposure mask.According to the traditional semiconductor process,the grating structures are fabricated at exposing wavelength of 436 nm.At the same time,it provides additional and quantitative support of this technique based on the finite-difference time-domain method.The results of the research show that surface plasmon characteristics of metals can be used to increase the optical field energy distribution differences through the silica structures with silver film,which directly impact on the exposure of following photosensitive layer in different regions.     

亚波长周期性各向异性金属薄膜的等离子体共振特性

 基于各向异性模型,运用全矢量的3维时域有限差分法（FDTD）,研究了在外磁场作用下,亚波长周期性各向异性金属薄膜的表面等离子体共振机制和特性,即由周期性穿孔形成的局域波导共振和由周期性结构引起的光子晶体共振效应。研究发现:当薄膜厚度一定时,两种等离子体共振模式都会随着外磁场的增大而向短波方向移动;而当外磁场一定、薄膜变厚时,周期结构因素引起的共振传输峰向长波方向转移,波导共振传输峰向短波方向转移;通过调控外加磁场的大小或方向可控制光通过金属薄膜的增强传输效应。     

基于表面波的新型光子晶体分束器

通过激发光子晶体-光子晶体表面波的方法,设计出了一种由表面修饰光子晶体组成的新型复合结构。利用平面波展开法结合超原胞技术对该结构的耦合表面波色散关系进行了研究,在此基础上利用时域有限差分法对光束在该结构中的传输特性进行了数值模拟,并分析了其物理机制。研究结果表明,所提出的新型结构,对一定频率范围内的传输光,能够实现输出光的分束,此特征可以用来制作光束分束器。     

装置参数对狭缝天线激发的等离子体表面波传播的影响

采用时域有限差分法对矩形结构装置的等离子体表面波传播进行了三维数值模拟.研究了装置参数(如介质板相对介电常数、厚度以及介质板上方空气间隙)对天线阵列激发的等离子体表面波传播的影响,给出了合适的介质板相对介电常数和厚度,并指出空气间隙的存在会严重削弱天线阵列对表面波的激发.计算结果可为大面积矩形表面波等离子体源装置的优化设计提供参考. 关键词： 时域有限差分法 等离子体表面波 狭缝天线     

Optical bistability of planar metal/dielectric nonlinear nanostructures

We study theoretically a nonlinear response of the planar metal/dielectric nanostructures constituted from periodical array of ultra thin silver layers and the layers of Kerr-like nonlinear dielectric. We predict hysteresis-type dependences of the components of the tensor of effective dielectric permittivity on the field intensity allowing the change in material transmission properties from transparent to opaque and back at extremely low intensities of the light. It makes possible to control the light by light in all-optical nanoscale devices and circuits.     

数值模拟探针诱导表面等离子体共振耦合纳米光刻

采用有损耗介质和色散介质的二维时域有限差分方法,数值模拟了以光波长514.5nm的p偏振基模高斯光束为入射光源,激发Kretschmann型表面等离子体共振,并通过探针的局域场增强效应实现纳米光刻的新方法——探针诱导表面等离子体共振耦合纳米光刻.分别就探针与记录层的间距以及探针针尖大小,模拟分析了不同情况下探针的局域场增强效应和记录层表面的相对电场强度振幅分布.结果表明,探针工作在接触模式时,探针的局域场增强效应最明显,记录层表面的相对电场强度振幅的对比度最大;当探针针尖距记录层5nm时,针尖下方记录层表面的相对电场强度振幅大于光刻临界值的分布宽度与针尖尺寸相近. 关键词： 纳米光刻 表面等离子体共振 时域有限差分方法     

周期排列的电介质小球所诱发的金属-电介质表面上的表面等离子激元的光学性质

研究了金属板的上下表面附近各放置一层按周期排列的电介质小球的体系的光学性质.用多重散射法计算的结果显示金属上侧的周期性排列的电介质小球可诱发金属-电介质表面上的表面等离子激元.这些表面等离子激元的存在可通过非常尖锐的吸收峰反映出来.对于无限厚的金属板，这些吸收峰的峰值位置主要与电介质小球的周期有关，且与解析理论符合得相当好.在有限厚度的金属板中，金属板的两侧表面会产生对称和反对称的两种表面等离子激元，从而使原来在无限厚的金属表面上所出现的单一频率的表面等离子激元劈裂为双频率.由于对称和反对称的表面等离子激元模式在金属板的两侧表面均有相当强的电磁场，因而它们可导致强的电磁波穿透.通过在金属板的下侧加入玻璃球层可将表面等离子激元的电磁场引导出金属，并产生透射波.用多重散射法计算的结果证实，在此体系中由表面等离子激元所引起的透射可达到相当的强度. 对该体系中的物理机理进行了详细分析，从而能够通过调节该体系中的一些参数来控制表面等离子激元出现的频率，使强吸收峰或强透射峰出现在所希望的频率上. 关键词： 表面等离子激元 吸收谱 透射     

Propagation of THz plasmon pulse on corrugated and flat metal surface

We report here experiments on surface plasmon excitation and propagation along corrugated and smooth aluminum surface in the terahertz frequency range. Narrowband plasmon excitation by a subpicosecond terahertz pulse is shown to be a transient process and plasmon propagation sufficiently changes its measured time profile. Plasmon propagation during its excitation and detection changes measured signal. We suggest to use parameters T (plasmon duration) and τ (plasmon lifetime) to describe the narrowband THz plasmon pulse. Plasmon duration and lifetime were defined and plasmon propagation lengths on smooth and corrugated surface were measured. Plasmon propagation length on flat surface turned out to be much smaller than it is predicted by the Drude model.     

太赫兹波段下金属狭缝的透射增强特性研究

用太赫兹时域光谱技术研究了具有不同宽度的金属狭缝透射光谱特征. 实验结果显示在实验测量有效光谱范围(02 THz—26 THz)内,当狭缝宽度小到一定程度,在频谱中出现了共振增强,具有明显的带通带阻现象,并在理论上分析了这种共振透射现象的原因. 关键词： 表面等离子体 太赫兹脉冲 时域光谱技术 金属狭缝     

含有凹口的金属纳米环形共振器的本征模式分裂

提出了一种含有凹口金属纳米环形共振器结构,采用时域有限差分方法模拟了表面等离子体在这种结构中的传播特性.详细研究了凹口的长度、位置以及环的半径对透射性质的影响,发现当凹口的长度满足一定条件,并且处于某些特定位置的时候,与没有凹口的环形共振器相比,本征透射模式会发生分裂.随着环半径的增加,透射模式会向长波长方向移动,但不会对模式的分裂造成影响.     

表面等离子体环形共振器的滤波性质

利用时域有限差分法研究了基于金属-绝缘体-金属结构的环形波导共振器的滤波特性.研究结果表明,环形波导中存在多个共振模式.共振波长受环形波导的内径调制,随着环形波导内径的增加共振波长发生红移.共振带宽受耦合距离调制,随着耦合距离的增加带宽显著地减小.     

表面纳米结构的自组装生长

无论是对低维基本物理以及其中新奇量子现象的探索与认识,还是微电子工业水平的持续发展,都迫切地需要掌握一种能够精确、可靠地操控表面纳米结构的方法.自组织生长,即粒子聚集时由于介观尺度力场或受限运动作用而导致的自发有序现象,在原子尺度上可以实现对纳米结构的精确控制,而在介观尺度上又可以调节这些微观结构单元的组织构型.文章结合作者近年来在表面纳米结构生长与物理性质研究方面所做过的工作,从自组织生长的原理出发,介绍了对金属纳米线、有序分子薄膜以及合金量子点阵列生长进行人工操控的方法.     

基于类表面等离子体激元的矩形金属光栅色散特性的研究

等离子体激元(surface plasmon polaritons, SPP)因其独特的光学和物理特性, 使其具有诸如透射增强和局域共振等一系列新颖现象, 已成为当前国内外学者研究的热点. 本文对基于类表面等离子体激元(Spoof Surface Plasmons, SSP)的矩形金属光栅色散特性和模式分布进行了研究. 利用本征函数法并结合场匹配条件, 获得了矩形栅表面SSP的场表达式、色散关系和模式分布, 并通过电磁仿真进行了验证. 在此基础上分析了矩形栅各参数对SSP色散及模式分布的影响, 研究结果表明: 由本征函数法获得的SSP色散特性与仿真结果基本符合; 增大金属栅高度或减小排列周期能减小SSP的相速度; 而增大金属栅周期占空比能在一定程度上拓展SSP与电子束互作用的带宽; 改变金属盖板高度对慢波SSP色散模式基本没有影响; 减小金属栅侧面宽度能增大模式之间的间隔, 从而能有效避免模式竞争的发生. 本文对基于SSP的矩形金属光栅色散特性的研究将为进一步研究SSP与电子束的相互作用, 形成高效、宽带的新型太赫兹源奠定良好的理论基础.     

Effects of a one-dimensional surface defect on designer surface plasmon polaritons

By using a finite difference time domain(FDTD) method,the effects of a one-dimensional(1D) surface defect on designer surface plasmon polaritons(designer SPPs) supported by a 1D metallic grating in THz domain are investigated.When the size of the defect is in a special range which is not too large,the designer SPPs reflected and scattered by the defect are weak enough to be neglected.The defect only induces a disturbance in the energy distribution of the designer SPP supported by the whole defect grating.If the defect size exceeds the said range,the reflecting and scattering are dominant in the influences of the defect on designer SPPs.Our analysis opens opportunities to control and direct designer SPPs by introducing a 1D defect,especially in low frequency domain.     

Enhanced light absorption of silicon in the near-infrared band by designed gold nanostructures

A scheme to enhance near-infrared band absorption of a Si nanoparticle by placing the Si nanoparticle into a designed gold nanostructure is proposed. Three-dimensional （3D） finite-difference time-domain simulations are employed to calcu- late the absorption spectrum of the Si nanostructure and maximize it by generating alternate designs. The results show that in the near-infrared region over 700 nm, the absorption of a pure Si nanoparticle is very low, but when the same nanoparticle is placed within an optimally designed gold nanostructure, its absorption cross section can be enhanced by more than two orders of magnitude in the near-infrared band.     

基于FDTD方法的光栅结构光谱特性研究

基于时域有限差分(FDTD)法,从麦克斯韦方程组出发,结合周期边界条件将完全匹配层SAC-PML吸收边界条件应用到所建立的光栅数值模型中.对光栅结构和光滑表面结构的光谱特性进行了数值计算,得到了TM波入射时结构的吸收率,讨论了金属光栅耦合的表面等离子极化(SPPs)和空腔谐振模(Microcavity Mode)现象....