Plasmonic splitter based on the metal-insulator-metal waveguide with periodic grooves

In this paper, we have proposed a plasmonic splitter which is composed of a subwavelength slit and two different metal-insulator-metal (MIM) waveguides with periodic grooves. The slit is used to excite surface plasmon polaritons (SPPs) at certain wavelengths. By setting the SPPs resonance wavelengths of the slit as the Bragg wavelengths of MIM waveguides, the SPPs of different wavelengths are able to be confined and guided in the two different MIM waveguides. The numerical results of two-dimensional finite difference time domain (2D-FDTD) demonstrate that our proposed structure is capable of splitting light into two MIM waveguides.     

Tunable plasmonic filter with circular metal–insulator– metal ring resonator containing double narrow gaps

Tunable filter based on two metal–insulator–metal (MIM) waveguides coupled to each other by a ring resonator with double narrow gaps is designed and numerically investigated by finite-difference time-domain (FDTD) simulations. The propagating modes of surface plasmon polaritons (SPPs) are studied. By introducing narrow gaps in ring resonators, the transmission in different resonance modes can be effectively adjusted by changing the gap width (g), and the transmitted peak wavelength has a nonlinear relationship with g. Another structure consisting two cascading ring resonators and regular MIM waveguide have also been proposed. The mechanism based on circular ring resonators with narrow gaps may provide a novel method for designing all-optical integrated components in optical communication and computing.     

Frequency selective metal-insulator-metal splitters for surface plasmons

The authors introduce frequency selective beam splitters for surface plasmon polaritons (SPPs) in a metal-insulator-metal (MIM) structure. In the splitters, a part of SPPs keeps propagating straight along the initial direction, while the other part is split into the arm attached at right angle. The splitting ratio can be controlled by varying the width and the electric permittivity of the dielectric layer in the MIM, and by varying the width of the attached arm.     

Effect of anisotropy on the photonic band gap and surface polaritons of a one-dimensional single-negative photonic crystal

The effect of anisotropy on the photonic band structure and surface polaritons of a one-dimensional photonic crystal made of uniaxially anisotropic epsilon-negative (ε<0,μ>0) and mu-negative (ε>0,μ<0) metamaterials is theoretically investigated. Two different cases of uniaxially anisotropic epsilon-negative and mu-negative metamaterials are considered. It is found out that for one case of anisotropy, one-dimensional photonic crystal does not have any single-negative band gap. As a result, it can not support the surface polaritons. While, for another case, the structure shows single-negative band gaps. So, the surface polaritons can be excited at the interface of such a photonic crystal. However, these surface polaritons, unlike the isotropic case, are not omnidirectional and they are restricted to a limited rang of the propagation constant.     

Analysis of the plasmonic power splitter and MUX/DEMUX suitable for photonic integrated circuits

In this paper, the metal-insulator-metal (MIM) plasmonic directional coupler (PDC) with 45° waveguide bends based on surface plasmon polaritons (SPPs) excitation has been analyzed by the finite-difference time-domain (FDTD) numerical method. Effects of the variations of the coupler length and the metal gap thickness on the output powers and the propagation loss at 1550 nm wavelength have been studied. By choosing proper coupler lengths, power splitters with various output power ratios at 1550 nm wavelength and multi/demultiplexers, as some applications of the directional couplers have been proposed and their performances have been simulated.     

Gap surface plasmon polaritons enhanced by a plasmonic lens

We numerically investigate the optical field enhancement based on gap surface plasmon polaritons (GSPPs) that are enhanced by propagating surface waves launched by a circular slit at a metal-dielectric interface. The optical field enhancement originates not only from multiple scattering and coupling of GSPPs in the spacer region between two metal layers but also from propagating surface plasmon polaritons (SPPs) launched by a circular plasmonic lens. We find that the combination of the GSPPs and the propagating SPPs launched by the plasmonic lens can achieve extremely strong field confinement, and we find that the surface-enhanced Raman scattering (SERS) enhancement factor can be up to 10(15) at the tip of the equilateral triangular nanostructures. The structure proposed here is expected to find promising applications where strong field enhancement is desired, such as optical sensing with the SERS effect.     

Trapping of surface plasmon polaritons in a multiple-teeth-shaped waveguide at visible wavelengths

We numerically and theoretically demonstrate that a metal–insulator–metal (MIM) waveguide with multiple-teeth-shaped graded depths can strongly slow light as the propagation velocities of surface plasmon polaritons (SPPs) are reduced over a large frequency bandwidth at visible wavelengths domain. Since the wavelength of the trough of transmission is dependent on the depth of the tooth-shaped dielectric in the MIM waveguide, the guided SPPs at different frequencies can be localized at different spatial positions of the multiple-teeth-shaped graded depths MIM waveguide, which can be proved by the scattering matrix method. The separation between trapped waves can be tuned by changing the grade of the tooth-shaped depths and the lifetime of SPPs in the waveguide may be long enough for some meaningful nano-photonic applications.     

Active modulation of plasmonic signal with a subwavelength metal/nonlinear dielectric material/metal structure

<正>Light propagation through a metal/nonlinear dielectric material/metal(M-NL-M) structure is numerically studied.The design parameters of the M-NL-M structure are found with the waveguide theory so that the structure only supports the symmetric surface plasmon polaritons(SPP(0)) mode and the antisymmetric surface plasmon polaritons(SPP(1)) mode.The coupling between the two modes within the M-NL-M structure is exploited.Through controlling the propagation constants of the two modes with the intensity-dependent dielectric constant of the nonlinear Kerr material,an effective all-optical control of plasmonic signal modulator can be realized with this M-NL-M structure.     

Tamm plasmon polaritons in composite structures composed of the metal film and truncated photonic crystals

Tamm plasmon polaritons (TPPs) are studied theoretically and experimentally in heterostructures and sandwiched structures with the metallic film and truncated photonic crystals. Different from conventional surface plasmon polaritons, TPPs can be realized in both the transverse electric (TE) and transverse magnetic (TM) polarizations, and they can be excited from a free space. Because of nonreciprocal electromagnetic field distributions of TPPs, the structures possess strongly nonreciprocal absorption and reflection. Moreover, two tunneling peaks or a narrow transmission band can be realized in sandwiched structures for both polarizations due to the coupling effect between two TPPs.     

The optical transmission characteristics through coupled metallic nanotube arrays

The plasmonic properties in coupled metallic nanotube arrays are investigated theoretically by the finite-difference time-domain (FDTD) method. We calculate the transmission spectra and the electric field distributions. We show that there is a photonic band gap over a wide optical wavelength range and the transmission spectrum depends strongly on the inner radii, the separation distance and the number of the nanotubes. Based on the localized nature of the field distribution, we also clearly show that the presence of local plasmon resonant modes that originate from multipolar plasmon polaritons and a big magnitude of opposing surface charges build up in the gap between adjacent nanotubes.     

Waveguiding in surface plasmon polariton band gap structures

Using near-field optical microscopy, we investigate propagation and scattering of surface plasmon polaritons (SPP's) excited in the wavelength range of 780-820 nm at nanostructured gold-film surfaces with areas of 200-nm-wide scatterers arranged in a 400-nm-period triangular lattice containing line defects. We observe the SPP reflection by such an area and SPP guiding along line defects at 782 nm, as well as significant deterioration of these effects is 815 nm, thereby directly demonstrating the SPP band gap effect and showing first examples of SPP channel waveguides in surface band gap structures.     

微波频段表面等离子激元波导滤波器的实验研究

基于理论分析, 实验研究了二维磁单负材料/双正材料/磁单负材料表面等离子波导的滤波效应. 研究表明, 该波导结构具有低通滤波性质, 引入分支缺陷之后, 由于谐振效应该波导具有带阻滤波效应. 分支缺陷相当于亚波长谐振腔, 谐振腔的长度决定带阻滤波器的中心频率, 而中心频率几乎不受缺陷位置的影响; 滤波器透射率下降的幅度由耦合距离决定. 通过引入谐振腔及改变谐振腔的长度、数量以及耦合间距等参数, 可以实现可调节的表面等离子波导滤波器. 实验结果与理论分析符合得很好, 该性质将在可调的单通道或多通道带阻滤波器件中具有潜在的应用价值. 关键词： 表面等离子激元 特异材料波导 谐振腔 滤波器     

等离子体辅助平板波导的传输特性及应用研究

如何灵活地控制和操纵太赫波是目前研究的热点. 根据电磁波传输理论, 导出了等离子体辅助平板波导的场分布和色散关系表达式, 计算了其传输特性, 并通过全波仿真进行了证实. 结果表明, 等离子体辅助平板波导具有带阻特性, 上边带截止频率等于等离子体频率, 等离子体层越薄, 下边带截止频率越高, 带宽越窄; 阻带内存在两种不同的物理机理, 一种与等离子体和中间媒质的谐振耦合有关, 另一种与表面波的形成有关. 此外, 本文还研究了等离子体频率及碰撞频率对传输特性的影响, 提出了通过改变等离子体频率调谐平板波导滤波器特性的方法. 同时, 采用褶皱金属结构实现了等离子体层, 设计了平板波导传感模型, 通过改变凹槽内的材料的介电常数仿真了其传感特性, 结果表明当材料的介电常数变化0.1%时, 平均截止频率变化1.8 GHz; 通过检测截止频率的变化, 传感器能明显分辨氮、汽油、液态石蜡、甘油和水, 证实了其优良的太赫传感特性. 这项工作对研究太赫波的传输及太赫器件的设计和制备具有指导意义.     

Unidirectional manipulation of surface plasmon polariton by dual-nanocavity in a T-shaped waveguide

A structure of two dimensional T-shaped metal-insulator-metal waveguide with dual-nanocavity is proposed. The two nanocavities located at each side of the slit on the lower metallic surface, act as band rejection filters and are capable of stopping the surface plasmon polaritons (SPPs) at the resonant wavelengths. The Fabry-Perot interferometry theory and the Finite-Difference-Time-Domain method are utilized to investigate the proposed waveguide. The numerical results demonstrate the realization of miniaturized photonic devices for effectively switching the SPPs propagation between the left and right waveguides in one direction.     

Otto结构加载MIM波导的表面等离子激元传输与衰减特性

设计了加载MIM波导的Otto结构研究SPPs的传输和衰减特性,应用球面EM场的解法求解了整个介质区域的本征函数的特征值。对SiO₂厚度分别为750 nm和1 500 nm的设计结构进行了仿真,结果表明:750 nm改进结构的TM₀传播常数达到了1.541,衰减系数仅仅为2.80;随着SiO₂层介质厚度的减小,反射系数随之增大,且不同金属介电常数的谐振方向变化趋势一致;随着腔厚度的减小,在反射相位减少的同时其存储能量也随之减少。     

Photonic bandgap structures for long-range surface plasmon polaritons

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of 20 nm centered at 1550 nm. The possibilities of achieving a full bandgap (in the surface plane) for LR-SPPs are also discussed.     

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.     

基于厚金属狭缝阵列的表面等离子激元光刻

提出一种利用厚金属狭缝阵列耦合激发表面等离子激元制作非周期图形的纳米光刻模型.采用时域有限差分电磁场模拟仿真软件研究了厚金属狭缝阵列中表面等离子激元的激发、模式选择以及光刻胶中的光场分布.结果表明,通过优化厚金属狭缝阵列结构参量和匹配介质参量可有效抑制表面等离子激元在光栅狭缝出口处的发散,增加表面等离子激元的穿透深度,...     

Surface Plasmon Polaritons of Two-Dimensional Three-Order Dendritic Structures

We study surface plasmon polaritons excited on two-dimensional three-order dendritic structures. Previous studies show that split ring resonators (SRRs)
can be used to obtain magnetic resonance, thus sustaining surface waves behaving like surface plasmon polaritons (SPPs). In this paper, we obtain detailed results on surface plasmon polaritons of several different grating structures and theoretically prove that this kind of structures can sustain SPPs. Besides, since dendritic structures can be fabricated by double template-assisted electrochemical deposition, it is worth noting that fabrication of SPP-based materials might be much easier.     

金属-介质光栅结构表面等离子体耦合效率的模拟研究

表面等离子体可以将光子局域在金属表面附近, 并形成很强的近场能量密度, 可以大大提高金属表面附近分子的发光效率和光电转换吸收材料的利用率, 从而提高发光器件和光电转换器件的效率. 本文研究了在一维周期性金属-介质混合结构的光栅中表面等离子体激元的耦合条件, 给出了耦合效率随着结构和填充因子的变化, 并证明了在光栅的填充因子较高以至光栅的金属间隔较小时, 光子耦合成为表面等离子体的效率较高, 可以达到94%以上. 关键词： 表面等离子体激元 填充因子 光栅 吸收光谱