Coupling interaction between a single emitter and the propagating surface plasmon polaritons in a graphene microribbon waveguide

The coupling interaction between an individual optical emitter and the propagating surface plasmon polaritons in a graphene microribbon （GMR） waveguide is investigated by numerical calculations, where the emitter is situated above the GMR or in the same plane of the GMR, The results reveal a multimode coupling mechanism for the strong interaction between the emitter and the propagating plasmonic waves in graphene. When the emitter is situated in the same plane of the GMR, the decay rate from the emitter to the surface plasmon polaritons increases more than 10 times compared with that in the case with the emitter above the GMR.     

Tunable hybrid surface waves supported by a graphene layer

We study electromagnetic waves localized near the surface of a semi-infinite dielectric medium covered by a graphene layer in the presence of a strong external magnetic field. We demonstrate that a novel type of hybrid TE-TM polarized surface plasmons can propagate along the graphene layer. We analyze the effect of the Hall conductivity on the polarization properties of these hybrid surface waves and suggest a possibility to tune the graphene plasmons by the external magnetic field.     

Nano-infrared imaging of localized plasmons in graphene nano-resonators

We conduct in-situ near-field imaging of propagating and localized plasmons(cavity and dipole modes) in graphene nano-resonator. Compared with propagating graphene plasmons, the localized modes show twofold near-field amplitude and high volume confining ability(~ 10~6). The cavity resonance and dipole mode of graphene plasmons can be effectively controlled through optical method. Furthermore, our numerical simulation shows quantitative agreement with experimental measurements. The results provide insights into the nature of localized graphene plasmons and demonstrate a new way to study the localization of polaritons in Van der Waals materials.     

石墨烯等离激元的光学性质及其应用前景

石墨烯等离激元由于其独特的电学可调性、本征低衰减以及局域光场高度增强等特性, 引起了广泛的关注并迅速成长为一门新的学科分支--石墨烯表面等离激元光子学. 本文介绍了石墨烯等离激元的一些基本性质, 包括色散关系、局域的等离激元和传导的等离激元以及石墨烯等离激元对其周边介电环境的敏感性等. 在此基础上, 进一步介绍了石墨烯等离激元在太赫兹到中红外频段的应用, 比如有源光调制器的一些功能器件和增强的红外光谱探测等.     

Resonant surface plasmons of a metal nanosphere treated as propagating surface plasmons

On the assumption that the resonant surface plasmons on a spherical nanoparticle are formed by standing waves of two counter-propagating surface plasmon waves along the surface, by using Mie theory simulation, we find that the dispersions of surface plasmon resonant modes supported by silver nanospheres match with those of the surface plasmons on a semiinfinite medium-silver interface very well. This suggests that the resonant surface plasmons of a metal nanosphere can be treated as a propagating surface plasmon wave.     

Elastic surface waves guided by the edge of a slit

Surface waves propagating along the free surface of a homogeneous, isotropic, linearly elastic half-space, are shown to have the property that the normal displacement component at the free surface is governed by a reduced wave equation. This suggests a “membrane analogy”, and a corresponding family of surface waves. Of particular interest is a three-dimensional surface wave, whose displacement components in the sagittal plane vary linearly with the co-ordinate normal to that plane, while the displacement component in the direction normal to the sagittal plane is uniform in that direction. This new wave arises when surface waves propagate along the free surfaces of a semi-infinite slit, parallel to the edge of the slit, with the classical Rayleigh wave velocity. It is also shown that a semi-infinite slit cannot support surface waves which decay with the distance from the edge of the slit.     

Generation and near-field imaging of Airy surface plasmons

We demonstrate experimentally the generation and near-field imaging of nondiffracting surface waves, plasmonic Airy beams, propagating on the surface of a gold metal film. The Airy plasmons are excited by an engineered nanoscale phase grating, and demonstrate significant beam bending over their propagation. We show that the observed Airy plasmons exhibit self-healing properties, suggesting novel applications in plasmonic circuitry and surface optical manipulation.     

Airy plasmons: non‐diffracting optical surface waves

Airy beams represent an important class of non‐diffracting waves which can be realized on a flat surface. Being generated in the form of surface‐plasmon polaritons, such Airy plasmons demonstrate many remarkable properties: they do not diffract while propagating along parabolic trajectories, and they recover their shape after passing through obstacles. This paper reviews the basic physics of Airy plasmons in both paraxial and non‐paraxial cases, and describes the experimental methods for generation of Airy surface waves on metal surfaces, including a control of their trajectories, as well as the interference of Airy plasmons and hot‐spot generation. Many unusual properties of Airy plasmons can be utilized for useful applications, including plasmonic circuitry and surface tweezers. Picture: Observation of two colliding Airy plasmons.     

Effect of longitudinal excitations on surface plasmons

The influence of a longitudinal component in surface plasma waves propagating along the boundary between a plasma and vacuum has been investigated theoretically. It is found that the inclusion of the longitudinal component significantly modifies the dispersion relation for surface plasmons. In particular, it is shown that a surface plasmon can have any frequency in the interval from zero to the bulk plasma frequency.     

金属衬底上石墨烯的红外近场光学

对石墨烯/铜体系开展了系统性的近场光学实验研究,成功观测到了区别于铜衬底的、来自石墨烯的近场光学响应信号,发现在表面台阶几何参数相同的铜衬底上的不同石墨烯样品表现出了截然不同的近场光学响应.     

Surface plasmons at the interface between graphene and Kerr-type nonlinear media

The properties of surface plasmons localized at the interface between graphene and Kerr-type nonlinear substrates are investigated analytically. Although the relative propagation distance remains the same, the dispersion of graphene plasmons may be affected much by the inevitable nonlinear effect of substrates. Specifically, the wavelength of graphene plasmons can be tuned by adjusting the nonlinear permittivity of substrates.     

Selective excitation of multipolar surface plasmon in a graphene-coated dielectric particle by Laguerre Gaussian beam

Localized surface plasmonic resonance has attracted extensive attention since it allows for great enhancement of local field intensity on the nanoparticle surface. In this paper, we make a systematic study on the excitation of localized surface plasmons of a graphene coated dielectric particle. Theoretical results show that both the intensity and frequency of the plasmonic resonant peak can be tuned effectively through modifying the graphene layer. Furthermore, high order localized surface plasmons could be excited and tuned selectively by the Laguerre Gaussian beam, which is induced by the optical angular orbital momentum transfer through the mutual interaction between the particle and the helical wavefront.Moreover, the profiles of the multipolar localized surface plasmons are illustrated in detail. The study provides rich potential applications in the plasmonic devices and the wavefront engineering nano-optics.     

Plasmon mechanism of light transmission through a metal film or a plasma layer

It is shown that a smooth metal film (or a plasma layer) can be made transparent for an electromagnetic wave when two identical subwavelength diffraction gratings are placed on both sides of the film. The electromagnetic wave transmission through the metal film is caused by excitation of evanescent surface waves (plasmons) and their transformation into propagating waves at the gratings. A model which is developed analytically shows that the problem of the wave transmission is physically equivalent to the problem of excitation of two coupled resonators of evanescent waves which are formed at the two film surfaces.     

等离激元增强的石墨烯光吸收

石墨烯中等离激元具有特殊的光电性质,其和入射光的强烈耦合可以引起光吸收的增强.本文基于时域有限差分法和多体自洽场理论研究了等离激元对处于光学谐振腔中的石墨烯光吸收的影响.由于石墨烯中等离激元与入射光动量和能量不匹配而不能直接相互作用,因此石墨烯上施加了金属光栅结构.研究发现光栅结构能够对入射光进行动量补偿并且能够引起其下石墨烯中的电场强度产生很大程度增强,从而导致在该石墨烯结构中太赫兹等离激元和入射光发生强烈耦合而产生太赫兹等离极化激元,同时引起石墨烯光吸收的增强.希望本文能够加深对石墨烯光电特性的理解以及可以为基于石墨烯的太赫兹光电装置提供一定的理论依据.     

基于导模共振效应提高石墨烯表面等离子体的局域特性

本文构建了一种包含石墨烯和亚波长光栅的复合结构, 借助衍射光栅的导模共振效应, 在石墨烯表面激发高局域性表面等离子体激元, 研究了石墨烯与光栅结构对表面等离子体激元局域特性的影响规律, 并借助基于有限元法的COMSOL软件, 分析了缓冲层厚度、光栅周期、载流子迁移率和费米能级对石墨烯的表面电场、品质因子Q和有效模式面积S_eff的影响. 结果表明, 石墨烯表面等离子体激元的局域性在特定的参数点获得显著提高: 当μ = 0.7 m²/(V·s)时, 品质因子达到最大值Q_max = 1793; 当p = 235 nm或E_F = 0.72 eV时, 表面电场达到了入射光的3000倍以上. 强烈的局域性导致强烈 的光-物质相互作用, 因而本文提出的复合结构可实现高灵敏度传感器和高效率的非线性光学设备, 极大地扩展了石墨烯在纳米光学领域中的应用.     

Surface acoustic waves in an elastic wedge media

We consider surface acoustic waves in an elastic wedge media. It is established that the investigated waves substantially differ from known ones. For example, the movement of surface Rayleigh wave in the direction to the edge leads to a change of its structure, accompanied by the splitting of the initial wave to two separate modes and radiation of shift and longitudinal waves. Along the edge of the wedge the surface wave is strongly localized in the transverse direction. Are discussed the properties of the wedge antisymmetric normal waves, propagating parallel to the edge of the wedge.     

Acoustic analogue of graphene: observation of Dirac cones in acoustic surface waves

We demonstrate the presence of Dirac cones in the dispersion relation of acoustic waves propagating on the surface of a plate of methyl methacrylate containing a honeycomb lattice of cylindrical boreholes. This structure represents the acoustic analogue of graphene, the cylindrical cavities playing the role of carbon atoms while acoustic surface waves are the equivalent of electronic waves in graphene. Analytical expressions for the Dirac frequency and Dirac velocity in acoustics are given as a function of the radius and depth of boreholes. These parameters have been experimentally determined for a constructed structure and the data are in fairly good agreement with the predicted values.     

Coupling plasmons and dyakonons

We study the coupling of plasmons and Dyakonov surface waves propagating at the interfaces between isotropic-birefringent-metal layered structures. Efficient coupling is shown to occur with a proper choice of the crystal birefringence, the refractive index of the isotropic medium, and the light propagation direction relative to the crystal optical axis. In the case of low-loss metals, coupling efficiencies as high as 90% are predicted to be possible.     

Surface plasmon modes and the Casimir energy

We show the influence of surface plasmons on the Casimir effect between two plane parallel metallic mirrors at arbitrary distances. Using the plasma model to describe the optical response of the metal, we express the Casimir energy as a sum of contributions associated with evanescent surface plasmon modes and propagative cavity modes. In contrast to naive expectations, the plasmonic mode contribution is essential at all distances in order to ensure the correct result for the Casimir energy. One of the two plasmonic modes gives rise to a repulsive contribution, balancing out the attractive contributions from propagating cavity modes, while both contributions taken separately are much larger than the actual value of the Casimir energy. This also suggests possibilities to tailor the sign of the Casimir force via surface plasmons.