基于表面等离子体的非线性二次谐波增强效应

本文研究一种利用金属光栅结构激发表面等离子体,实现增强非线性二次谐波激发效率的方法.通过设计金属光栅周期、沟槽深度等结构参数,使其满足推导出的准相位匹配条件,实现泵浦光与倍频光的表面等离子体模式同时共振激发,得到高效输出的倍频光.文中利用时域有限差分方法对该方法进行了模拟仿真,验证了准相位匹配条件和共振激发表面等离子体模式对提高二次谐波输出的关键性作用,同时分析了光栅结构参数变化对二次谐波激发效率的影响规律.     

光波导显微技术测量微小厚度变化

在表面等离子波显微技术(SPM)的基础上,提出了一种新的反射型波导显微理论,并且进行了实验研究.这种显微技术采用棱镜波导耦合结构,在棱镜下底面依次镀有金属膜-波导层-样品层.利用导模共振吸收峰对样品层厚度敏感的特性,通过反射光强的测量来确定样品层厚度的变化值.和表面等离子波显微技术相比,光波导显微技术所采用的波导结构能够有效地削弱金属的吸收特性造成的影响,减小衰减全反射曲线的半峰全宽,进而提高波导显微对厚度变化的灵敏度.实验表明,光波导显微技术对厚度变化有很高的灵敏度.     

双侧波导同轴线耦合式线形微波等离子体源的研究

本文介绍了一种具有双侧波导同轴线耦合结构的新型微波等离子体源。通过电磁场模拟计算和等离子体发射光谱测量对同轴线耦合反应腔内部结构进行了优化,研究了线形等离子体源腔体结构对等离子体均匀性和长度的影响,并且在杆状样品表面进行了金刚石薄膜的沉积实验。实验结果表明:双侧波导同轴线耦合式新型线形等离子体源可以在引导天线表面产生圆柱状的线形等离子体,其等离子体的均匀性和长度受腔体内部结构的影响,在引导天线外径为4 mm,单侧模式匹配棒伸入量为10 mm的腔体结构下,等离子体的均匀性大于90%。通过对杆状样品表面不同位置处金刚石膜质量和等离子体沉积环境的测量,进一步验证了等离子体的均匀性。此外,线形等离子体的长度受引导天线长度和工作气压影响,这主要与反应腔内电磁场分布以及微波传输衰减有关。     

金纳米锥阵列与金薄膜耦合结构表面等离子体折射率传感研究

设计了基于SiO₂薄膜间隔的金纳米锥与金薄膜耦合结构表面等离子体共振折射率传感器。使用时域有限差分法研究了复合结构中的表面等离子体共振模式,复合结构不仅能够激发局域表面等离子体共振,也可激发传播表面等离子体共振。入射电磁波的能量部分通过单个金纳米锥耦合到局域表面等离子体,部分通过金纳米锥阵列二维光栅耦合到传播表面等离子体。在待测物折射率1.30～1.40的范围内,对复合结构的反射光谱进行了模拟研究,发现共振波长与分析物折射率呈线性关系,且由于局域和传播表面等离子体的高效激发,反射光谱共振峰处的反射率几乎为零。此外,在最优的金纳米锥几何参数下,传播表面等离子体共振模式的半高全宽非常窄,灵敏度和品质因数分别达到770 nm/RIU和113 RIU^-1,具有良好的折射率传感性能。所设计的复合结构作为表面等离子体共振传感器有望广泛应用于生物检测领域。     

10英寸场助热电子发射显示屏的制作

讨论了金属-绝缘体-半导体-金属结构的场助热电子发射显示(FAHED)器件的制作原理,简述了Mo/Ta2O5/ZnS/Au结构的10英寸FAHED的制作.通过电子束蒸发具有低功函数的上电极材料,适当控制其厚度,并且控制半导体层合适的厚度和成膜条件可以提高器件的电子发射率至0.3%.     

在实验室波导中单个简正波的传输和声反向散射的测量

我们的目的是为了在有限空间内进行“远场”声散射测量.我们使用了深度大约为35个声波长的厚波导并以第一号简正波激发它.该波导的顶部和底部为压力释放表面.为了仅用第一号简正波激发和接收,我们使用了垂直阵,该阵被振幅束控来同第一号简正波的本征函数相匹配.实验测量证实90%的能量是在第一号简正波内.用一对无方向性换能器作为探测发射器和接收器来校准散射测量系统.     

等离子体天线中波的色散关系的研究

本文研究了同轴对称表面波沿等离子体柱轴向传播的色散关系,由此得到的波矢说明了当频率小于等离子体频率时,电磁波沿等离子体柱的传播类似于电磁波沿金属介质交界面上的传播,传播速度接近于光速.因此可以使用等离子体代替金属用来构成最基本的天线振子.     

退火对高定向热解石墨的输运特性的影响

研究了退火对磁场诱导下高定向热解石墨(HOPG)输运特性的影响.结果表明,退火后HOPG的R-T曲线明显变得光滑,且退火后电阻率增大了近50%,相应温度下的磁电阻效应均减小约40%.分析认为,这是由于HOPG内部存在层错与所含杂质缺陷引起的.磁场下电阻率随温度的变化表明,外加磁场对低温下的金属导电行为存在抑制作用,随着外加磁场的增加,低温下的金属导电行为受到抑制,在H=5.57×104A/m时,低温下的绝缘体-金属转变(I-M)被完全抑制,呈半导体性质.随着磁场的继续增加,在磁场高于H=9.24×105A/m时再次出现绝缘体-金属转变,即再入型金属导电行为,且退火对这一转变过程没有影响,表明这种绝缘体-金属转变是由外加磁场诱导产生的.     

低温等离子体表面改性技术在金属生物材料中的应用进展

介绍了低温等离子体表面改性技术和金属生物材料的主要特性,概述了低温等离子体在金属生物材料表面改性中的应用进展,提出了等离子体改性中存在的主要问题,并对今后的研究和应用进行了展望.     

近红外强吸收金属纳米材料的制备和应用研究进展

近红外强吸收金属纳米材料由于在近红外区（750-1500nm）具有强烈的表面等离子体共振吸收，在众多领域具有极大的应用价值。将该类材料分为3种类型：各向异性金属纳米结构、金属复合纳米空心结构和非金属，金属复合纳米结构，分别介绍了它们的制备方法，并介绍了这类材料在生物医学领域的应用。     

Adiabatic description of superfocusing of femtosecond plasmon polaritons

A surface plasmon polariton is a collective oscillation of free electrons at a metal–dielectric interface. As wave phenomena, surface plasmon polaritons can be focused with the use of an appropriate excitation geometry of metal structures. In the adiabatic approximation, we demonstrate a possibility to control nanoscale short pulse superfocusing based on generation of a radially polarized surface plasmon polariton mode of a conical metal needle in view of wave reflection. The results of numerical simulations of femtosecond pulse propagation along a nanoneedle are discussed. The space–time evolution of a pulse for the near field strongly depends on a linear chirp of an initial laser pulse, which can partially compensate wave dispersion. The field distribution is calculated for different metals, chirp parameters, cone opening angles and propagation distances. The electric field near a sharp tip is described as a field of a fictitious time-dependent electric dipole located at the tip apex.     

Observation of Lateral Displacement of an Optical Beam Enhanced by Surface Plasmon Excitation

Abstract

The lateral shift of a light beam suffering total reflection can be enhanced by the excitation of a surface plasmon wave. A shift of ?19 μm was obtained in one total reflection at the surface plasmon resonance. A characteristic double-peak structure was observed in the reflected field as predicted by theory.     

Simulation of surface plasmon resonance of metallic nanoparticles by the boundary-element method

A set of new surface integral equations (Fredholm equations of the second kind) has been systematically derived from the Stratton-Chu formulation of Maxwell's equations for a two-dimensional TM mode to investigate the interactions of an incident electromagnetic wave with nanostructures, especially metals. With these equations, the surface components (the tangential magnetic field, the normal displacement, and the tangential electric field) on the boundary are solved simultaneously by the boundary-element method numerically. For nanometer-sized structures (e.g., dimension of 10 nm), our numerical results show that surface plasmon resonance causes a strong near-field enhancement of the electric field within a shallow region close to the interface of metal and dielectric. In addition, the corresponding pattern of the far-field scattering cross section is like a dipole. For the submicrometer-sized cases (dimension of several hundreds of nanometers), the numerical results indicate the existence of a standing wave on the backside surface of metals. This phenomenon could be caused by two surface plasmon waves that creep along the contour of metals clockwise and counterclockwise, respectively, and interfere with each other.     

Long-range surface plasmons on ultrathin membranes

A waveguide structure supporting long-range surface plasmon waves in any gaseous or liquid environment is described. The waveguide comprises a large area dielectric membrane of nanometric thickness upon which thin metal stripes and features are deposited. This structure allows the environment to surround the stripe thus ensuring that an essentially symmetric dielectric background is always present, as required to support the wave. The membrane perturbs the wave in a manner that significantly increases its surface sensitivity. The high surface sensitivity in concert with the ability to create long optical interaction length plasmonic structures leads to high sensitivity (bio)chemical sensors. Theoretical results describing the operation of the structure are given along with experimental results demonstrating the propagation of long-range surface plasmons in air and in liquid. The structure opens up a wealth of opportunities for research and application across many fields, including plasmonics, photonics, material science, surfaces, and solid-liquid interfaces.     

基于亚波长光学谐振腔的纳米聚焦器件

提出了一种基于亚波长金属光学谐振腔的纳米聚焦器件.通过利用亚波长金属结构激发表面等离子体波在谐振腔中发生干涉,形成驻波条纹,并被耦合进相邻的锥形微尖结构中,从而在锥形尖端进行聚焦,焦斑的尺寸达100nm.研究表明:通过改变亚波长光学谐振腔的长度,可以对聚焦能量进行连续调制.利用电磁仿真软件FDTD进行了针对性仿真,描绘出该器件的强度分布图,揭示出其内在工作机理,并总结出能量聚焦的规律.     

Filters based on spoof surface plasmon polaritons composed of planar Mach–Zehnder interferometer

Abstract

Filter characteristics of a planar Mach–Zehnder interferometer (MZI) structure composed of periodically thin corrugated metal films were studied here. From theoretical simulation, spoof surface plasmon polaritons can propagate along the periodically thin corrugated metal films in microwave frequency, which can be excited by a coplanar waveguide. When the two arms of the MZI have the same length with the angle between them being 60°, the MZI structure has a very wide bandwidth with 8.6 GHz. By changing the length of one of the interference arms, a novel low-pass filter based on the planar MZI structure with two notched frequencies was proposed. The proposed planar structure can find potential applications in developing surface wave devices in integrated microwave circuits and systems.     

Observation of Rabi splitting from surface plasmon coupled conduction state transitions in electrically excited InAs quantum dots

We demonstrate strong coupling between a surface plasmon and intersublevel transitions in self-assembled InAs quantum dots. The surface plasmon mode exists at the interface between the semiconductor emitter structure and a periodic array of holes perforating a metallic Pd/Ge/Au film that also serves as the top electrical contact for the emitters. Spectrally narrowed quantum-dot electroluminescence was observed for devices with varying subwavelength hole spacing. Devices designed for 9, 10, and 11 μm wavelength emission also exhibit a significant spectral splitting. The association of the splitting with quantum-dot Rabi oscillation is consistent with results from a calculation of spontaneous emission from an interacting plasmonic field and quantum-dot ensemble. The fact that this Rabi oscillation can be observed in an incoherently excited, highly inhomogeneously broadened system demonstrates the utility of intersublevel transitions in quantum dots for investigations of coherent transient and quantum coherence phenomena.     

Optimization of plasmon excitation at structured apertures

Surface plasmon excitation that is due to a single or a structured circular aperture in a flat metallic screen is investigated theoretically and numerically with a view to enhancing the electric field close to the metallic surface. A systematic study of the homogeneous solution of the electromagnetic scattering problem is made with cylindrical coordinates, expanding Maxwell equations on a Fourier-Bessel basis. A perturbation analysis devoted to simple physical analyses of different types of cylindrical nanostructure is developed for the optimization of plasmon excitation by a normally incident linearly polarized monochromatic plane wave. The conclusions drawn from this analysis agree well with the results of rigorous electromagnetic calculations obtained with the differential theory of diffraction in cylindrical coordinates.     

Multi-mode cylindrical surface wave excitation

In this paper, we study the solution of the 3-dimensional reduced wave equation above an infinite plane 2-dimensional surface wave supporting structure. The structure is simulated by a multiple impedance boundary condition that allows for the excitation of two different cylindrical surface wave modes. At first we investigate the problem of a simple source which is then generalized to multi-pole sources. For the cases considered, we are able to give an explicit solution that exhibits the character of the surface wave field. Furthermore, using a virtual structure notion, we are able to identify the power travelling within the impedance structure associated with a given external surface wave mode. Thus, a definition of the total surface wave power is applied in a manner that modal power flow separability is maintained. The far field pattern is observed to vanish in certain directions, in particular along the impedance plane. Furthermore, the far field power is calculated in terms of a non-elementary definite integral which is then estimated at high and low frequencies so that a partial verification of our calculations can be made by observing that power is conserved to these orders.     

Plasmon field enhancement in silver core-protruded silicon shell nanocylinder illuminated with light at 633 nm

We show, to the best of our knowledge, the first simulation result of the strong plasmonic field coupling and enhancement at the Ag/Si interface of a silver core/protruded silicon shell nanocylinder by using the finite-element method. The strong plasmon field, with a slow effective phase velocity accumulated at the Ag/Si interface, which results from the large effective index of the surface plasmon due to the nearly identical real parts with opposite signs of the permittivities of silver and silicon at 633 nm, is analyzed. When the silicon shell has shallow protrusions of proper periodicity to meet the phase matching condition between the incident light and the surface plasmon wave at the Ag/Si interface, a higher scattered electric field and a higher sensitivity to the refractive index change of the surrounding medium can be achieved. Furthermore, a feasible implementation of the core-shell nanocylinder design concept is studied and discussed.