金属纳米线阵列的光学非线性增强因子的分析和计算

以平行排列的无限长金属圆柱体为模型,基于金属颗粒与电磁场相互作用的平均场理论和非线性光学的基本理论,计算了局域场增强和表面等离子体共振引起金属纳米线阵列的光学非线性增强,通过理论计算得到了银纳米线阵列的局域场增强因子和有效三阶非线性极化率的增强因子,并分析了不同参量和非参量非线性光学效应总的场增强因子.     

金属等离子激元调控Fabry-Perot微腔谐振模式研究（英文）

目前,利用氧化锌(ZnO)微纳米线结构形成具有自然谐振腔的紫外激光器件引起国内外广泛关注。针对ZnO本征缺陷导致器件发光及稳定性不足等问题,开展金属局域等离子激元局域场发光增强方面的研究,对ZnO基紫外激光器件的应用具有十分重要的意义。本文通过理论仿真构建氧化锌微米线结构模型,对微腔光学损耗及Fabry-Perot(F-P)谐振腔模式演化进行了理论分析。得到ZnO微腔直径变化与F-P谐振模式演化、光学损耗和光强分布的关系。在此基础上通过金属Ag纳米颗粒对ZnO微米线6个表面进行修饰,发现金属局域表面等离子激元共振耦合效应对微腔周围的损耗光有明显的抑制作用,并且在金属与微腔的交叉区通过共振耦合效应实现局域场增强。模拟结果表明,在损耗较大的微腔表面修饰Ag纳米颗粒以后,光场限域能力提高6. 72%,而在金属颗粒之间沿X轴方向产生二次耦合现象,其电场强度更有2倍的增强效果。     

Ag-Al纳米球二聚体的光学性质研究

金属纳米材料因其表面等离子体共振特性而备受关注。异质结构的金属纳米材料的光学特性相比于同质结构因其材料的不同破坏了原有结构的对称性,对称性的破坏将引起光学性质的改变,相邻两个颗粒之间的相互作用会产生Fano共振。Fano共振是由异质纳米结构的表面等离子体共振耦合引起的,通过合理地调控表面等离子体共振的耦合,将进一步调控Fano共振的强度同时促使异质结构的电场增强特性和辐射特性得到进一步优化。受金银等贵金属的带间跃迁影响,金属铝纳米材料成为研究紫外-近紫外光区的表面等离子体共振研究最佳选择。采用有限时域差分方法研究了Ag-Al纳米球二聚体的光学特性。研究了Ag和Al纳米球组成的二聚体的吸收光谱与入射光偏振方向、纳米球半径、颗粒间距和介质折射率等几何结构及物理参数的关系,并深入讨论了二聚体的局域场分布规律;讨论了获取更高效的Fano共振光谱的方法。由于材料的对称性被破坏,异质二聚体的光学性质与同质二聚体明显不同,Ag-Al异质纳米球二聚体呈现出在紫外和可见光区的双Fano共振现象。Ag-Al二聚体表面等离子体互相耦合引起Fano共振从而导致表面等离子体的共振抑制和增强。研究结果对在紫外-可见光区的表面等离子体应用、纳米光学器件的设计与开发及基于表面等离子体共振的表面增强光谱、生物传感和检测研究等有一定参考价值。     

表面等离激元纳米聚焦研究进展

表面等离激元是束缚于金属纳米结构表面的电磁模式,具有突破光学衍射极限和局域场增强等特点.当表面等离激元沿一维锥形纳米结构表面传播时,由于纳米聚焦效应,使得等离激元能量汇聚于锥形结构的纳米尖端,从而在该位置产生巨大的局域场增强.这一现象为电磁场能量在纳米尺度的定向输送提供了十分有效的路径,在分子光谱增强及传感领域得到广泛的应用.本文对近年来表面等离激元纳米聚焦在纳米光子学领域的研究进展进行了综述,并展望了这一领域未来的发展方向.     

表面修饰基团对金纳米颗粒非线性光学效应的影响研究

采用两相法分别制备一级硫醇修饰和二级十六烷基三甲基溴化铵(CTAB) 修饰的金纳米颗粒,通过透射电子显微镜和紫外-可见吸收光谱表征了其结构和线性光学性质. 采用开孔Z扫描技术,研究表面修饰对金纳米颗粒在532 nm波长激光作用下的非线性光学效应及光限幅性能的影响行为.结果表明,二级CTAB的修饰增强了颗粒在激光照射下的局域场作用, 并提高了热电子对非线性光学效应的贡献程度,从而有效地提高了金纳米颗粒的光限幅性能.     

金属纳米颗粒等离激元共振增强非线性介质谐波的发展现状

随着纳米加工和制备技术的不断发展,金属纳米粒子的等离激元光学特性已得到了广泛的研究与应用。本文基于金属纳米颗粒等离激元共振特性,分析了金属纳米颗粒等离激元共振对介质谐波的增强机制,综述了该增强机制在近几年所取得的最新研究成果及其在生物成像领域的应用。金属纳米颗粒等离激元共振在增强介质非线性特性领域的发展趋势是从简单的金属纳米颗粒向复杂形状纳米颗粒和金属纳米颗粒组装体的发展,这些新型金属纳米颗粒在非线性光学、生物医学上的疾病诊断和治疗有良好的实际应用前景。     

金纳米双球系统的高灵敏光学传感与其消光系数及局域场增强之关联

系统地研究了最基本的单/双金纳米球系统的共振峰移动、局域场增强和消光谱等光学响应行为.发现在双金纳米球系统中,入射光除了能激发每个金纳米球的局域表面等离激元共振模式外,调整金纳米球间隙可使共振模式间产生强烈耦合,使系统局域场增强因子进一步提升,并增强光学传感能力和消光系数.有趣的是,受限于有限的局域场增强体积,具有高局域场增强因子的间隙为2 nm的双金纳米球系统的消光系数大幅降低,其消光系数和光学传感能力均低于5 nm间隙的系统.研究表明,双金纳米球系统的光学传感灵敏度不是由局域场增强幅度直接决定的,而与系统消光系数有相似的变化行为.这些结果可指导金纳米双颗粒和多颗粒系统的设计,为表面拉曼散射增强和光学传感等方面的应用提供创新性思路和方案.     

局域表面等离激元

局域表面等离激元使得贵金属纳米颗粒具有丰富的光学性质,其应用涵盖能源、生物医学、安全、信息、超材料等诸多领域。文章简要介绍局域表面等离激元的基本性质、贵金属纳米结构中的局域表面等离激元共振耦合以及具有局域表面等离激元特性的贵金属纳米结构的一些重要应用。     

表面增强光学力与光操纵研究进展

金属纳米结构在光激发下产生的表面等离激元,可导致亚波长光场局域、近场增强等效应,在表面增强光谱、超灵敏传感、微流控芯片、光学力等方面有重要的应用.对于光学力而言,首先,由于表面等离激元共振及其导致的电场增强对于入射波长、几何结构等具有较强的依赖性,而光学力又与电场分布密切相关,所以可利用光镊(会聚光束)来操纵或筛选金属纳米颗粒;其次,入射光激发金属纳米颗粒聚集体后,在间隙形成的较大的近场增强和梯度,也可看作一种"等离激元镊",用于操纵其他颗粒;最后,当入射光的偏振改变甚至为新型光束的情况下,光学操纵将具有更高的自由度.本文首先简要介绍了表面等离激元增强光学力的计算;之后围绕光镊作用于等离激元金属纳米颗粒,等离激元镊作用于其他颗粒,与偏振、新型光场或手性结构相关的等离激元光学力这三个方面,综述了近年来表面等离激元金属纳米颗粒光学力和光操纵的一些新进展;最后提出了表面增强光学力与光操纵的若干研究趋势.     

微纳光学结构与太赫兹辐射产生技术的研究进展

太赫兹(THz)技术在基础研究与产业应用中具有重要研究意义,但其广泛应用仍受限于高效、紧凑的THz源,特别是0.5～2.0 THz波段。目前,人们已经采用了多种技术产生THz辐射,基于光学的方法是其中最重要的手段。首先,针对THz脉冲波及连续波,基于光电导效应及非线性光学差频的THz辐射产生机理,总结了近年来微纳光学结构在提高泵浦光至THz转换效率上的应用。然后,分析了金属纳米光天线通过增强泵浦光局域电场提高THz辐射效率和将金属纳米光天线作为THz辐射源两种增强情况。最后,展望了其他类型的光学微纳结构,尤其是全介质光学天线支持的米氏谐振、无辐射模式以及连续域中束缚态等新颖物理现象在THz辐射产生中的增强作用。     

Recent Advances of Light Propagation in Surface Plasmon Enhanced Quantum Dot Devices

Surface plasmons are of particular interest recently as their performance is approaching the enhancement of light emission efficiencies, after synthesized close to the vicinity of solid state materials, i.e., semiconductor structure. As other scientific works have been proposed to improve the light-emitting efficiency, such as the use of resonant cavities, photon recycling, and thin-light emitting layers with periodic surface texturing, surface plasmon possesses a promising way to the light enhancement, due to the energy coupling effect between the emitted photons from the semiconductor and the metallic nanoparticles fabricated by nanotechnology. The usual pathway of plasmon enhanced light emitting devices is the use of Ag/Au nanoparticles coating the surface of semiconductor quantum dot (QD) or quantum well (QW) structures. However, apart from efforts to extract as much light as possible from single-driven surface plasmon-QD/QW, it is possible to enhance the light emission rate with double optical-excitations. This approach is based on the quantum interference between the external lasers and the localized quantum light, and promised to stimulate the development of plasmon-enhanced optical sensors. In this review, we describe the quantum properties of light propagation in hybrid nanoparticle and semiconductor materials, i.e., quantum dot or nanomechanical resonator coupled to Ag/Au nanoparticles, driven by two optical fields. Distinct with single excitation, plasmon-assisted complex driven by two optical fields, exhibit specific quantum interference characteristics that can be used as sensitive all-optical devices, such as the slow light switch, nonlinear optical Kerr modulator, and ultra-sensitive mass sensing. We summarize the recent advances of light propagation in surface plasmon-enhanced quantum dot devices, driven by two optical fields, which would stimulate the development of novel optical materials, deeper theoretical insights, innovative new devices, and plasmonic applications with potential for significant technological and societal impact.     

Nonlinear optical characteristics of CdS and ZnS nanoparticles implanted into zirconium oxide thin films

The nonlinear refractive indices γ and nonlinear absorption coefficients of ZrO₂ films doped with CdS or ZnS nanoparticles, as well as with various metals, are measured. The effects of semiconductor and metal nanoparticles and annealing on the nonlinear optical properties of films are studied. The structural parameters of films, determined by electron microscopy and x-ray dispersion spectroscopy, are compared to the optical and nonlinear optical characteristics of these media. The high magnitude of γ of the films ((3±0.6)×10^?11 cm² W^{? 1}) is attributed to the surface enhancement effect in semiconductor nanoparticles. On the basis of Z-scan data obtained at different intensities of radiation, it is shown that the variations in γ of the ZrO₂:CdS(Cr) and ZrO₂:ZnS(Mn) films are related to the generation of free carriers.     

多波长飞秒激光激发下GaAs纳米线SHG特性研究

本文基于有限元法研究了直立生长于GaAs衬底的GaAs纳米线的光场响应和光场增强性质. 实验使用多个波长的飞秒激光脉冲激发GaAs纳米线, 测得了较高效率的二次谐波信号, 并首次使用宽带超连续飞秒脉冲 (1000–1300 nm) 在纳米线上获取了宽带、无杂散荧光噪声的二次谐波信号. 这种高效的二次谐波产生过程主要归因于纳米结构引起的局域场增强效应. 本文阐明了GaAs纳米线的二次谐波倍频特性, 这些结果对于其在纳米光学中的光器件、 光集成等领域的进一步研究和实际应用具有很好的参考价值. 关键词： GaAs纳米线 二次谐波 飞秒激光     

Third-order nonlinear optical response in quantum dot–metal nanoparticle hybrid structures

Third-order nonlinear optical response of a semiconductor quantum dot, modulated by the metal nanoparticle (MNP), has been studied by using the effective mass and the rotating wave approximation. Considering multiple effects in the local and nonlocal optical response of the MNP, the dependence of the dispersion and the absorption on the size of the hybrid system are investigated in detail. By controlling the geometrical parameters of the hybrid structure and the direction of the electric field polarization, a significant enhancement of the nonlinear response is shown. The enhancement factor is nearly two orders of the magnitude, which is consistent with the experiment. Compared to the results obtained with the local effect, the center frequency shows blueshift obviously in the case of the nonlocal effect. In particular, the presence of the MNP leads to a strong absorption band appearance, which promises applications in the field of light transmission and the optical switching.     

An all optical frequency encoded demultiplexer with tri-state logic

Optics has already been established its significant application over electronics using the nonlinearity of optical medium. The use of semiconductor optical amplifier (SOA) as a nonlinear medium has remarkably extended in the field of optoelectronic technology due to his high switching speed and high extinction ratio. The SOA based devices are used in multifunctional way mainly in switching, multiplexing, de-multiplexing and wavelength conversion. Here in this paper the authors propose a new demultiplexer scheme with the broad area semiconductor optical amplifier (BSOA) using the frequency encoding techniques and tri state logic. Frequency encoding techniques and tri-state logic in optics are already been established as a potential mechanism.     

飞秒激光共振增强腔的理论与实验研究

飞秒激光共振增强腔在非线性光学、 精密光谱学等研究领域有重要应用, 尤其是近年来已成为产生高重频紫外光梳的强大工具. 采用循环稳定电场方法分析了飞秒激光脉冲在共振 增强腔中的增强和色散特性,给出了增强倍数与 精细度的关系及共振带宽与精细度和腔内色散量的关系. 实验上实现了175 MHz, 15 fs的宽谱飞秒激光脉冲的共振 增强,增强倍数约为10倍左右.     

How to measure chi(3) of a nanoparticle

Most of the known methods to measure the nonlinear optical properties of materials deal with the bulk properties, but there are many demanding applications that require those measurements to be done on a single particle or a single molecule. We report a novel application of nonlinear optics to measure the third-order nonlinear optical susceptibility of nanoparticles in solutions. By measuring the power of the third harmonic generated in a diluted solution of nanoparticles, both the size and chi(3) can be extracted from a simple set of measurements.     

Surface-enhanced raman scattering and nonlinear optics applied to electrochemistry

The most recently developed diagnostic technique in metal-electrolyte and metal-gas interfaces adapts spontaneous Raman scattering and nonlinear optical generation, techniques normally applied to bulk media, to surface science investigation. For certain metallic surfaces, an enormous increase exists in the Raman (as much as 10⁶ to 10⁸ times) and nonlinear optical signals resulting from submonolayer coverage of molecular adsorbates at the interface. Spontaneous Raman scattering and nonlinear optical scattering are well developed in both theory and practice for the analysis of molecular structure and concentration in bulk media. Instrumentation to generate and detect these inelastically scattered signals is readily available and is adequate for adaption to surface science. However, the mechanism (or mechanisms) giving rise to such a large enhancement at the interfaces is still being actively researched and remains controversial. Theoretical and experimental investigations related to the underlying physics of this enhancement and the application of such surface enhancement as a vibrational probe for adsorbates on the metal surface have been labeled “surface-enhanced Raman scattering” (SERS) and “surface-enhanced nonlinear optics”. Soon after the recognition that molecules adsorbed onto metal electrodes under certain conditions exhibit an anomalously large Raman scattering efficiency,^1–3 it became evident that such a phenomenon makes possible an in situ diagnostic probe for detailed and unique vibrational signatures of adsorbates in the ambient phase (electrolyte and atmospheric gas surroundings). Optical spectroscopy in the visible range has a much higher energy resolution (e.g., 0. I cm-I) than is presently available in electron energy loss spectroscopy (EELS), as well as the capability to measure much lower frequency modes (e.g., as low as 5 cm^?1) than is possible in infrared spectroscopy. Perhaps the most significant attribute of SERS and surface-enhanced nonlinear optical scattering is that the surrounding media in front of the interface (e.g., several meters of gas and several centimeters of liquid) do not introduce optical loss or overwhelmingly large signals. The recognition that SERS is capable of performing vibrational spectroscopy with this resolution, frequency range, and in such dense surroundings has therefore brought an explosion of activity to the field since 1977.