基于金属狭缝结构的表面等离激元全光调控

表面等离激元是束缚在金属-介质交界面上的一种电磁波模式,可突破衍射极限,被认为是下一代集成光子回路最有希望的信息载体。就几种表面等离激元金属狭缝结构的原理和应用做了简单概述。利用法布里-珀罗谐振腔、法诺共振、多模干涉等光学效应,这些金属狭缝结构可对表面等离激元的传输行为进行有效地调控。在理论和实验上,利用金属狭缝结构实现了亚波长表面等离激元单向激发器、亚微米宽带单向激发器、亚微米分束器、超紧凑纳米聚焦器件和亚微米全光开关等纳米光子器件。这些纳米光子器件在纳米集成光学中具有重要应用。     

All-optical Control of surface plasmon polaritons based on metal slit structures

表面等离激元是束缚在金属—介质交界面上的一种电磁波模式,可突破衍射极限,被认为是下一代集成光子回路最有希望的信息载体。基于我们的研究工作,就几种表面等离激元金属狭缝结构的原理和应用做了简单概述。利用法布里-波罗谐振腔、法诺共振、多模干涉等光学效应,这些金属狭缝结构可对表面等离激元的传输行为进行有效地调控。在理论上和实验上,利用金属狭缝结构实现了亚波长表面等离激元单向激发器、亚微米宽带单向激发器、亚微米分束器、超紧凑纳米聚焦器件和亚微米全光开关等纳米光子器件。这些纳米光子器件在纳米集成光学中具有重要应用。     

领结状金纳米二聚体耦合共振特性研究

利用有限元法对领结状金纳米二聚体结构的表面等离激元共振特性进行了探究,研究发现在几何形状保持不变的条件下,二聚体共振波长位移与粒子间距呈e的负指数变化,并且指数衰减系数与粒子大小无关。进一步分析了纳米结构附近电场分布,发现共振条件下单体结构的x轴和y轴电场分布都遵守e的负指数衰减规律,且场强与入射电磁波的偏振方向有关；而受二聚体间表面等离激元耦合因素的影响,二聚体之间的距离对场强的衰减速率有着巨大的影响。最后,对二聚体共振吸收强度进行了研究,发现吸收强度与二聚体距离之间的关系仍为e的负指数函数规律。本研究结果对微距传感、粒子捕获等具有重要的指导意义。     

Ag纳米粒子点阵的表面等离激元共振特性调控

通过纳米粒子束流气相沉积方法在衬底表面沉积稠密银纳米粒子点阵。通过对纳米粒子覆盖率的精细控制与纳米粒子点阵消光谱的实时监测,实现了其表面等离激元共振峰频率的系统调控。随着Ag纳米粒子密度的增加,点阵的表面等离激元共振波长发生红移,可逐步由小于400nm增大到570nm以上。研究发现,表面等离激元共振波长的变化与随纳米粒子沉积量增加而增加的紧密相邻的纳米粒子对的百分数相关。     

双缺口纳米环/纳米环腔中法诺共振效应的研究北大核心

应用时域有限差分法计算了由双缺口纳米环/纳米环腔构成的金纳米环复合体结构的消光光谱及其近场增强和电荷分布。计算结果表明,金纳米环复合体结构的光谱中出现了双重的法诺共振效应,通过改变外环缺口大小、外环的弧长以及内环大小,可以对复合体结构中法诺共振的调制深度和光谱位置进行大范围调谐。这些结果可指导金纳米环复合体结构用于纳米光子器件的设计,以满足其在表面增强喇曼散射和生物传感等方面的应用。     

表面等离激元波导-腔结构中的Fano共振

正表面等离激元Fano共振是由金属纳米结构中窄带的暗态和宽带的明态相互耦合产生的,由于它具有陡的非对称响应谱和场增强效应,因此在纳米光子器件中具有重要应用,如调制器、光开关、传感器等。利用有限元和散射矩阵理论相结合的方法研究了表面等离激元波导-腔结构中Fano共振的物理机制,包括耦合谐振腔效应、多模共振耦合效应等、基于上述表面等离激元波导-腔结构中的Fano共振,实现了分柬、光开关、传感器等纳米光子器件、由于表面等离激元波导具有亚波长束缚并在芯片上易于集成,这些基于表面等离激元波导-腔结构的纳米光子器件在高度集成光子回路中具有重要应用前景、     

等离激元纳米孔用于单分子光学检测的研究进展

等离激元纳米孔将等离激元天线与固体纳米孔结合,可限制待测物路径,并将入射光能聚集至路径中产生热点,从而增强场与待测物质的相互作用,在纳米尺度范围内实现高灵敏度检测,近年来已被广泛应用于单分子检测研究。本文概述了几种典型等离激元纳米孔结构及其场增强效果;分析讨论了4种目前常用的基于等离激元纳米孔的高灵敏度检测技术及其特点,包括荧光检测、表面拉曼增强光谱、表面等离激元共振位移传感以及光电结合方法;综述了等离激元纳米孔在脱氧核糖核酸（DNA）、蛋白质、肽等单分子光学检测方面的应用进展及典型成果;讨论和展望了等离激元纳米孔的未来研究趋势以及面临的机遇和挑战。     

基于石墨烯/光子晶体混合结构的石墨烯表面等离激元波导

由于石墨烯的无带隙线性能级结构,使得石墨烯等离激元具有能量局域强,响应频段宽,传播距离长,并可由偏置电压动态调控等优良特性。文章设计石墨烯与光子晶体的混合结构,利用光子晶体的能带结构和线缺陷的特点,形成了石墨烯表面等离激元波导,通过改变石墨烯的费米能级,实现了石墨烯表面等离激元波导频率的调控。     

表面等离子体受激辐射放大领结型纳米天线的SERS单分子探测(英文)

基于表面等离激子受激辐射放大原理,提出了一种应用于表面增强拉曼散射(SERS)单分子探测的领结型纳米天线结构。采用有限元方法(FEM)研究其局域表面等离子体共振(LSPR)和SERS特性。结果表明,该领结型纳米天线的局域表面等离子体共振强度和局域电场强度得到明显的增强,其散射截面为非表面等离激子受激辐射放大领结型纳米天线的1.1×104倍,局域电场强度为1×102倍。同时,该领结型纳米天线的表面增强拉曼散射增强因子最大达到1016,足以进行精确的单分子探测;整个纳米天线表面的增强因子也可达到1012,足以应用于单个生物分子的探测。     

HgCdTe反型层电子子能带物理

<正> 本文在4.2K下测定了p-HgCdTe MIS结构样品的量子电容谱,表面磁阻振荡,表面回旋共振以及表面电子自旋共振,确定了HgCdTe反型层电子子能带结构,包括能级位置、费米能级、有效质量、反型层耗尽层厚度等,并推导了由于自旋轨道相互作用而引起的电致自旋分裂子能带的色散关系和朗道能级扇形图,还研究了朗道能级以及自旋能级间的光跃迁问题。     

Double Fano resonances in disk-nonconcentric ring plasmonic nanostructures

The plasmonic properties of gold nanostructures composed of a disk outside a nonconcentric ring are numerically studied by the finite difference time domain(FDTD) method. Simulated results show that two Fano resonances are formed as a result of the coupling of the octupolar and quadrupolar modes of the ring with the dipolar mode of the disk. The reduction in structural symmetry causes a red shift of the Fano resonances and distinct changes in spectral lineshape by offsetting the center of the in...     

High-Q and Tailorable Fano Resonances in a One-Dimensional Metal-Optical Tamm State Structure: From a Narrowband Perfect Absorber to a Narrowband Perfect Reflector

Fano resonances giving rise to a rich variety of asymmetric spectral shapes have been investigated in optical nanostructures with multidimensional configurations. However, 1D nanostructure realizing Fano resonances with well-controlled spectral shapes are yet to be demonstrated. Here, the authors present both numerically and experimentally a 1D nanostructure exhibiting rich Fano resonances induced by interference between a lossy background (continuum) provided by a metal thin film and a discrete optical Tamm state (OTS). A drastic change in the Fano line shape occurs from a narrowband perfect absorber into a narrowband perfect reflector by controlling the metal thin film. Independent from the metal-related Fano profile, the OTS component determines the resonance frequency and guarantees a sharp resonance (with quality factors over 1000) on the flat mirror background. Taking advantage of its high-Q property, the structure can be developed into a dispersion device with subnanometer spectral resolution, which even enables a direct imaging of spectral information of molecular fingerprint. The authors believe that this work not only demonstrates a planar nanostructure with versatile Fano resonances for various applications but also provides physical insights into how a metal thin film can induce and significantly affect the Fano resonances in 1D optical resonators.     

石墨烯光栅太赫兹透射特性的研究

建立了石墨烯光栅模型,基于快速收敛傅里叶模型方法计算了太赫兹频段的石墨烯光栅透射率,讨论了费米能级、光栅周期、光栅占空比和弛豫时间对透射率的影响。研究结果表明,在正入射条件下,透射率随频率的增大先减小后增加,且费米能级、占空比和弛豫时间越高,透射率的最小值越小。在入射光频率为2 THz的条件下,透射率随入射角的增大先增加后减小,且透射率在入射角约为60° 时取得最大值。以上研究为石墨烯光栅的理论研究及其实际应用提供了有力指导。     

Resonance tunneling and nonlinear current in heterobarriers with complex law of carrier dispersion

New effects in resonance electron tunneling in a GaAs/Al_xGa_1?xAs/GaAs single-barrier heterostructure are analyzed with applied electric bias taken into account. Γ-X mixing of electron states at the interfaces is responsible for the Fano resonance in the barrier transmission coefficient. Trajectories of the Fano resonances and their interplay with the Breit-Wigner resonances in an electric field are studied. The current-voltage characteristic of the heterobarrier is calculated. A knowledge of the differential conductance makes it possible to obtain the Fano resonance profile and determine its parameters.     

基于硅基微环谐振器的Fano共振线型产生和调谐研究进展

Fano共振的线型具有明显不对称特征,在光学通信、调制和传感等领域中极具应用潜力。首先对微环谐振器的各种线型进行了介绍,强调了Fano共振线型的独特优势,其次依据结构分类梳理了国内外基于硅基微环谐振器产生Fano共振的研究现状,然后介绍了基于热光效应的Fano共振调谐的研究进展,最后展望了硅基微环谐振器的Fano共振的发展及应用。     

Independently tunable Fano resoances based on E-shaped cavity and its high performance sensing application

A novel nanostructure based on a simple metal-dielectric-metal (MDM) bus waveguide with sliver baffle as well as an E-shaped cavity is proposed to generate double Fano resonances arising from interference between broad continuous state and narrow discrete state. The commercial software COMSOL based on finite element methods is used to explore the Fano resonances properties and the senor properties of the system. According to the simulation results, it is demonstrated that E-shaped cavity can generate two discrete states, and the continuous sate is constructed by loading sliver baffle in bus waveguide. Moreover, it can be found that the Fano peak wavelengths and profiles can easily be tuned via structural parameters. Interestingly, the independent control of the left Fano resonance (LFR) can be accomplished by changing horizontal cavity length of E-shaped cavity. Meanwhile, our proposed nanostructure has a higher sensitivity of 1 440 nm/RIU as well as a higher figure of merit (FOM) value approximately 5 244. In conclusion, the proposed independently tunable Fano nanostructure may have a great promising in the fields of nanosensors, filters and other optical devices.     

Modulation of Fano resonances by an external magnetic field in semiconductor quantum wells

We have studied the dimensionality dependence of the behavior of Fano resonances in the photoluminescence excitation spectra of GaAs---Al_xGa_1−xAs heterostructures in a magnetic field applied in the Faraday configuration. A striking difference is observed between quasi-two and quasi-three-dimensional systems: while the Fano profiles evolve into Lorentzian lineshapes in two-dimensional systems, Fano resonances emerge from the continuum in three-dimensional-systems with increasing magnetic field.     

交叉蝴蝶结纳米结构的Fano共振效应用于表面增强相干反斯托克斯拉曼散射的理论研究

Fano共振效应拥有独特的局域场增强效果,在表面增强相干反斯托克斯拉曼散射中,不同波长局域场增强空间位置相同的结构结合Fano共振效应,可以实现混合频率共振模式,使得表面增强相干反斯托克斯拉曼散射总的增强因子得到大幅度提高。采用FDTD软件系统研究了对称的交叉蝴蝶结Au纳米结构的Fano共振效应,该效应使得交叉蝴蝶结结构中心位置附近的电场强度得到大幅度的增强,把该结构应用到表面增强相干反斯托克斯拉曼散射中,可以使表面增强相干反斯托克斯拉曼散射信号的增强因子高达1013,达到单分子检测的水平。     

氧化锌电子结构的压力效应的理论研究

基于平面波函数密度泛函理论研究了不同压力条件下纤锌矿结构氧化锌的晶格结构和电子结构。计算结果表明,氧化锌的晶格参数和Zn—O键长随外压力的增加先增大后逐渐减小,晶胞纵横轴长之比增大,晶格对称性保持不变;带隙类型均为直接带隙,其宽度随外压力增加先降低后逐渐增大,零压力下其存在着0.908eV的直接带隙,在最大压力100GPa下其带隙达0.993eV;费米能级附近的状态密度随压力增加有增大的趋势,电子局域化趋势明显。分析结果表明,随着外压力的增加,氧化锌费米能级下方附近的载流子有效质量先增大后减小;导带的载流子有效质量均较小。外界加力还改变了氧化锌体系的电子分布情况。