表面等离子体共振技术的一些新应用

介绍了表面等离子体共振技术在表面等离子体共振传感器、扫描近场光学显微技术、薄膜光学和膜厚测量、全息成像技术、Q开关、精密角度测量等领域的新应用.     

纳米尺度的光学成像与纳米光谱———近场光学与近场光学显微镜的进展

近场光学是指当光探测器及探测器－样品间距均小于辐射波长条件下的光学现象．利用近场光学扫描显微镜和近场光谱仪，不但能够以突破衍射极限的超高分辨率在纳米尺度实现光学成像，而且还可获得纳米微区的光谱信息．文章介绍近场光学的原理及其在凝聚态物理领域中的应用与进展，并给出了我们的初步结果     

双椭圆纳米金属棒构成的表面等离子体波导的传输特性分析

设计了一种双椭圆纳米金属棒表面等离子体波导,采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率和传播长度随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个椭圆金属棒所形成的中间区域,且越靠近金属棒的弧形边,沿纵向的能流越大.通过调节两个金属棒的中心距离以及它们的两个半轴的大小,可以调节模式的有效折射率和传播长度.在工作波长确定的条件下,相对于a=b的情形来说,在a<b时,场与金属表面接触的面积较大,场关键词：集成光学光波导表面等离子体波导     

纳变尺度的光学成像与纳米光谱：近场光学与近场光学显微镜的进展

近场光学是指当光探测器及探测器一样品间距均小于辐射波长条件下的光学现象，利用近场光学扫描显微镜和近场光谱仪，不但能够以突破衍射极限的超高分辨率在纳米尺度实现光学成像，而且还可获得纳米微区的光谱信息，文章介绍近场光学的原理及其在凝聚态物理领域中的应用与进展，并给出了我们的初步结果。     

扫描近场光学显微镜中两类光纤探针传输特性的研究

采用局域模式耦合理论，对扫描近场光学显微镜中的两类光纤探针－腐蚀锥和熔拉锥的传输特性进行了比较和分析。给出了光在探针锥中传输时耦合效率的分布情况，以及传输效率随锥长，针尖直径和光波长变化的特性。     

蝴蝶形中空表面等离子体波导的传输特性

本文设计了一种蝴蝶形中空表面等离子体波导,并对其传输特性进行了研究.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何参数和工作波长的变化关系进行了分析.结果表明:沿纵向的能流主要分布在由四个圆洞所构成的上下两个尖角之间的区域,且越接近尖角,沿纵向的能流越大.对中空圆洞的半径、上下两排圆洞圆心间横向距离和左右两列圆洞圆心间的纵向距离进行调节,模式的有效折射率、传播长度和模式面积也随之变化.在工作波长确定的条件下,相对于b=r/4的情况来说,当b=r/2时,上下两个尖角之间的距离较大,场与金属的相互作用较弱,有效折射率就较大,传播长度也较大.在几何参数确定的条件下,相对于λ=705.0 nm的情形来说,在λ较大时,场的分布范围较大,场与金属表面的接触面积较大,场与金属的相互作用较弱,有效折射率较小,传播距离较长.与由两个和三个空心圆柱构成芯区的表面等离子体波导相比较,蝴蝶形中空表面等离子体波导具有良好的传输特性.如果在波导结构中心填充增益介质,可以克服较大的传播损耗,因此这种蝴蝶形中空表面等离子体波导可以用于光子器件集成领域和传感器领域.     

领结形中空表面等离子体波导的传输特性

设计了一种领结形中空表面等离子体波导.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个上下突起所形成的中间区域.通过调整几何参数及工作波长,可以调节模式的有效折射率、传播长度和模式面积.在工作波长确定的条件下,有效折射率随突起半径的增大呈减小趋势,而传播长度和模式面积则随着突起半径的增大呈增大趋势,四个角上的圆弧半径对波导的传输特性有微调作用,左右扇形区域的半径对波导的传输特性有较明显关键词：集成光学光波导表面等离子体波导     

用扫描近场光学显微镜技术研究金膜表面等离体子共振

表面等离体子波(SPW)可与入射光横磁波极化能量耦合并被共振激发,这种现象被称为表面等离体子共振现象(SPR)。主要利用扫描近场光学显微镜(SNOM)技术和表面等离体子共振现象技术相结合,来研究金膜表面等离体子共振。设计并建立了结构独特的新型Kretschmann型表面等离体子共振现象耦合装置,同时又设计了具有厚度梯度的表面等离体子的制备方法。在此基础上,测量了改变入射角条件下的表面等离体子共振曲线,测得该装置的等离体子共振角灵敏度为1°。并且对金膜表面进行表面等离体子共振条件下的扫描近场光学显微成像。实验结果表明,在共振时金膜表面的扫描成像比不共振时清晰,而且增加了很多细节。应用表面等离体子共振现象技术将可以明显提高扫描近场光学显微镜的信噪比、分辨力等性能。     

扫描近场红外显微镜近场距离控制系统的改进

针尖 样品的距离控制系统是扫描近场红外显微镜的重要组成部分。切变力探测作为一种重要的近场距离控制手段而得到了广泛的应用。介绍了一种对切变力探测系统的改进方法 ,它可以有效地提高石英晶振音叉的品质因数 ,进而提高探测系统对切变力感应的灵敏度。给出了理论分析和实验验证结果     

硅基混合表面等离子体纳米光波导及集成器件

总结并展望了硅基混合表面等离子体纳米光波导及集成器件方面的理论和实验研究工作。首先介绍了几种硅基混合表面等离子体纳米光波导结构,其尺寸可小至100 nm以下,而传播长度达100μm量级;其次介绍了基于硅基混合表面等离子体纳米光波导的功分器、偏振分束器和谐振器等集成器件,其尺寸为亚微米量级;最后探讨了硅基混合表面等离子体纳米光波导与硅纳米线光波导的耦合及对其进行增益补偿。     

Near field optics and light confinement

By exploring the surface of an illuminated object at a very short distance by means of a subwavelength detector, it is possible to reconstruct images whose resolution is beyond the diffraction limit. This opportunity due to the properties of near fields can be explained in terms of non radiating field detection. Such a detection is the basis of near field microscopy. In this communication emphasis will be put on some fundamental aspects of the new concept of non radiative optics such as the relation between Rayleigh criterion and Heisenberg principle and the notion of light confinement. Some proposals of non radiative transfers will be evoked.     

Microdisk resonator filters made of dielectric-loaded plasmonic waveguides

Microdisk resonator filters, an alternative to microring resonator filters, are studied by means of vectorial three dimensional finite element method simulations. Their performance characteristics are highlighted for different microdisk radii, and compared with those of the respective, footprint-wise, microring filters. We show that microdisk filters are advantageous, as the resonator involved exhibits smaller radiation losses. Extinction ratios as high as 30 dB are possible by properly tuning the gap separating the waveguide from the microdisk in each case. Transmission dips due to higher-radial-order modes that drastically change the transmission picture appear only for very large microdisk radii.     

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.     

Resonantly enhanced transmission of light through subwavelength apertures with dielectric filling

Using both analytical and numerical methods to study transmission of light through dielectric-filled subwavelength apertures in a real metal, we have found that a propagating mode can in principle exist inside a waveguide of arbitrary small size if a particular relationship between the dielectric constants of the cladding and filling materials at the incident frequency is satisfied. Practical transmission through a subwavelength aperture of finite depth can be enhanced when the depth is such that Fabry-Pérot-like resonances are excited. For 810 nm light incident on a silicon-filled 50-nm-diameter aperture in a 200-nm-thick gold film, we found that a normalized near-field intensity ratio of 1.6 at the exit can be achieved. This resonantly enhanced transmission phenomenon may be advantageously applicable to near-field scanning optical microscopy and single-molecule spectroscopy.     

Dual mode near-field scanning optical microscopy for near-field imaging of surface plasmon polariton

In this paper, we theoretically and experimentally demonstrate that metal coated apertured probes are efficient near-field probes on surfaces with high reflectivity for the scattering as well as for the collection mode near-field scanning optical microscopy (NSOM). We show that a blunt apertured metal coated tip is very effective in suppressing image dipoles which affect strongly the signals scattered from frequently used sharp metal tips or gold nanoparticle attached probes. By using a simultaneous collection and scattering mode (dual mode) NSOM we measure the near-field images of surface plasmon polariton (SPP) launched from a slit. The collection mode measures propagating SPP along lateral distance in a long scan range with high signal-to-noise ratio, and the scattering mode measures the polarization resolved near-field of SPP. Comparisons of the measured data obtained in the dual mode enable to easily characterize SPP and to separate the measured near-field into the propagating SPP and the directly transmitted light.     

Surface plasmon-assisted optical switching/bistability at telecommunication wavelengths in nonlinear dielectric gratings

In this paper, we numerically investigate nonlinear optical responses in dielectric gratings coated by flat metallic surface, where the structural parameters are chosen for wavelengths of operation at the telecom regime. The presented designs show the output light reflection with respect to the incident intensity of increasing, decreasing, and non-monotonic belt-shape functions. Nonlinear optical responses including switching and bistability appeared in the telecom region owing to assistance of surface plasmon resonance excited at the metal/dielectric interface, which enhances the diffraction efficiency and induces the momentum matching for the leaky modes of the dielectric grating. This results in electric intensity-effective refractive index dependence enhancement in the Kerr nonlinear media. Our design and investigation of the linear and nonlinear optical responses will provide a general guideline for a hybrid metallic-dielectric structure-based optical switching/bistability device design.     

Surface plasmon resonance based fiber optic sensor utilizing indium oxide

A highly sensitive surface plasmon resonance (SPR) based fiber optic sensor with indium oxide (In₂O₃) layer coated on the core of the optical fiber is presented and theoretically analyzed. The sensitivity of the SPR based fiber optic sensor has been evaluated numerically. It is shown that the proposed SPR based fiber optic sensor with In₂O₃ layer possesses high sensitivity in the near infrared region of spectrum, which needs attention to many environmental and security applications and offers more accurate and highly reproducible measurements. In addition, the sensitivity of the SPR based fiber optic sensor decreases with the increase in the thickness of In₂O₃ layer. With sensitivity as high as 4600 nm/RIU, the 170 nm thick In₂O₃ layer based fiber optic SPR sensor demonstrates better performance.