Resolution enhancement of a surface immersion microscope near the plasmon resonance

Resolution of a surface immersion microscope has been studied as a function of surface-plasmon-polariton frequency. Enhancement of resolution near the surface-plasmon resonance has been observed. This effect may potentially be used in direct imaging of biological samples in liquid ambient.     

Localized surface plasmon resonance of silicon compounds adsorbed on silver nanoparticles

A simple method to produce silver nanoparticles on a glass surface from silver nanolayer deposited by magnetron sputtering and thermal annealed is presented. Localized surface plasmon resonance of nanoparticles shows a red shift depending on the silver nanolayer thickness, the refractive index and the thickness of an ultra-thin silicon compound adsorbed on the surface. A highly enhanced Raman spectrum of the characteristic groups of a silicon compound adsorbed on the nanoparticles surface was obtained.     

Sensitivity enhancement based on application of multi-pass interferometry in phase-sensitive surface plasmon resonance biosensor

A novel design of multi-pass surface plasmon resonance (SPR) biosensor with differential phase interrogation based on multi-pass interferometry is presented. This new configuration provides an intrinsic phase amplification effect of over twofold by placing the SPR sensor head in a signal arm of the interferometer so that the interrogating optical beam will traverse the sensor surface infinite number of times. Experimental interferometers based on the Michelson and Fabry–Perot configurations have been employed to experimentally verify this amplification effect when they were compared with Mach–Zehnder configuration, results obtained from salt–water mixtures, antibody–antigen, and protein–DNA binding reaction confirmed the expected phase measurement enhancement, thus leading to the possibility of direct detection of small sized bio-molecules using SPR.     

Sensitivity enhancement of graphene coated surface plasmon resonance biosensor

In this paper, a highly sensitive surface plasmon resonance biosensor is presented using angular interrogation. Due to low sensitivity of conventional biosensor, graphene/two-dimensional transition metal are used in surface plasmon resonance biosensor to improve the sensitivity. Here, we propose a seven layer model of biosensor which shows by incorporating silicon layer in addition of transition metal dichalcogenides MoS₂ and graphene, the sensitivity of the proposed SPR biosensor can be greatly enhanced than the conventional gold film SPR sensors. It is observed that the highest sensitivity can be obtained by optimizing the structure with 8 nm thickness of silicon layer, one layer of MoS₂ and one layer of graphene. The highest sensitivity of our proposed sensor is 210°/RIU.     

Scanning electro-optic microscope based on surface plasmon resonance

An optical scanning probe microscope, based on surface plasmon resonance (SPR) in the attenuated total reflection geometry, is shown to successfully image the polarization structures in self-assembled monolayers of hemicyanine adsorbed on a gold surface. Application of an ac field to the tip gives rise to the linear electro-optic effect in the monolayer just below the tip and the local change in the refractive index of the monolayer was detected via the ac component of the reflected light intensity, in which SPR-based detection intensifies the ac component. Polarization structures in a monolayer can be clearly imaged by this technique.     

表面等离激元的聚焦与波导增强

近年来,表面等离激元学（plasmonics）已经形成一个新的学科热点.电子在金属与介质界面的集体振荡行为形成一种元激发——表面等离激元（surface plasomon polariton,SPP）.由于其具有特殊的耦合与传播性质,与SPP相关的器件设计与应用成为目前纳米光子学领域的国际前沿研究方向.文章介绍了利用微...     

表面等离激元的聚焦与波导增强

近年来,表面等离激元学(plasmonics)已经形成一个新的学科热点.电子在金属与介质界面的集体振荡行为形成一种元激发——表面等离激元（surface plasomon polariton,SPP）.由于其具有特殊的耦合与传播性质,与SPP相关的器件设计与应用成为目前纳米光子学领域的国际前沿研究方向.文章介绍了利用微纳加工技术制备的SPP纳米结构,以及利用近场光学表征手段对SPP聚焦、波导、共振增强现象研究的进展.     

新型强度检测型表面等离子共振传感器的研究

针对角度检测型表面等离子共振传感器结构复杂,不易于实现在线测量的特点,基于表面等离子共振(SPR)原理,提出了采用双LED进行差分光强检测折射率变化的方法。设计了参考光路,可以消除光源波动带来的影响。理论分析及实验表明,这种方法比单LED光强检测方法的灵敏度提高了近1倍。由于没有使用角度检测装置及光谱仪,易于实现仪器的小型化。     

Influence of groove depth and surface profile on fluorescence enhancement by grating-coupled surface plasmon resonance

The fluorescence intensity of a sample placed on a metal grating pattern is enhanced due to excitation by the electric field of the grating-coupled surface plasmon resonance (GC-SPR). The dependence of the enhancement on groove depth and surface profile was studied with the aim of improving the sensitivity of fluorescence detection. The enhancement was found to depend on the groove depth, with intensity most enhanced on grating substrate of about 20 nm depth, which produced an intensity about 30 times greater than that on a flat borosilicate glass substrate. Rigorous coupled wave analysis calculation showed that the shape of the groove influenced GC-SPR, suggesting that controlling not only the depth but also the shape of the grating surface profile can be an important factor in improving the sensitivity of detection by fluorescence microscopy.     

Figure-of-merit enhancement of surface plasmon resonance sensors in the spectral interrogation

We show that adding a thin dielectric layer with high refractive index on top of the metallic layer in surface plasmon resonance sensors in the Kretschmann-Raether configuration in the spectral mode causes a redshift of the resonance wavelength, narrowing of the resonance dip, and an enhancement to the spectral sensitivity. Surprisingly, together with the sensitivity enhancement, the dip becomes much narrower and the figure of merit is considerably improved, particularly in the IR range.     

基于计算机软件的新型SPR传感器设计

为了改进SPR传感器灵敏度低、稳定性差、测量范围窄等问题,基于光的衰减全反射理论设计了一种SPR传感装置。利用FDTD计算机软件分析得到:设计的结构分子层和金属薄膜之间的界面磁场强度得到极大地提高,测量精度有了显著的改进;很大一部分倏逝场能量集中在表面等离子共振区,倏逝波的强度非常强。     

LED based fiber optic surface plasmon resonance sensor

Modeling of a miniaturized fiber optic sensor based on surface plasmon resonance utilizing a broad band diffuse source is presented. Attenuated total internal reflection with Kretschmann configuration is the basis of the theoretical model. For simulation both meridional and skew rays are considered. The performance of the sensor is evaluated in terms of sensitivity, detection accuracy and signal to noise ratio. Effects of the numerical aperture of the fiber, core diameter and length of the sensing region on the performance parameters of the sensor are studied. The results are obtained for gold and silver metallic layer on the core of the fiber. The theoretical results obtained are compared with SPR based fiber optic sensor utilizing focused beam on the end face of the fiber from a collimated source. The advantages of using broadband LED (diffuse source) source for launching light in the fiber are the miniaturization, compactness and low cost of the sensor.     

Sensitivity enhancement of surface plasmon resonance sensor using continuous film metallic gratings

A surface plasmon resonance (SPR) sensor based on continuous film metallic gratings is numerically investigated for enhance sensitivity. The results calculated by rigorous coupled-wave analysis (RCWA) present that interplays between localized surface plasmons and surface plasmons polaritons contribute to sensitivity enhancement. The sensitivity enhancement factor (SEF), which represents the influence of metallic grating, increased as the grating period decreased. In addition, several reflection dips can be achieved as the period of metallic grating increased. By double-dips method, the sensitivity SPR sensor based on continuous film grating-based is improved into 153.23°/RIU, which is more sensitive than conventional thin film-based SPR sensor in the same condition. The SPR sensor based on continuous film metallic gratings exhibits good linearity.     

金属表面等离体子振荡

深入浅出地分析了金属表面等离体子振荡形成的机理，利用拉普拉斯方程得到了半无限金属、金属薄膜和球状纳米金属颗粒的表面等离体子振荡频率。     

Quantum surface plasmon resonance system based on electromagnetically induced transparency

A scheme for a new kind of surface plasmon resonance system (SPR) is proposed. The system is composed of three layers: a prism, a thin metal film, and a hybrid dielectric consisting of EIT atoms and a background substance. It is found that due to the inherently quantum feature, the EIT-based SPR system exhibits some interesting quantum properties which are absent in ordinary SPR systems. This system may be used for detecting very small variations of quantum properties of matters, such as small shifts of atomic levels caused by external fields, with subwavelength spatial resolution.     

基于辅助电介质层的棱镜表面等离子体共振效应研究

研究了一种基于棱镜基底-辅助电介质层-金膜-待测介质四层结构的表面等离子体共振(surface plasmon resonance,SPR)效应激励模型.采用薄膜光学与波导理论,探索了由辅助电介质层与金膜复合而成共振薄膜对SPR效应的激励机理与调制特性.借助时域有限差分方法,数值模拟得到辅助电介质层属性与共振能量传输特性关系.在此基础上,构建了波长调制型棱镜辅助电介质层结构SPR激励系统.研究结果表明,当待测介质折射率相同时,相较基于棱镜基底-金膜-待测介质三层结构的Kretschmann激励模型,辅助电介质层激励模型共振光谱整体向长波方向偏移且半波宽度出现显著展宽效应.而当待测介质折射率增大时,辅助电介质层型激励模型的共振光谱不仅会向长波方向偏移,而且折射率响应灵敏度比棱镜Kretschmann三层激励模型高出75%.因此该模型能够为诸如高灵敏度检测、新型光学滤波与调制器件设计等领域的研究应用提供理论与实践储备.     

Design of terahertz beam splitter based on surface plasmon resonance transition

According to the resonance transition between propagating surface plasmon and localized surface plasmon, we demonstrate a design of beam splitter that can split terahertz wave beams in a relatively broad frequency range. The transmission properties of the beam splitter are analyzed utilizing the finite element method. The resonance transition between two kinds of plasmons can be explained by a model of coherent electron cloud displacement.     

Measurement of small displacement based on surface plasmon resonance heterodyne interferometry

This paper proposes an optical method for measuring small displacements using the surface plasmon resonance (SPR) heterodyne interferometry. A heterodyne light beam reflected by a mirror passes through a hemisphere glass and then enters into a surface plasmon resonance apparatus at the resonant angle. A small displacement of the mirror will introduce a phase-difference variation between p- and s-polarizations of the light emerging from the SPR apparatus. The phase-difference variation can be precisely measured with the heterodyne interferometric technique, and the associated displacement can be estimated. The feasibility of this method was verified by experiment, and the displacement measurement resolution of about 1.4 nm over a traveling range of 6 μm was achieved. Our method of measurement has the merits of both common-path interferometry and heterodyne interferometry.