Enhancement of the resolution of surface plasmon resonance biosensors by control of the size and distribution of nanoparticles

A new resolution-enhanced surface plasmon resonance (SPR) biosensor offers a tenfold improvement in resolution compared with conventional SPR biosensors in the detection of the surface coverage of biomaterials. The proposed optical biosensor, based on the attenuated total-reflection method, excites both the surface plasmons and particle plasmons to enhance the local electromagnetic field by control of the size and volume fraction of embedded Au nanoparticles to increase the resolution of the device. The SPR biosensor design is based on the Maxwell-Garnett model and the Fresnel equations, and the device is fabricated with a cosputtering deposition system.     

基于光谱解调的对称波导型表面等离子体共振传感研究

表面等离子体共振(SPR)传感系统有角度谱、光谱、强度、相位等解调方式,其中光谱型的(SPR)传感系统因可以使用光纤导光,将传感部分独立出来,可进行远距离传感和现场检测,并能有效缩小系统的体积。对称光波导型(SOW)SPR因金属膜层两边的折射率完全相同,表面等离子体波传播距离更长,穿透深度更深,比传统的SPR系统具有更高的灵敏度和分辨率。对对称波导型(SOW)SPR进行光谱解调研究,以MgF₂-Au-MgF₂结构的SOW-SPR为传感单元,同时以光纤输出的卤素灯为光源, 搭建了一套光谱解调的SOW-SPR检测系统,以不同浓度的葡萄糖溶液对系统折射率分辨率进行测量,得到2.8×10-7 RIU的分辨率。为SOW-SPR系统小型化、现场检测以及远距离探测提出一种可能实现的手段,具有很好的应用前景。     

Phase sensitive SPR sensor for wide dynamic range detection

Phase detection has been utilized to enhance the sensitivity of surface plasmon resonance (SPR) sensors for a long time. However, an inherent drawback for phase sensitive SPR sensors are their limited dynamic range, which has greatly hindered wide applications of such sensors. In this Letter, a design combining phase detection and angular interrogation has been proposed to provide an SPR sensor with both high sensitivity and wide dynamic range. As a result, a resolution of 2.2×10^-7?RIU with a dynamic range of over 0.06?RIU has been achieved simultaneously. An added advantage of this design is the flexibility for sensitivity and dynamic range adjustment.     

Surface plasmon resonance (SPR) reflectance imaging: Far-field recognition of near-field phenomena

The surface plasmon resonance (SPR) reflectance imaging technique provides a label-free visualization tool to characterize the near-field fluidic transport properties within 100 nm from the solid surface. The key idea is that the SPR reflectance intensity varies with the near-field refractive index (RI) of the test fluid, which in turn depends on the micro- and nano-fluidic scalar properties such as concentrations, temperatures, and phase changes, occurring in the near-field. As essential knowledge to understand and implement the SPR reflectance imaging technique, this paper presents discussions on the basics of surface plasmon polaritons (SPPs), surface plasmon resonance (SPR), setup of the SPR reflectance imaging system, and the SPR reflectance imaging resolution. The second part of the paper elaborates the applications of the SPR imaging sensor technique in characterizing the near-field fingerprints of nanofluidic evaporative self-assembly.     

基于全相位滤波技术的光纤表面等离子体共振传感解调算法

基于生物样品检测对折射率传感的迫切需求,构建一种全光纤表面等离子体共振(surface plasmon resonance,SPR)系统,并针对其设计了基于全相位滤波技术的SPR特征波长传感解调算法.基于系统仿真,理论计算了光纤SPR传感器的折射率传感灵敏度.采用全相位滤波技术提取光纤SPR传感器透射光谱的特征波长,理论推导了全相位滤波器的解析表达式.实验结果表明,使用本算法的光纤SPR传感器折射率传感灵敏度为1640.4 nm/RIU,折射率检测的分辨率是7.36×10~(-4)RIU,与传统方法相比,有效提高了系统的检测精度和抗光源扰动性能,降低了实验成本.     

Numerical study of a highly sensitive surface plasmon resonance sensor based on circular-lattice holey fiber

A new design of surface plasmon resonance (SPR) sensor employing circular-lattice holey fiber to achieve high-sensitivity detection is proposed. The sensing performance of the proposed sensor is numerically investigated and the results indicate that our proposed SPR sensor can be applied to the near-mid infrared detection. Moreover, the maximum wavelength sensitivity of our proposed sensor can reach as high as 1.76×10⁴ nm/refractive index unit (RIU) and the maximum wavelength interrogation resolution can be up to 5.68×10^-6 RIU when the refractive index (RI) of analyte lies in (1.31, 1.36). Thanks to its excellent sensing performance, our proposed SPR sensor will have great potential applications for biological analytes detection, food safety control, bio-molecules detection and so on.     

基于辐射度的光谱校正与自适应拟合相结合的SPR共振波长确定方法

表面等离子体共振(SPR)传感技术因其灵敏度高、无需标记、可原位实时监测的特点,被广泛应用在生物医学、化学检测、食品安全、环境监测等领域。对于波长调制型SPR传感器,由于光谱测量系统各部件对不同波长响应度不同,从而对光谱共振波长的实际位置产生干扰,影响到实验检测结果。为消除这种影响,提出了一种基于辐射度空间的SPR相对反射率校正方法,并使用阶数自适应拟合算法对共振波长进行精确测定。通过标定光谱测量系统的仪器响应曲线,将光谱仪得到的原始光谱转换成辐射光谱,进而计算出不依赖于光谱仪系统中任何部件的SPR相对反射率。相比于传统的反射率校正方式(以共振光谱除以非共振光谱的结果作为反射率光谱),此方法校正后的光谱在光谱形状上具备半峰宽更窄和共振峰更对称的优势,从而为精确确定共振波长提供了可靠的保障。随后基于拟合误差最小化的目标,对共振区域采用阶数自适应多项式拟合算法确定共振波长。实验测量了不同入射角度下的SPR共振光谱,使用此方法校正得到反射率光谱的半峰全宽保持在(100±10) nm,表明此方法的光谱峰形优势具备普适性;连续采集了4 000组光谱并计算共振波长,其相对标准偏差为0.007 8%,处理速度为每个光谱12 ms,表明此方法具备良好的抗噪声波动鲁棒性和光谱数据处理的实时性;测量了不同浓度下NaCl溶液的SPR共振光谱,其共振波长与溶液折射率线性相关系数为0.998 5,品质因数为传统校正方式的3倍,表明此方法具备良好的可靠性,并且从光谱的处理算法层面提高了传感性能,相比于从工艺制备上提高品质因数的传统方式,处理简便,效果更突出。结果表明,基于辐射度空间的相对反射率矫正与阶数自适应拟合相结合的SPR共振波长检测方法具备可靠性好、运算速度快、分辨率高、抗噪声、品质因数高等特点,能够有效提高SPR传感器的数据处理与传感性能。     

Common-path phase-shift interferometry surface plasmon resonance imaging system

Surface plasmon resonance (SPR) and common-path phase-shift interferometry (PSI) techniques are integrated in a biosensing imaging system for measuring the two-dimensional spatial phase variation caused by biomolecular interactions on a sensing chip without the need for additional labeling. The common-path PSI technique has the advantage of long-term stability, even when it is subjected to external disturbances. Hence the system meets the requirements of the real-time kinetic studies involved in biomolecular interaction analysis. The proposed SPR-PSI imaging system demonstrates a detection limit of a 2 x 10(-7) refractive-index change, a long-term phase stability of 2.5 x 10(-4) pi rms for 4 h, and a spatial phase resolution of 10(-3) pi with a lateral resolution of 100 microm.     

基于银膜孔阵列超强透射效应的相敏表面等离子体共振传感器的仿真研究

A high spatial resolution, phase-sensitive Surface Plasmon Resonance（SPR） sensor based on Extraordinary Optical Transmission （EOT） is proposed to monitor the binding of organic and biological molecules to the silver surface. The 2D nanohole-array configuration is well suited ~br dense integration in a sensor chip. The optical geomeWy is collinear, which simplifies the alignment with respect to the traditional Kretschmann arrangement for SPR sensing. Various design parameters of the device have been studied by simulation. The heterodyne technique is used to improve the sensitivity. The optimization results indicate that the sensor has the advantages of achieving high resolution and a wide dynamic range simuhaneously.     

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.     

Highly sensitive differential phase-sensitive surface plasmon resonance biosensor based on the Mach-Zehnder configuration

A high-sensitivity surface plasmon resonance (SPR) biosensor based on the Mach-Zehnder interferometer design is presented. The novel feature of the new design is the use of a Wollaston prism through which the phase quantities of the p and s polarizations are interrogated simultaneously. Since SPR affects only the p polarization, the signal due to the s polarization can be used as the reference. Consequently, the differential phase between the two polarizations allows us to eliminate all common-path phase noise while keeping the phase change caused by the SPR effect. Experimental results obtained from glycerin-water mixtures indicate that the sensitivity limit of our scheme is 5.5 x 10(-8) refractive-index units per 0.01 degrees phase change. To our knowledge, this is a significant improvement over previously obtained results when gold was used as the sensor surface. Such an improvement in the sensitivity limit should allow SPR biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence. Monitoring of the bovine serum albumin (BSA) binding reaction with BSA antibodies is also demonstrated.     

Focused cylindrical vector beam assisted microscopic pSPR biosensor with an ultra wide dynamic range

A novel phase-sensitive surface plasmon resonance (pSPR) biosensor based on differential phase measurement between two cylindrical vector beams, namely radially polarized and azmuthally polarized beams, is proposed and studied in an inverted microscope. Different from a fixed angle or a relatively small angular range for SPR excitation in the attenuated total reflection (ATR) configuration, the signal beam focused by a total internal reflection fluorescence microscopic objective contains the entire angular range from 0 to the maximum angle given by the numerical aperture, leading to a dynamic range of 0.41 RIU which is over seven times wider than the best result of the ATR pSPR sensor. Moreover, with the technique of differential phase measurement between radial and azimuthal polarizations employed in our configuration, high sensitivity of ±9.05×10(-8) refractive index unit/1 deg can simultaneously be achieved in principle. The proposed technique maintains the unique advantages in terms of securing high imaging resolution and sensitivity with an ultra-wide dynamic range simultaneously.     

适用于激光聚变实验的短焦距高放大倍率Wolter显微镜设计

围绕内爆压缩及阻滞阶段相关物理实验的诊断需求,提出了一种满足阿贝正弦条件的短焦距高放大倍率Wolter-Ⅲ型X射线显微镜的光学设计。详细介绍了Wolter-Ⅲ型显微镜的结构特点和设计方法,与Wolter-Ⅰ型相比可以通过将主平面向靠近物点方向移动的方式减小系统焦距,从而获得更大的放大倍数,实现显微镜与探测器的像质匹配,提高诊断系统的空间分辨。由光线追迹可以得出,在±190 μm的视场范围内,空间分辨率优于3 μm;在±240 μm范围内分辨率优于5 μm;在±300 μm范围内分辨率优于8 μm,几何集光立体角约为5×10?6 sr。     

大量程激光位移传感器的成像系统设计

为了解决目前国内自主研发的激光位移传感器基准工作距离短和测量范围小的问题,设计了一种适用于远距离测量的大量程激光位移传感器成像光学系统。基于激光三角测量原理,结合具体使用要求计算了大量程激光位移传感器的性能指标和成像光学系统的设计参数。选择5片式透镜结构作为系统的初始结构,利用光学设计软件对大量程激光位移传感器成像光学系统进行了仿真,完成了系统优化和性能分析,实现了基准工作距离为1 000 mm、量程为±500 mm、分辨率为0.4 mm的大量程激光位移传感器成像系统设计。结果表明,在测量范围±500 mm内,系统均可以满足成像质量要求。该激光位移传感器成像系统具有工作距离远、测量量程大、结构简单的特点,可满足1 000 mm远距离处大量程范围的测量使用要求。     

Design of a silicon-based plasmonic optical sensor for magnetic field monitoring in the infrared

Surface plasmon resonance (SPR) sensor chip is proposed for magnetic field monitoring in the infrared wavelength region. The structure is based on silicon substrate and gold as SPR-active metal used with an appropriate magnetic fluid film. The angular interrogation method has been used to study the sensor’s performance in terms of large shift and small width of the SPR curve for a wide range of magnetic field between 30 and 220 Oe. The effect of field incidence angle is also studied on the proposed sensor’s performance, and it is observed that the field should be incident as parallel to the magnetic fluid surface as possible. Any possibility of oxidation problem to the proposed SPR sensor is addressed by using a stable buffer layer. All the performance parameters were found to be significantly large for the above field incidence condition. The proposed sensor is able to achieve a resolution of the order as high as 0.18 Oe for magnetic field detection.     

契形结构光纤表面等离子体共振传感器研究

提出了一种契形端面结构的光纤表面等离子体共振(SPR)传感器激励模型. 采用时域有限差分法对契形SPR波导的共振模型进行数值模拟, 通过在光纤出射端抛磨契形角度并进行敏感膜修饰, 制出具有契形端面结构的类Kretschmann微棱镜式光纤SPR传感器, 实现激发SPR的光波调制.结果表明, 在1.3330–1.4215折射率范围内, 制备的契形光纤SPR传感器相对于常规光纤SPR传感器, 其平均灵敏度提高了近1–6倍, 1倍和6倍分别出现在小角度结构(15° 契形) 传感器和大角度结构(60°契形) 传感器, 且仍保持 10^-5 等级的分辨率. 该类型结构的传感器具有契形端面激励模式, 设计灵活性高、制备工艺简单、可微量检测样本等优点, 能够很好地适应于不同环境和测量条件的实际生化检测、环境监测需求. 关键词： 光纤传感器 表面等离子体共振 契形端面结构 折射率灵敏度     

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.     

BEPC Ⅱ注入器相控系统的设计

 以2.856GHz频率上相位控制达到±2°为目标，阐述北京正负电子对撞机重大改造工程注入器相控系统设计思路，提出相应的系统实现结构。在分析相控过程的基础上，分解系统指标，把它作为相控系统详细设计和关键部件测试的依据。最后，针对相位测量这一关键问题，给出了具体的实现方法。     

用场分析法求解速调管输出回路特性参数

 为解决速调管输出回路特性参数计算时遇到的困难，结合场分析的手段和3维电磁场模拟计算软件ISFEL3D后处理部分，提出了场分析法。理论分析表明，场分析法可用于计算单注单间隙、多注单间隙、单注多间隙和多注多间隙等各种速调管输出回路的谐振频率、间隙阻抗实部和外观品质因数等特性参数。通过对单注单间隙速调管输出回路的举例计算表明，场分析法的计算结果与反射相位法和等效间隙阻抗法的计算结果吻合较好，初步证实了该方法的可操作性和理论推导的正确性。     

波前编码显微物镜景深扩展的研究

为了解决传统显微物镜景深与分辨率的矛盾,采用波前编码的方法,设计研究了波前编码的10倍显微物镜,结合传统光学设计软件,采用基于MTF一致性的相位板参数的优化方法,实现了在像面附近一定范围内系统的点扩散函数一致性;此外,还设计了扩展三次相位编码板的10倍显微物镜,比较了采用两种不同相位板系统的焦深扩展的效果,结果显示三次相位板的焦深扩展效果较好,可以将传统10倍显微物镜的焦深扩展15倍。成像模拟仿真结果显示滤波后的编码像在±15倍焦深范围内成像清晰,从而扩大了系统的景深。