差分式强度检测型表面等离子共振传感器的研究

针对表面等离子共振(SPR)传感器需要昂贵的角度转动或光谱分析装置的缺点,提出了采用双LD进行差分光强检测折射率变化的方法.该方法基于等离子共振原理,采用两个波长对应的反射光强差来实现对介质折射率变化量的传感,设计了参考光路,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LD光强检测方法的灵敏度提高了近一倍.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.可通过调整入射角和采用不同光源的方法来实现不同区间的折射率测量.     

双光束双曝光与四光束单曝光干涉光刻方法的比较

双光束双曝光和四光束单曝光是无掩模激光干涉光刻的两种典型方法,都容易利用现有光刻工艺,在不需掩模和高精度光刻物镜的情况下,用简单廉价光学系统在大视场和深曝光场内形成孔阵、点阵或锥阵等周期性图形。双光束双曝光法得到的阵列图形周期极限为λ/2;四光束单曝光的周期略大,为前者的2倍。模拟和实验结果表明,通过控制曝光和显影工艺,双光束双曝光较四光束单曝光能更灵活地得到孔阵或点阵,而四光束单曝光得到的图形孔与孔之间没有鞍点,较双光束双曝光形成的孔侧壁更陡。这两种方法在需要在大面积范围内形成孔或点这类周期阵列图形的微电子和光电子器件的制造领域有很好的应用前景。     

双光束光电二极管阵列检测器的设计

由于普通光电二极管阵列检测器无法克服光源波动造成的影响,故设计开发了一种双光束光电二极管阵列检测器。该检测器采用光导纤维束将光源发出的光分成两束,在斩光器的调制下分时射入样品吸收池和参比吸收池。透射出的光信号通过光导纤维束射到狭缝上,被凹面光栅分光成像于光电二极管阵列上。在斩光器和后续电路的配合下,实现了在同一个光电二极管阵列上信号光光谱、参考光光谱和暗电流的分时测量。由于采用参考光光谱和光电二极管阵列暗电流对信号光谱进行实时补偿,可以使基线短期噪声降低为1×10-5AU,漂移降低为1×10-4AU/h。     

Eu：Fe：LiNbO3晶体双光束耦合异常现象的研究

在Ｅｕ：Ｆｅ：ＬｉＮｂＯ３晶体的双光束耦合实验中，减小晶体厚度，增大泵浦光束直径，都可使指数增益系数和衍射效率增大，２θ角度响应范围加宽。升高温度亦可增大衍射效率。本文对上述实验结果进行了理论分析。     

双光束补偿扫描系统

提出一种新的高精度大型平面扫描仪。利用双光束补偿系统，扫描头由一特殊光路组成。当入射光通过此光路后，产生对称输出的两束光。当入射光发生角漂或扫描头发生摆动时，输出的两束光对称上下漂移，其中心线保持不变，故扫描形成的基准面保持不变，从而大大提高了测量精度。经实验证明，测量精度优于2．5×10－6。     

双光束镀膜系统中的信号优化处理研究

为提高光电极值法膜厚监控质量,对微弱光电探测信号设计一套优化的电路处理和数字处理系统。基于双光束镀膜监控思想,提出三级模拟放大电路、双锁相对称放大电路、综合抗干扰技术、数字除法、防脉冲干扰数字滤波、数码显示线性化、剔除奇异数据和ΔR值极值判断等信号综合处理方案。实验表明:电路的测试路输出和参考路输出信噪比均大于500,漂移率≤7%/h;数码显示对反射率响应的灵敏度在整个反射率范围内均比较大,数码显示值的线性回归系数为0.979,低反射率膜的反射率显示分辨极限为0.02%;镀膜中极值点监控信号的不确定度至少比通用系统降低1个数量级,漂移率接近于0。采用此方案对微弱膜厚信号的高精度、高稳定性检测大大提高了膜厚监控系统的静态、动态稳定性和膜厚控制精度,膜厚控制的标准偏差为0.55%。     

表面等离子共振氢敏传感器理论和模拟

提出了一种钯(Pd)膜氢敏感表面等离子共振传感器结构,该传感器以镀在棱镜端面的 Pd作为氢敏感膜。Pd 膜吸氢以后发生化学反应,生成的 PdHx使折射率发生变化,同时,它作为金属膜产生 SPW,当折射率变化时又在金属和介质表面产生表面等离子共振。利用 Fortran 语言程序进行了表面等离子共振氢敏传感器的 Pd 膜厚度和传感器灵敏度数值模拟。氢气浓度的变化引起折射率的变化,数值模拟表明,表面等离子共振氢敏传感器的灵敏度与 Pd 膜厚度有关,当 Pd膜的厚度在 10-30nm 时,氢气浓度在 1%-10%范围内具有较高的灵敏度。这种传感器结构将用于监测氢气作燃料的商用和军用机车的氢气泄漏。     

多面转镜双光束扫描场的研究

运用矢量光学理论研究了双光束多面转镜扫描场中的相应问题：导出双光束扫描的基本方程,其中包括,入射点集团,反射点在空间以及在转镜反射面的移动轨迹,反射线标量方程,观察面上扫描点的集团以及远场扫描轨迹等,这些方程描述了多光束面转镜扫描的动态特性及其基本规律;在此基础上通过数值计算分析研究扫描场的成象特性。     

激光器光束质量测量技术研究

由于半导体激光器结构的特点,在其应用中需对其波束进行整形,为了有利于大功率半导体激光器的推广应用,需准确识别大功率半导体激光器的输出分布特性。该文从M2因子、远端发散角,近端及远端的光强分布等方面对大功率半导体激光器的光束质量进行了测量技术研究,给出了相应的测量方案和误差分析。     

差分表面等离激元共振传感仿真研究

从薄膜光学理论出发,对不同金属膜厚度、不同实折射率和不同复介电常数的环境介质的表面等离激元共振(SPR,Surface Plasmon Resonance)信号进行了分析,给出了最佳金属膜厚度,并且,折射率与共振角呈线性关系(R=0.999 4).分析了采用差分处理时,随环境介质的复介电常数变化的光反射率曲线.结果表明,同组两个探测器信号的和随环境介电常数的虚部变化,与实部无关,其信号差则相反,因此,能够同时测量环境介质的介电常数的实部和虚部.     

Numerical investigation of a grating and graphene-based multilayer surface plasmon resonance biosensor

A multilayer surface plasmon resonance biosensor (SPRB) incorporating a grating-graphene configuration is investigated for enhanced sensitivity. The numerical analysis of the impact of integrating a periodic array of subwavelength grating on top of a layer of graphene sheet for improving sensitivity is presented. The result of monitoring the biomolecular interactions of DNA hybridization is compared against the outcome of the conventional SPRB, a graphene-based multilayer SPRB, and a multilayer layer grating SPRB, and is mathematically validated. It is demonstrated that the inclusion of a grating and graphene layer on top of the gold thin film is an excellent candidate for a highly sensitive SPRB. To achieve further enhancement of sensitivity, the subwavelength grating is numerically optimized against its geometry including grating configurations (rectangular, sinusoidal, and triangular), grating depth, volume factor, and grating period.     

Analysis of biomolecular interactions using a miniaturized surface plasmon resonance sensor

A commercially available miniaturized surface plasmon resonance sensor has been investigated for its applicability to biological interaction analysis. The sensor was found to exhibit excellent repeatability and linearity for high-refractive index solutions and good reproducibility for the binding of proteins. Its detection limit for the monoclonal antibody M1 was found to be 2.1 fmol, which corresponds to a surface concentration of 21 pg/mm2. Simple surface immobilization procedures relying on biotin/avidin or glycoprotein/lectin chemistry have been explored. Equilibrium dissociation constants for the binding of the FLAG peptide to its monoclonal antibody (M1) and for the binding of concanavalin A to a glycoprotein have been determined. The close agreement of these measurements with values obtained by surface fluorescence microscopy and fluorescence correlation spectroscopy helps to validate the use of this device. Thus, this sensor shows promise as an inexpensive, portable, and accurate tool for bioanalytical applications in laboratory and clinical settings.     

Fabrication and simulation studies on D-shaped optical fiber sensor via surface plasmon resonance

This paper describes simulation and experimental methods for designing a D-shaped surface plasmon resonance (SPR) fibre sensor. The sensor consists of two set-up approaches. Finite element method is used in simulation on the fibre sensor device. Two experimental methods for detecting relative intensity are used by varying the wavelength of the optical signal sources and the thickness of gold layer coated on the D-shaped fibre. In the first method, the sensor device works by detecting the relative intensity of two optical signal sources having different wavelengths. In the second set-up, the relative intensity between two D-shaped fibres coated with different thicknesses of gold is measured when a single signal source is launched at the input. The difference in intensities of the signal outputs is used to estimate the refractive index at the sensing region. A prototype SPR D-shaped fibre sensor has been fabricated and the experimental results show good agreement with simulation.     

Hybrid surface platform for the simultaneous detection of proteins and DNAs using a surface plasmon resonance imaging sensor

In this work, we present a novel surface and assay for the simultaneous detection of DNA and protein analytes on a surface plasmon resonance (SPR) imaging sensor. A mixed DNA/oligo (ethylene glycol) (OEG) self-assembled monolayer (SAM) is created using a microarrayer. Thiol-modified single-stranded DNA sequences are spotted onto a gold-coated glass substrate. Backfilling with an OEG-modified alkanethiol creates a protein-resistant surface background. Antibodies conjugated to complementary single-stranded DNA sequences are immobilized on the surface through DNA hybridization. By converting only part of the DNA array into a protein array, simultaneous detections of DNA and protein analytes are possible. A model system of two cDNA sequences and two human pregnancy hormones are used to demonstrate the assay. No cross-reactivity was observed between DNA or protein analytes and nontargeted immobilized cDNA sequence or antibodies. A response from a detection of a single analyte in a mixture of protein and DNA analytes corresponds well with that of a single-analyte solution.     

Analysis of a highly birefringent asymmetric photonic crystal fibre based on a surface plasmon resonance sensor

Abstract

A highly birefringent photonic crystal fibre is proposed and characterized based on a surface plasmon resonance sensor. The birefringence of the sensor is numerically analyzed by the finite-element method. In the numerical simulation, the resonance wavelength can be directly positioned at this birefringence abrupt change point and the depth of the abrupt change of birefringence reflects the intensity of excited surface plasmon. Consequently, the novel approach can accurately locate the resonance peak of the system without analyzing the loss spectrum. Simulated average sensitivity is as high as 1131 nm/RIU, corresponding to a resolution of 1 × 10^?4 RIU in this sensor. Therefore, results obtained via the approach not only show polarization independence and less noble metal consumption, but also reveal better performance in terms of accuracy and computation efficiency.     

Etched glass microarrays with differential resonance for enhanced contrast and sensitivity of surface plasmon resonance imaging analysis

We report the fabrication and characterization of gold-coated etched glass array substrates for surface plasmon resonance imaging (SPRi) analysis with significantly enhanced performance, in particular image contrast and sensitivity. The etching of the glass substrate induces a variation in the resonance condition and thus in the resonance angle between the etched wells and the surrounding area, leading to the isolation of the array spot resonance with a significant reduction of the background signal. FDTD simulations show arrays with large spots and minimal spot-to-spot spacing yield ideal differential resonance conditions, which are verified by experimental results. Simulations also indicate the etched well structure exhibits enhanced SPR electric field intensity by 3-fold as compared to standard planar gold chips. Changes in the bulk sensitivity of the etched arrays have been obtained at the 10(-4) RIU level based on image intensity difference. The strong image contrast allows for improved microarray imaging analysis with easily distinguished signals from background resonance. The etched array chips are demonstrated for SPRi detection of bacterial toxins through the coating of an ultrathin SiO(2) film for direct vesicle fusion that establishes a supported membrane-based biosensing interface. Protein detection with cholera toxin (CT) at 5 nM is obtained, making this chip one of the most sensitive SPR imaging substrates ever reported without a postbinding amplification scheme. Furthermore, the surface can be regenerated by Triton X-100 for repeated cycles of membrane formation, protein binding, and biomolecular removal. The reusability and enhanced performance of the etched glass array chips should find a broad range of applications, opening up new avenues for high-throughput SPR imaging detection with convenience and marked surface sensitivity.     

Characterization and optimization of a real-time, parallel, label-free, polypyrrole-based DNA sensor by surface plasmon resonance imaging

We describe in this paper a methodology to quantify multispot parallel DNA hybridizations and denaturations on gold surfaces by using, on one hand, a polypyrrole-based surface functionalization based on an electrospotting process and, on the other hand, surface plasmon resonance imaging allowing real-time measurements on several DNA spots at a time. Two characterization steps were performed in order to optimize the immobilization of oligonucleotide probes and, thus, to increase the signal-to-noise ratio of monitored hybridization signals: the first step consisted of characterizing the signal dependence upon the density of immobilized 15-mer probes, and, the second step, in analyzing the hybridization response versus spot thickness. We further demonstrated that a surface density of polypyrrole/DNA probes of approximately 130 fmol/ mm2 (590 pg/mm2) optimizes the hybridization signal that can be detected directly. Optimal thickness of the spot was found to be close to 11 nm. Specificity and regeneration steps on each spot have also been demonstrated successfully, showing this method to be very competitive and convenient in use.     

Concentration detection of quantum dots in the visible and near-infrared range based on surface plasmon resonance sensor

We employ an optical sensor based on surface plasmon resonance (SPR) operating in the near-infrared and in the visible range to determine the concentration of CdSe/ZnS core-shell quantum dots (QDs) which are embedded in the SU8 organic films. Attenuated total reflection (ATR) measurements show that the amplitude of the shift of the resonance dip is closely related to the concentration variation of QDs in the organic films and the incident laser. The sensitivity is enhanced by 1.5-time and the detect limitation is expanded to 10⁻⁵ μmol/L in the visible range as compared to that in the near-infrared. The sensitivity enhancement and the expansion of detect limitation of the visible SPR sensor may originate from the coupling of surface plasmons to luminescence from QDs.