Phase-shift interferometry combined with surface plasmon resonance effect for two-dimensional bio-surface analysis

The phase-shift interferometry combined with surface plasmon resonance (SPR) effect has been studied as a novel technique used to analyze the bio-surface, which measures the spatial phase variation of SPR reflected light. The spatial sensitivity of the SPR imaging sensor is improved over the conventional SPR imaging systems based on optical intensity.     

Bimetallic Silver–Gold Film Waveguide Surface Plasmon Resonance Sensor

Abstract

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver–gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Integrated Si‐based nanoplasmonic sensor with phase‐sensitive angular interrogation

This work is related to the development of an integrated Surface Plasmon Resonance (SPR) sensor on silicon platform. The optical properties of metallic nanogratings fabricated on the semiconductor structure allow direct plasmonic detection in transmission mode. Specially designed angular interrogation method provides a periodic signal with phase dependent on the conditions of surface plasmon excitation. Proposed technique leads to sensitivity better than 10^?6 RIU for conventional SPR Kretschmann configuration and was tested on the integrated Si‐based nanoplasmonic chip. Developed concept is promising for low‐cost mono and multi ‐sensing applications by portable or stationary platforms.     

Temperature Effects on Prism-Based Surface Plasmon Resonance Sensor

We theoretically analyse the temperature effects on a surface plasmon resonance （SPR） sensor in Kretschmann configuration. The temperature effects include the thermo-optic effect and the dispersion of thermal-optic coefficient in the dielectric along with the thermal expansion effect, phonon-electron scattering and electron-electron scattering in the metal layer. We simulate the temperature dependence of the resonance position and the sensitivity of the SPR sensor under wavelength-interrogation and angular-interrogation mode of operation and the differences are pointed out in the two modes.     

表面等离子共振金/钯复合膜氢敏传感器

提出了一种新颖的钯(Pd)/金(Au)复合膜表面等离子共振氢敏结构,与单一Pd膜氢敏传感器相比,具有可靠性好、灵敏度高和响应度大等特点。利用表面等离子共振理论建立了Au/Pd复合膜氢敏传感器的数学模型,并对Au/Pd复合膜氢敏传感器的灵敏度进行了数值模拟。数值模拟结果表明:基于Au(2nm)/Pd(20nm)复合膜氢敏传感器所获得的最佳灵敏度比单一Pd(20nm)膜氢敏传感器提高了49 4%。     

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.     

Magnetized SPR sensor for enhanced functionality

It is known that a magnetic field changes the RI and the SPR angle of specific analytes. We have applied an external magnetic field to a surface plasmon resonance (SPR) sensor to exploit this phenomenon. A gold film is used for excitation of SPR in the sensor with a Kretschmann configuration. According to the concentration of 4-type analyte, we observed unique changes of the SPR angle due to the magnetic field, providing better classification of material type than a conventional SPR sensor.     

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.     

Bimetallic Silver-Gold Film Waveguide Surface Plasmon Resonance Sensor

It is desirable that a surface plasmon resonance (SPR) sensor is highly sensitive to binding interactions within the sensing region, generate evanescent fields with long penetration depths, and utilize a metal film that is very stable even in extreme environmental conditions. In this study, we present the first example of a wavelength-modulated waveguide SPR sensor with a bimetallic silver-gold film for surface plasmon excitation. The underlying silver yields better evanescent field enhancement of the sensing surface, while the overlying gold ensures that the stability of the metallic film is not compromised. It is shown experimentally that in terms of dλ/dn, the bimetallic film waveguide SPR configuration has a sensitivity of 1232 nm/RIU, greater than two times improvement from the 594 nm/RIU achievable with single gold film waveguide SPR sensor. The higher sensitivity, compact nature, and better evanescent field enhancement of this configuration provides the potential to biosensing applications.     

Characteristics of light emission from surface plasmons based on rectangular silver gratings

We investigated the characteristics of transmitted light from propagating surface plasmons based on rectangular silver gratings. The results calculated by rigorous coupled-wave analysis presented that silver diffraction gratings can produce significant transmittance and conversion efficiency, comparable to the case of dielectric gratings. Especially, silver gratings optimized at a wide range of grating thickness and period may lead to an improved diffraction efficiency larger than 64%. Moreover, the effect of silver oxide layer on the transmittance was examined and a bimetallic structure with a thin gold coating was introduced to prevent an oxidation of silver substrates. As a practical sensor application, silver grating-based surface plasmon resonance (SPR) configuration showed an enhanced sensitivity associated with an increase of surface reaction area and strong excitations of local plasmon fields, outperforming a conventional thin-film-based SPR structure.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Enhanced surface plasmon resonance imaging detection of DNA hybridization on periodic gold nanoposts

We explore periodic gold nanoposts as substrates for the enhanced surface plasmon resonance imaging (SPRi) detection of DNA hybridization. Rigorous coupled-wave analysis was used to model and design the nanopost-based SPRi biosensor. Arrayed gold nanoposts on gold-coated glass substrate, with various widths and periodicity, were fabricated using electron-beam lithography and characterized with scanning electron and atomic force microscopy. A scanning-angle SPRi apparatus was used to conduct the kinetic analysis of DNA hybridization on nanopost-based sensor surface and assess the corresponding SPR signal amplification. Experimental results showed that both the nanostructure size and period influenced the SPR signal enhancement; the optimized 30 nm height, 50 nm size, and 110 nm period nanoposts provided a fivefold SPR signal amplification compared with the plain 50 nm thick gold film used as control.     

内置调制层型光纤表面等离子体波共振传感器研究

研究了一种基于内置调制层结构的光纤表面等离子体波共振(SPR)传感器。通过在金膜与纤芯的内侧增覆具有不同厚度和属性的光学透明薄膜作为内调制层,构成了性能独特的光电复合薄膜,起到调节倏逝波矢量和金膜表面等离子体振荡波矢量的双重作用,进而控制共振效应,为调节灵敏度提供依据。采用时域有限差分方法对内置调制层结构光纤SPR共振激励模型属性进行数值仿真。在此基础上,研制了用于液体折射率测量的内置调制层型光纤SPR传感探针。实验结果表明,该传感器在1.335～1.392折射率范围内,随着待测液体折射率的增大,SPR共振光谱向长波方向偏移,且灵敏度达到2263.1nm/RIU,与基于纤芯-金膜-环境介质三层结构的常规光纤SPR传感器相比提高一倍,能够更好地满足环境折射率检测的需求。     

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.     

Surface plasmon resonance sensor based on diffraction grating with high sensitivity and high resolution

A surface plasmon resonance (SPR) sensor based on diffraction grating with high sensitivity and high resolution is proposed. The sensitivity of grating coupled SPR sensor based on angular interrogation is enhanced by replacing +1st diffraction order of metallic grating with −1st diffraction order to excite the surface plasmon. To improve the resolution of grating-based SPR sensor, aluminum is used as an SPR-active metal. The reflectivity dip of the Al-based sensor is sharper than an Au-based one, which is the mostly widely used as SPR-active metal. And 3-nm-thick gold film is deposited on the grating surface in order to protect the Al layer from getting oxidized. Numerical simulations show that the sensor not only has high sensitivity and high resolution, but also exhibits good linearity.     

Design of a highly sensitive surface plasmon resonance sensor using aluminum-based diffraction grating

A highly-sensitive grating-based surface plasmon resonance (SPR) sensor is proposed. The angular interrogation method has been used to study the performance of the sensor, and high sensitivity is obtained if the ?1st diffraction order is used to excite surface plasmon (SP). The sensitivity as well as the width of the SPR curves and reflective amplitude is considered for designing the sensor. Compared with the conventional gold (Au)-based or silver (Ag)-based SPR sensor, it is found that the aluminum (Al)-based sensor has the best performance. The oxidation problem of an Al-based SPR sensor has been addressed by coating it with an ultrathin gold film on the surface. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensitivity of the optimized sensor is 245°/RIU (degree per refractive index unit).     

Robustness of phase coherence against amplification in a flashlamp-pumped multi-pass femtosecond laser

We show that the phase of an ultra-short laser pulse undergoing the process of chirped-pulse amplification in a flashlamp-pumped multi-pass configuration is surprisingly well locked to the phase of the original pulse emitted by a mode-locked oscillator. We demonstrate that the relative phase jitter introduced in the amplification remains small (<0.1 rad r.m.s.) and does not spoil the visibility of fringes obtained in an interferometric experiment. These results indicate that, using a carrier-phase-stabilized seed laser, the generation of phase-controlled, high-intensity laser pulses is possible and relatively straightforward even with the commonly available flashlamp-pumped amplification systems. PACS 42.65.Re; 42.62.Eh; 42.25.Kb     

Surface profile measurement using laser-scanning angle deviation microscopy

Laser-scanning angular deviation microscopy based on the small angle measurement using surface plasmon resonance (SPR) phase detection technique is proposed. The phase shift coming from a SPR sensor is measured by a common-path heterodyne interferometry. This phase deviation is proportional to the beam converging or diverging angle, due to the specimen departing from the focal plane of objective lens. Using the phase deviations, one can calculate the surface profile by use of numerical method. The specimen could be scanned in real-time and the axial-resolution could be better than 1 nm. PACS 07.79-v; 68.37.-d; 73.20.Mf; 42.30.Wb; 42.62.Eh     

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.     

光纤SPR湿敏传感器及其共振光谱特性研究

提出并研制了基于光纤SPR传感探针的新型湿敏传感器。首先研究了光纤SPR传感探针对环境湿度变化的敏感特性,在此基础上提出在光纤SPR传感探针表面增覆不同厚度且具有水分子吸附功能的PVA薄膜来实现环境相对湿度的监测。研究结果表明,增覆双层PVA薄膜的光纤SPR传感探针在高湿区具有较好监测效果,其共振强度对应的相对湿度测量灵敏度达到1.59%/%RH,较光纤SPR探针呈现显著提高。而增覆单层PVA薄膜的光纤SPR传感探针在高湿区共振波长对应的相对湿度监测灵敏度达到2.411nm/%RH。此外所提出的新型光纤SPR湿敏探针在PVA薄膜失效后经过特殊工艺处理仍可重复镀膜使用。