采用光纤技术实现拉曼光谱和扫描隧道显微镜实时联用测试

设计并制作了与扫描隧道显微镜（ＳＴＭ）探头和拉曼光谱仪相适配的光纤探测装置，该装置采用配有不很短焦距的自聚焦透镜以获得较大的相对孔径，并使用多束光纤以充分利用扫描隧道显微镜探针周围有限空间，提高了拉曼散射光的收集效率，获得具有较高信噪比的拉曼谱图，在该装置的基础上进一步建立拉曼－扫描隧道显微镜联用系统，初步实验表明该联用系统用于实时研究固／气和固／液界面体系是可行的，即利用扫描隧道显微镜可获得固体     

用于接触式探测的多模光纤探针形状优化

对于进行接触式探测的多模光纤探针,信号光来自于附着于探针表面的待测物。基于几何光学,提出了一个物理模型,用以分析探头形状对所收集的信号光强度的影响。采用此模型,对抛物线型探头进行了仿真,给出了最优形状参数,并采用表面增强拉曼探针进行了初步实验验证。此分析可用于指导各种光纤传感器的设计,以确定其最佳的形状参数,适用于荧光传感器、表面等离子体共振传感器、表面增强拉曼传感器等。     

超细低水峰抗弯损光纤的设计及制作

采用全合成预制棒制造法（VAD＋OVD）和改进的G.652.D光纤拉制法制造光纤.研究了工艺中光纤芯径的大小、第一包层的厚度、芯包折射率差、芯包比等参量与光纤弯曲性能的关系,并据此制作了几种超细低水峰抗弯损光纤.该光纤的裸光纤直径约80 μm,涂覆后成品光纤直径约140 μm,当弯曲半径不小于7.5 mm时,能够在1 260～1 625 nm整个波段内满足DWMD的传输要求.     

基于薄芯光纤模态干涉技术的曲率光纤传感器

提出了一种新的基于薄芯光纤模态干涉技术的光纤曲率传感器。在单模光纤的中间部分插入薄芯光纤用于传感光路,没有插入薄芯光纤的单模光纤用于参考光路,以消除环境对曲率测量的影响。由于插入的薄芯光纤和单模光纤纤芯失配,导致包层的高次模被激发,并与纤芯模在单模光纤内形成干涉。当改变薄芯光纤的曲率时,沿纤芯和包层传播的模态和光纤长度会发生改变,使得干涉谷峰发生平移。将传感光纤的两端固定的平移台上,当调节平移台距离时,薄芯光纤的曲率发生改变,导致干涉谷峰向短波方向平移。通过观察谷峰的平移距离可以实现曲率的传感测量。实验表明,该装置具有低损耗、低成本和高灵敏度的特点。     

基于空芯微结构光纤拉曼探针的实验研究

表面增强拉曼散射(SERS)技术可有效增强样品分子的拉曼信号,对生物分子检测具有较高的灵敏性,因此在生化方面有着许多潜在的应用.而将空芯微结构光纤与SERS技术相结合不仅能够远端实时、分布式地检测,同时还可以增加光场与待测物的有效作用面积,减少传统光纤探针无法避免的石英背景信号等问题.本文基于空芯微结构光纤进行SERS探针的制备及性能测试研究,利用真空物理溅射法在空芯光纤内镀纳米Ag膜,从而制备成SERS探针,通过实验检测不同浓度的罗丹明6G (R6G)酒精溶液的拉曼信号.结果表明,在探针的近端正面成功探测到了浓度低至10~(-9)mol/L的R6G拉曼信号,在探针的远端反面探测到的浓度可小于10~(-6)mol/L.该实验结果为研究高灵敏度的SERS探针提供了一种新的手段.     

基于双向拉曼放大的布里渊光时域分析系统

报道了一种基于双向拉曼放大的布里渊光时域分析系统(Brillouin optical time domain analyzer,BOTDA).利用双向拉曼抽运对信号光进行拉曼放大以补偿光纤损耗及布里渊抽运波的消耗,从而使光纤后端的测量分辨率得到改善,测量分辨率在整段传感光纤趋于一致,同时避免了调制不稳定性引起的频谱扩展,克服了传统BOTDA存在的信号强度指数下降的弊端,使传感精度得到进一步提高.实验实现了50 km传感距离, 温度分辨率达0.6 ℃,空间分辨率为50 m.实验测量并分析了基于双向拉曼放大的BOTDA信噪比和光功率分布特性. 关键词： 分布式光纤传感 受激拉曼放大 布里渊增益 布里渊光时域分析     

Multi-color miniature dual-axis confocal microscope for point-of-care pathology

We present a miniature microelectromechanical systems-based dual-axis confocal microscope capable of spatially coregistered fluorescence and reflectance imaging at multiple wavelengths. This device has a 10 mm diameter scan head with a 2 mm diameter tip for convenient use during surgery to guide tumor resection. The microscope has an adjustable focal depth of 20-200 micrometers and is capable of imaging with an axial resolution of 9 micrometers and in-plane resolution of 4 micrometers over a field of view of 450×450 micrometers. Simultaneous two-color imaging of individual optical sections is achieved by using a pair of grating-prism assemblies to compensate for chromatic dispersion in the 2 mm diameter gradient index relay lens at the distal tip of the device. Experimental measurements of the axial response of the microscope, as well as two-color images of a reflective bar target and fresh mouse brain tissues, demonstrate the performance of our device and its potential for multicolor in vivo optical sectioning microscopy.     

Raman spectroscopy based on a single-crystal sapphire fiber

We demonstrate the advantages of using a single-crystal sapphire fiber to perform Raman spectroscopy over using a standard glass fiber. The narrow Raman peaks and the low background signal of a single-crystal sapphire fiber allow for the detection of weaker Raman signals or Raman signals much closer to the incident laser wavelength than with a standard glass fiber, which has a strong broadband Raman spectrum of its own. The Raman spectra of calcite, single-walled carbon nanotubes, and aqueous sodium carbonate solution were collected using a 50 cm long, 200 μm diameter sapphire fiber, and then they were compared with the results using a 50 cm long, 100 μm diameter glass fiber. The Raman spectrum of each tested material becomes indistinguishable due to the background Raman signal of the glass fiber but can easily be seen using the sapphire fiber, which has only a few narrow Raman peaks of its own.     

一种用于拉曼光谱研究的毛细管/双光纤传感器

:本文提出了一种用于拉曼光谱研究的新型毛细管/双光纤传感器,对传感器构型和特性进行了研究,并将其用于四氯化碳样品的研究。结果表明,毛细管传感器的信噪比和灵敏度较普通方法有较大提高     

Photoluminescence and Possible Amplified Spontaneous Emission from π-Conjugated Dye-Doped Thin Film

We prepared transparent polymer films doped with π-conjugated organic dyes around a multimode silica fiber and observed very narrow fluorescence peaks as compared with the fluorescence in solution. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode. The peaks can be explained by amplified spontaneous emissions (ASEs) because the intensity depended linearly on the excitation intensity with a threshold. When the excitation laser was directly coupled to the fiber core, we observed ASE peaks of the optical fiber itself. These fiber ASE peaks shifted to longer wavelength when we varied the excitation to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin.     

基于拉曼组合放大的长距离光纤传输系统

本文改进了一种实现长距离自适应补偿光纤传输的方法.在利用光纤光栅形成的谐振腔产生激光对信号光进行拉曼放大的基础上,再利用双抽运光对信号光进行拉曼放大,从而获得更高的拉曼增益以实现更长距离的自适应补偿光纤传输.使实验自适应补偿传输距离达125km(为目前国际上已报道的最长自适应补偿光纤传输距离).实验测量并理论分析了该长距离光纤传输系统的开关增益、放大的自发辐射噪声、噪声指数和光功率分布的特性,实验结果与理论模型符合很好.     

弯曲光纤针尖及其法向力压电探测技术

本文介绍一种弯曲光纤针尖及其法向力压电探测的新技术.与目前普遍采用的方法不同,弯曲针尖的制作是先利用电阻丝加热,将光纤弯曲成所需的角度,然后再在缓冲氢氟酸中腐蚀成针尖,得到曲率半径为300μm,弯曲角度为120°,长度为500μm的弯曲针尖.同激光或电弧熔拉、弯曲的方法相比,这种方法工艺简单,成本低廉.由弯曲针尖与蜂鸣器压电片组成的悬臂,利用压电片的正、逆压电效应实现弯曲针尖法向力的非光学法探测.实验表明,这种弯尖法向力的探测较直尖切变力具有更高灵敏度,探测距离提高了一倍以上,给实际应用带来很大的便利.     

液芯光纤共振拉曼光谱法检测水中生物分子研究

拉曼光谱是研究水中生物分子重要的有效方法之一,然而由于拉曼散射截面小,特别是水分子的电子激发态能级高,因此水中生物分子的拉曼光谱测量甚为困难。将液芯光纤技术和共振拉曼技术结合起来,可大幅度提高拉曼光谱强度。实验中用可以获得最大的共振拉曼光谱强度的514.5 nm Ar+离子激光激发,分别用石英和Teflon液芯光纤对水中β-胡萝卜素生物分子进行了痕量检测研究。结果表明应用石英液芯光纤和Teflon液芯光纤可分别检测浓度为10-7～10-9mol·L-1和10-9～10-10mol·L-1的β-胡萝卜素。     

Micro-ring cavity mode of dye-doped thin film: Dependence on the excitation energy

We have prepared π-conjugated organic dye specimens embedded in a transparent polymer film and observed a characteristic photoluminescence peak, having very narrow peak width as compared with the fluorescence in solution, when we prepared the film around the perimeter of a multimode silica fiber. The peak position showed no dependence on the excitation wavelength, indicating that it could not be explained by a whispering gallery mode. The peaks can be explained by amplified spontaneous emissions (ASE) because the intensity depended linearly on the excitation intensity with some threshold. When the excitation laser was directly coupled to the fiber core, we observed ASE peaks of the optical fiber itself. These fiber ASE peaks shifted to longer wavelength when we varied the excitation to shorter wavelength, which clearly ruled out the possibility of silicate Raman scattering as the origin.     

Application of a WGM optical fiber probe fabricated by 3D printing technology for glucose concentration measurement

This study proposes a method for manufacturing a whispering gallery mode (WGM) optical fiber probe used for measuring glucose. The principle of the WGM optical fiber probe consists of the bending interference that occurs between the core mode and cladding mode. 3D printing technology was used to create a mold for the optical fiber sensor so that the bent optical fiber sensor was fixed within the mold to ensure a stable bend radius. This method of fabrication allows for easier installation and replacement of the resulting optical fiber compared to WGM optical fiber sensors fabricated by traditional methods. The results of the concentration test showed that as the glucose aqueous solution concentration increased from 0 to 10%, the wavelength was red shifted and the transmission loss gradually increased. At a bend radius of 3.1 mm and an etching diameter of 46 μm, the wavelength sensitivity was 1.475 nm/% and the R-squared value was 0.983, indicating an extremely high sensitivity. These results confirm that the WGM optical fiber probe created in this study can be used to measure glucose concentrations with high sensitivity, and that it is relatively easy to manufacture, install, and replace. Therefore, the proposed WGM optical fiber probe exhibits good performance and is suitable for use as a glucose concentration sensor.     

一种用于滑坡监测的复合光纤装置

针对滑坡体深部位移这一重要指标,基于光时域反射技术,设计了一种蝴蝶结形式的复合光纤装置用于监测深部剪切位移.该传感装置由方形聚氯乙烯树脂管、毛细钢管、光纤、砂浆组合而成.首先在40mm×40mm×500mm(厚2.0mm)的聚氯乙烯树脂方管四周开挖导槽,将Φ1×500mm毛细钢管放置在导槽中.然后用光纤穿入毛细钢管,光纤一端固定,另一端绕制成蝴蝶结形式.最后在聚氯乙烯树脂管外围浇筑Φ110mm的砂浆,制作成圆柱式复合光纤装置.室内边坡模型剪切测试台测试结果表明:该装置对深部剪切位移初测准确度为1mm,最大测量范围为40mm.分析表明该复合光纤装置具有灵敏度高、测量范围大、结构简单易于安装等优点,可以用于滑坡以及野外岩土结构工程等进行现场原位监测.     

Increasing the imaging depth of coherent anti-Stokes Raman scattering microscopy with a miniature microscope objective

A miniature objective lens with a tip diameter of 1.3 mm was used for extending the penetration depth of coherent anti-Stokes Raman scattering (CARS) microscopy. Its axial and lateral focal widths were determined to be 11.4 and 0.86 microm, respectively, by two-photon excitation fluorescence imaging of 200 nm beads at a 735 nm excitation wavelength. By inserting the lens tip into a soft gel sample, CARS images of 2 microm polystyrene beads 5 mm deep from the surface were acquired. The miniature objective was applied to CARS imaging of rat spinal cord white matter with a minimal requirement for surgery.     

LIBS-Raman光谱联合水下探测系统及初步试验

水下激光诱导击穿光谱技术(LIBS)和水下激光拉曼光谱技术(Raman)已在深海成功获得应用,这两种技术探测对象互补、器件类似,两者联合探测可更好的进行深海研究。针对此需求研发了一套LIBS-Raman光谱联合水下原位探测原理样机,整个系统集成于L790 mm×Φ270 mm的舱体内,在舱体前端有光学窗口和水密插头,舱体内部主要包括脉冲激光器、光谱仪、嵌入式计算机和供电转换装置,甲板控制终端通过水密电缆实现对系统的供电、控制和数据采集。该联合系统采用一台双波长脉冲激光器同时作为LIBS和拉曼光谱的激发光源,LIBS采用1 064 nm波长,拉曼光谱采用532 nm波长。双波长激光器发出的光束经分光镜分为两路,经过后向散射光路收集的两路信号分别进入两个小型光纤光谱仪进行分光探测,LIBS采用AvaSpec-ULS2048光谱仪,拉曼光谱采用QE 65000光谱仪。利用搭建的原理样机在青岛近海进行水下原位探测,在实验室开展了水中固体靶的探测,实验结果证明了LIBS-Raman联合光谱探测装置的可行性。下一步将优化系统并开展深海探测应用。     

Theoretical Analyses on the Resolution of Collection Mode Scanning Near-Field Optical Microscopy

Numerical simulations have been carried out in the framework of waveguide theory to model collection mode scanning near-field optical microscopy (SNOM). The theoretical model includes the optical fiber end and describes the metal coated aperture on the probe tip. The developed formalism goes beyond the existing Bethe-Bouwkamp theories for electromagnetic transmission of subwavelength apertures. The finite coating and optical fiber end are now taken into account. The new features enable us to simulate the near-field probes that are widely used in the collection mode SNOM. The emphases of the numerical analyses have been mainly on the resolution mechanism of the microscopy. Influence on the resolution from important parameters of the probe tips, such as the size of the apertures and the probe-sample distance, is extensively studied. The resolution dependence has been analyzed in the light of the near-field coupling efficiency of the probe tip. An optimum tip size has been found which is balanced between the significant signal transmission and the resolution of the device.     

Theoretical evaluation of peripheral nerve stimulation during MRI with an implanted spinal fusion stimulator

This study examines the requirements for nerve excitation near a spinal fusion implant during magnetic resonance imaging. The implant is the Spinal Fusion SpF^® device manufactured by Electro Biology Inc. The electric field induced within the biological medium was calculated using a three-dimensional finite difference model (described in a separate paper by Beuchler et al. from the University of Utah). Magnetic thresholds were obtained for excitation of myelinated nerve fibers that are near the implant. Minimum (rheobase) thresholds were determined for long duration dB/dt pulses, as well as strength-duration time constants (from which thresholds at other durations could be determined) for various geometries between the implant and a myelinated nerve fiber. The lowest thresholds occur when a large (20-μm diameter) fiber is situated near the bare tip of a wire from the implant, and a long duration (2 ms) stimulus is provided for which dB/dt is constant and monophasic. Magnetic thresholds for shorter durations of dB/dt are higher in accordance with a strength-duration law. In a magnetic field having a time derivative of 10 T/s that is uniform over the torso, nerve excitation is possible under worst-case conditions only for nerve fibers that are within 0.14 mm of the bare wire tip of the implant. With 20 T/s, excitation is possible only within 1 mm of the wire tip.