不同折射率气体包层环境对微光纤传输光强的影响

基于微纳光纤倏逝场传感理论,通过调制微光纤包层空气的折射率,来探究不同气体折射率环境对微光纤输出光强的影响,从而为制作高灵敏度的特殊气体传感器提供实验指导。实验选择了折射率为1.359 0的丙酮液体和1.494 6二甲苯液体,实验测得相同体积的二甲苯和丙酮在挥发完全后对微光纤束缚光的能力改变不一样,二甲苯使纤芯传输的能量明显减弱,倏逝场能量增强。     

全光纤激光器光束质量的优化

基于激光器的结构,实验研究了影响光束质量的因素。搭建了百瓦级全光纤激光器,在最大泵浦功率为436 W的条件下,在1 080 nm处获得的激光输出为300 W,光-光转换效率为69%,光束质量M²为1.13。实验研究了谐振腔出射的激光光束在传能光纤中传输时径向功率分布的变化,结果显示：随着光束在光纤中传输距离的增加,光纤中的包层光功率呈现出先增加后保持不变的趋势,因而在传输距离上选择不同的长度对包层光进行剥除,可以获得不同的光束质量。实验还显示,在相同的泵浦条件下,与包层光剥离器设置在腔外相比,其设置在谐振腔内可获得更高的激光输出功率,但是光束质量较差。最后,采用在腔内腔外各加一个包层光剥离器的方法获得了更好的光束质量,此时M²为1.07。     

阶跃折射率多模光纤包层等离子体共振传感器

光纤表面等离子体共振(SPR)传感器通常以纤芯为共振基底,需要采用腐蚀、侧抛、研磨等复杂的加工工艺将光纤包层去除,存在倏逝波不易泄露,传感探针制作困难的问题。本文提出一种以光纤包层为SPR共振基底的阶跃折射率多模光纤包层SPR传感器。采用单模光纤与阶跃折射率多模光纤偏芯熔接结构,将单模光纤纤芯中的光直接注入多模光纤包层,并在阶跃折射率多模光纤包层外镀50nm金膜。在探针传感段,光场能量全部分布在阶跃折射率多模光纤包层中,发生SPR效应充分。与传统光纤包层SPR传感结构相比,该传感器能够获得更深的共振谷,折射率测量范围为1.333～1.385RIU时,传感器的平均灵敏度可达2 307nm/RIU,本文亦对传感段多模光纤纤芯直径与长度不同参数的影响进行了探究。本文提出的阶跃折射率多模光纤包层SPR传感器制作简单,有效解决了光纤包层与空气界面不易获得倏逝波的问题。     

光纤湿度传感器

G01N 21/25 CN 1036635A 西屋电气公司(美) 1989.3.27 该传感器包括一根表面包敷1～2μm厚的等离子体聚合的六甲基二甲硅醚与氨的薄膜。这样也层式光纤的光传输特性的变化是该包层所暴露环境的湿度条件的函数。因此将该层式光纤放在环境中,通过经该光纤传输的光并检测经该光纤传输的光的变化,这     

基于CO2激光的微纳光纤熔接技术研究

为了解决微纳光纤之间的结构稳定性差的问题,使用CO_2激光作为加热源,加热两根重叠在一起的微纳光纤,并在显微镜下观察其熔接情况,最终将两根微纳光纤熔接成一根,而且熔接点的光纤表面光滑,直径均匀。通过CO_2激光加热的方法,实现了微纳光纤高质量的熔接,增加了微纳光纤之间的机械稳定性,使其更容易制作出纳米光子器件。     

静电诱导自组装碳纳米管薄膜的结构表征与电学性能

为了给高性能微机电系统（MEMS）薄膜器件提供复合功能薄膜材料,本文将功能化碳纳米管与聚电解质溶液交互沉积技术用于静电诱导逐层自组装碳纳米管/聚合物薄膜。对薄膜制备及其性能的可调控性进行了表征和测试。扫描电镜显微（SEM）形貌观察表明,碳纳米管与聚合物分子链结合致密,形成了质地均匀的随机碳纳米管网络结构。拉曼光谱结果表明,碳纳米管在径向呼吸、缺陷振动、拉伸振动等模式下的指纹特征光谱证实了碳纳米管的有效组装和加载。用石英晶体微天平（QCM）对碳纳米管/聚合物薄膜自组装过程进行了在线实时监测,结果揭示了沉积薄膜厚度和薄膜结构的可调控性。当聚电解质层数由0递增到5时,子层膜厚由6.31 nm增加到111.59 nm,碳纳米管加载体积比由72.35 %减小到14.78 %。此外,基于I-V表征研究了碳纳米管填充体积比及其薄膜厚度对碳纳米管/聚合物薄膜电学特性的影响,为实现碳纳米管/聚合物薄膜电学性能的可调节性提供了实验及理论依据。     

挠性光互联弯曲损耗研究

针对挠性光互联中光纤存在弯曲损耗的问题,文中简要介绍了弯曲损耗产生的原理,采用全矢量有限元法对比研究了SMF-28 单模光纤和G657B光纤的弯曲损耗。研究结果表明,弯曲损耗随入射波长的增加而增加,随弯曲半径的增加而减小。2 种光纤的弯曲损耗相差较大,主要原因在于G657B在光纤结构上的差异,其包层上掺杂了下陷层,增大了芯层和包层之间的折射率的差,增强了光纤芯层的束光能力,降低了光纤的弯曲损耗。文中的研究对光纤在挠性光互联中的应用具有一定的指导意义。     

英开发出新型光纤可用于监测石油管道的泄露

英国曼彻斯特大学科学与技术研究院的费兰克·克瓦斯尼科开发出一种新型光纤 ,可用来监测石油或化学品输送管道的泄露 ,只要将这些光纤沿管道安置好 ,一旦发生泄露 ,马上可以定位并发出警报。一般通讯用光纤的内部 ,是由一个玻璃芯和覆在上面的一层透明化合物包层构成的。玻璃芯与包层的折射率不同 ,匹配适当时 ,光纤即可在其中传输而不会外泄。克瓦斯尼科研制的这种光纤 ,使用了一种含有特定化学成分的可渗透硅质包层 ,当泄露出来的被监测物质与包层中化学成分相遇时 ,即可发生化学反应 ,使包层的折射率改变 ,这样 ,光线就会从中逸出。此时…     

交流电热流场对微纳粒子介电泳行为的影响

以叉指电极阵列为例,分别建立对称物理场、非对称物理场和行波物理场的有限元模型,求解三种情况物理场下微通道中的电场、流场、温度场和介电泳力的分布,分析交流电热流场的对流与传质过程对流场中微纳粒子介电泳的影响规律和干预方式。结果表明,对称物理场和非对称物理场内部均产生漩涡式扰动,增强了流场的对流与传质,可将处于介电泳有效作用范围之外的微纳粒子输送至电极附近区域,扩展了介电泳的实际有效作用区域。行波叉指电极阵列构建的流场则无明显漩涡,但行波物理场中介电泳力的衰减较慢,电极厚度60倍高度处衰减为10%,显著提高了对微纳粒子的操控和输送能力。     

微纳耦合光纤模态声发射传感特性优化研究

为了改善微纳耦合光纤传感器声发射模态识别的能力,立足于模态声发射理论,实验研究了微纳耦合光纤有效传感区结构、长度以及对称性对传感器模态识别能力的影响,分析了优化后传感器模态识别能力的定向性。实验结果表明,当有效传感区结构为包括分离区、锥区和腰区的"X"型结构时,传感器不能识别S_0模态,且识别的A_0模态完整性差;当有效传感区结构为包括腰区和全部锥区的"---"型结构时,传感器能够识别出S_0模态,并完整地识别A_0模态;当有效传感区对称时,所测信号模态完整性好;而当有效传感区不对称时,所测信号完整性较差;"X"型结构时,分离区会衰减声波的部分能量,传感器灵敏度随着有效传感区长度的减小而增大;"---"型结构时,由于锥区起到应变放大作用,传感器灵敏度会随着锥区长度的减小而降低;传感器的模态识别能力随着检测角度的减小而减弱,其有效检测角度范围为45°~135°。该研究对本传感器应用于模态声发射具有指导意义。     

Modeling the electron field emission from carbon nanotube films.

A theoretical framework for the electron field emission from carbon nanotubes (CNTs) is discussed. Using the tunneling theory, the influence of the detailed electron energy dispersion is proven to be of little importance for the electron field emission. By means of numerical computations in a simplified model, the influence of the environment on the local field on a CNT is discussed for an aligned CNT film. In a simple triangular model for the potential energy barrier at the tube end, a tunneling probability was obtained. A statistical model was developed for the structural and functional parameters of aligned CNT films. Practical CNT films of excellent alignment, obtained directly on a tungsten wire by plasma-enhanced chemical vapor deposition, were analyzed by this statistical model. Their distribution in the enhancement factors was thus deduced. An indirect method to get the average electrical parameters of the film using only a limited amount of experimental data was thus established.     

碳纳米管薄膜的制备及其超疏水性研究

采用化学气相沉积法在平面硅基体上制备碳纳米管薄膜,并通过扫描电子显微镜、透射电子显微镜和接触角测量仪对样品进行形貌结构和浸润性质的表征。结果表明:碳纳米管的定向性主要由基体上催化剂粒子的分布控制,并遵循顶部生长生长机制;2种碳纳米管薄膜都具有较大的接触角,获得的定向碳纳米管表面具有微纳米复合结构是产生超疏水的主要原因。     

Effect of formation of grooves in sapphire and filling them with indium under the action of laser radiation

A groove coated with a layer of indium that fills the groove during its formation is generated on the lower surface of sapphire in a single process under the action of laser pulses. The process is performed by using a pulsed gas laser with a wavelength of 0.337 µm. The laser beam is focused through sapphire onto a surface coated with indium. The sapphire motion velocity is uniform, and the sapphire displacement during the time between two pulses is 10% of the light spot diameter. The groove is formed by using the scanning mode (multiple passes of laser radiation through the groove). The pulse energy density in a single pass is sufficiently large. The process is carried out in air. It is found that the optimal option is two passes when the specific resistance of indium in the groove is only 3.8 times greater than the resistance of pure (99.999%) indium bars..     

Structure analysis of sputter-coated and ion-beam sputter-coated films: a comparative study

Gold, platinum and tungsten films were deposited by low energy input (7 mA, 450 V), or high deposition rate (80 mA, 1500 V), diode sputter coating and by ion beam sputter coating. Film structures on Formvar coated grids and on the surface of coated erythrocytes, resin embedded, sectioned, and recorded at high magnification in a TEM were compared using computer-assisted measurements and analysis of film thickness and grain size. The average grain size of the thinnest gold and platinum films was relatively independent of the mode or rate of deposition but as the film thickness increased, significant differences in grain size and film structure were observed. Thick platinum or gold films deposited by low energy input sputter coating contained large grain size and electron transparent cracks; however, more even films with narrower cracks but larger grain size were produced at high deposition rates. Ion beam sputter coated gold had relatively large grain size in 10 nm thick films, but beyond this thickness the grains coalesced to form a continuous film. Platinum films deposited by ion beam sputter coating were even and free of electron transparent cracks and had a very small grain size (1–2 nm), which was relatively independent of the film thickness. Tungsten deposition either by low energy input or ion beam sputter coating resulted in fine grained even films which were free of electron transparent cracks. Such films remained granular in substructure and had a grain size of about 1 nm which was relatively independent of film thickness. Tungsten films produced at high deposition rates were of poorer quality. We conclude that thick diode sputter coated platinum and gold films are best deposited at high deposition rates provided the specimens are not heat sensitive, the improvement in film structure being more significant than the slight increase in grain size. Thick diode or ion beam sputter coated gold films should be suitable for low resolution SEM, and thin discontinuous gold films for medium resolution SEM. Diode sputter coated platinum should be suitable for medium resolution SEM and ion beam sputter coated platinum for medium and some high resolution SEM. 1–5 nm thick tungsten films, deposited by low energy input or ion beam sputter coating should be suitable for high resolution SEM, particularly where contrast is of less importance than resolution.     

分散剂对电泳沉积制备碳纳米管薄膜形貌和场发射性能的影响

采用丙酮、异丙醇、丙酮/无水乙醇混合溶液3种不同的分散剂,利用电泳沉积法在硅基底上制备了碳纳米管(CNTs)薄膜;采用超景深光学显微镜和电子显微镜观察了不同薄膜的表面形貌,并在高真空中对碳纳米管薄膜阴极进行了场发射特性测试。结果表明:以异丙醇作分散剂制备的CNTs薄膜表面均匀连续,场发射性能较好,开启电场和阈值电场分别为0.188V.μm-1和2.8V.μm-1。     

碳纳米管场致发射特性的研究

详细论述了碳纳米管的场致发射特性，包括开启电场、阈值电场、发射电流密度、发射电流的稳定性及场发射电子能量分布等；阐述了场发射的机制；分析了发射特性与其几何结构、吸附态及尖端缺陷等因素的关系；并简要介绍了碳纳米管场发射特性在平板显示领域中的实际应用。     

包覆镍CNTs/AM60复合材料铸态显微组织与力学性能

采用机械搅拌铸造法制备了包覆镍碳纳米管(CNTs)/AM60复合材料,研究了包覆镍CNTs加入量对铸态复合材料力学性能的影响规律,并用扫描电子显微镜观察了复合材料的拉伸断口形貌以及显微组织。结果表明:复合材料显微组织为等轴晶,包覆镍的CNTs主要分布在-αMg共晶相内和晶界处,不仅起到细化晶粒的作用,而且还起到搭接晶粒和强化晶界的作用;复合材料的力学性能随CNTs加入量的增多呈现先增大后减小的趋势,当其质量分数为1%时,抗拉强度、显微硬度、伸长率同时达到最大,比AM60镁合金分别提高了46.23%,41.82%,74.52%,弹性模量在其质量分数为1.2%时达到最大。     

A Monte Carlo study of the thickness determination of ultra-thin films

A Monte Carlo method is utilized to simulate the energy spectra for low-energy electron backscattered from different thin films deposited on different bulk substrates. A method of thickness determination for ultra-thin films is presented, which is obtained from the analysis of the basic characteristics of the energy spectra of backscattered electrons. This method is predicted to be particularly suitable for determining the thickness of ultra-thin films, and to be useful for both cases of light film on heavy substrate and heavy film on light substrate. The thickness resolution is estimated to be as high as subnanometer scale, provided the resolution of the electron energy spectrometer used to be high enough.     

基于微纳光纤Sagnac环结构的光学电流传感器的响应特性研究

磁流体具有固体物质磁性及液体流动性的特性,且无本征矫顽力,无剩磁,磁场响应速度快,灵敏度高,将微纳光纤Sagnac环特殊的光传输性能与磁流体独特的磁光特性相结合,提出了一种基于磁流体包覆微纳光纤Sagnac环的全光纤电流传感器.理论推导了传感器的电流传感机理,设计了传感器的封装方法,并对传感器的温度特性和传感特性进行了...     

Nanomaterial-based gas sensors: A review

The detection of gas molecules is critical for environmental monitoring, chemical process control, agriculture, and medical applications. Therefore, gas sensors and electronic noses (e-nose) are widely studied by researchers all over the world. Graphene has been considered to be a promising gas detection material due to its special electronic properties, which are strongly influenced by the adsorption of extrinsic molecules. Doping of metal oxides and nanometal particles has also been extensively studied and their electrical property is highly sensitive to the properties of absorbed gases. Carbon nanotubes (CNTs) are expensive but have advantages of high sensitivity, good reversibility, and nice stability. Several research groups have studied the mixed structure of the above three materials with their derivatives blended, which show improved gas sensing capabilities. This review summarizes the state-of-the-art progresses in the research on gas sensors and e-nose, based on graphene, metal oxide, and CNTs.