光纤激光器的发展与应用

本文对光纤激光器的现状、发展和应用进行了综述。光纤激光器从掺杂稀土元素发展到掺杂过渡族金属元素;掺杂方法从单纯化学气相沉积（Chemical VaporDeposition,CVD）发展到气相、液相、溶胶-凝胶（sol-gel）和改进的化学沉积（MCVD）等;光纤结构从单包层、双包层到今天的多芯双包层光子晶体光纤;激光功率已经到几十千瓦,光子晶体光纤激光器的功率也已超过1.5 kW。目前,它们广泛应用于造船、航天、机械、电器、汽车、化工等多个领域。新光纤技术的成功,必将推动多种产业的快速发展。     

Study on pure silica core optical fibers

An optimal refractive index profile of pure silica core optical fiber (PSCF) was designed, in combination with the characters of the modified chemical vapor deposition (MCVD) process. Techniques of preform fabrication by a new furnace round heating MCVD process and fiber drawing process were reviewed. Difficulties in doping fluorine in silica, widening the depressed-index cladding and maintaining the index of fiber core were discussed. Methods used to overcome these difficulties were given at the same time. Additionally, the optimal refractive index profiles of PSCF were presented. Supported by the Hi-Tech Research and Development Program of China (Grant No. 2002AA312190), National Natural Science Foundation of China (Grant No. 60477017), Program for the New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023) and the Beijing Jiaotong University Foundation (Grant No. 2006XM003)     

纤维-基体早龄期界面性能的影响因素

通过自行改造的测试系统,实现了对早龄期纤维增强水泥基复合材料体系中纤维–基体界面性能的测定,考察了龄期、基体组成、埋入深度、纤维表面特征等因素对界面性能的影响规律.结果表明:随着龄期的增加,界面的黏结强度逐渐增加,相对密实的基体组成有利于提高界面性能;随着埋入深度的增加,纤维–基体的界面黏结强度降低;而三角形截面及化学沉积改性的纤维与基体之间具有更高的界面黏结强度.     

碳纳米纤维／镍管复合材料的制备

采用化学镀法在化学纤维布表面覆盖均匀镍层,通过热处理去除基体后获得中空镍纤维管;将其置于化学气相沉积装置中,通过调整合适的氢气和甲烷流量比及气压条件制备了以中空微米镍纤维管为主体结构、碳纳米纤维（CNF）以及金属管体结构为存储介质的碳纳米纤维／镍管复合纤维材料．运用扫描电子显微镜（SEM）分析中空镍纤维及复合纤维管表面形貌,x射线衍射（XRD）对复合纤维管晶相组成进行表征．结果表明,利用模版法制备出的中空镍纤维管孔径在10μm左右,管壁厚约0．5μm;化学气相沉积制备过程中,当微波功率500W,氢气和甲烷流量比100：6,气压4．0kPa,沉积时间5min时,复合纤维管外壁和端口内壁均匀沉积长径比较大且直径均匀分布的碳纳米纤维,碳纤维直径约50nm;复合纤维成分为碳纳米纤维、镍和三镍化磷合金相,其中碳纳米纤维表现为石墨相．表面覆盖有碳纳米纤维的镍管复合材料,增加了材料自身的吸附存储和导电性能,可应用于多相催化、电容存储和电极材料等领域．     

基板法铜粒子催化定向生长纳米碳纤维阵列

以乙炔(C2H2)为碳源,铜溶胶为催化剂前躯体,采用化学气相沉积法(CVD)在黄铜基板上定向生长纳米碳纤维阵列。通过扫描电子显微镜(SEM)、X光衍射(XRD)和红外光谱(IR)等手段对产物的形貌、成分进行了表征。结果表明:在反应温度为400～500℃时,制备出了纤维直径为150～200 nm,长度为几到几十个微米的纳米碳纤维阵列;随着反应温度升高或者反应时间的延长,纤维长度增加,负载时间的延长有利于阵列形貌的生成。     

Measurement of Optical Fiber Geometry Parameters with Bessel Function Fitting Method

贝塞尔函数拟合法测量光纤几何参数

李一鸣¹, 项华中¹, 涂建坤², 郑刚^1,*,陈明惠¹, 江斌²

(1 上海介入医疗器械工程研究中心, 教育部重点应用光学实验室, 上海理工大学, 上海200093; 2 上海电缆研究所,上海200093)

中文说明：

光纤的几何参数是衡量光纤质量的重要参数。国标GB15972.20-2008中推荐的光纤几何参数测量方法为近场光分布法。为区分纤芯和包层的边界,需要对光纤进行通光照明。纤芯端面是在图像中显示为一个边缘不清晰的亮斑,无法准确判断纤芯和包层的真实边缘。本文提出一种用贝塞尔函数拟合法测量光纤几何参数的方法。从理论上讲,模场电磁矢量的解满足贝塞尔函数,通过贝塞尔函数拟合可以精确地提取纤芯与包层之间的边界。利用椭圆曲线拟合出光纤的边缘,并计算出光纤几何参数。结果表明,在正常和非正常条件下,光纤直径的平均偏差和重复测量误差均有所减小。该方法是获取光纤边缘数据,提高光纤几何参数精度和稳定性的有效方法。

关键词：光纤几何参数;贝塞尔函数;边缘提取

     

微结构光纤偏振拍长的宽带稳定性及传输特性

针对一种包层空气孔呈外圆内方阵列分布的微结构光纤,仅在包层结构中引入一种非对称结构来调节偏振拍长的宽带稳定性.应用虚位移全矢量有限差分光束传播法分析了内层矩形空气孔阵列的长宽变化对双折射和偏振拍长色散特性的影响.研究结果表明：仅利用一种非对称结构也可以有效地抑制微结构光纤双折射的非线性变化,不仅使偏振拍长在较宽的波长范围内具有较好的稳定性,而且优化后的包层结构中仅有一种尺寸的圆形空气孔,空气孔分布阵列为规则的矩形和圆形阵列,降低了工艺制作的难度.     

[B]杂原子沸石几种改性对烷基化反应影响比较

比较了Ｂ、Ｌａ、Ｐ、Ｐ－Ｍｇ元素改性的［Ｂ］杂原子沸石催化剂,硅烷化的［Ｂ］杂原子沸石催化剂,改性前、后高温水汽处理的［Ｂ］杂原子沸石催化剂,以及经几种方法综合制备的［Ｂ］杂原子沸石催化剂对甲苯／乙烯烷基化反应的影响。通过对［Ｂ］杂原子沸石催化剂的改质,使催化剂的活性、对位产物选择性、以及稳定性都达到了满意的效果。其中以Ｂ改性效果最好,在活性２２．９２％时,对－乙基甲苯选择性达９６．８０％,而且稳定性也好。水汽处理是提高催化剂稳定性的好方法。硅烷化处理后,提高了烷基化反应产物的对位选择性。     

激光化学气相沉积非晶硅

本文报道了CO_2激光化学气相沉积非晶硅的实验结果,硅薄膜的沉积速率与硅烷气压、基片温度和激光光强密切有关。 利用不同方法测量了硅薄膜样品的各种特性,证实了薄膜确为非晶硅。 作者也研究了激光化学沉积非晶硅的机理,并给出了理论讨论以解释实验结果。     

氧化铁可见光光电催化材料改性研究进展

光电催化技术为环境治理和化工生产提供了一条节能、环保的路径。高活性光阳极材料是光电催化技术实际应用的瓶颈问题之一,因此为提高光电催化技术实际应用效率,亟待开发高效的光阳极材料。Fe2O3由于具有禁带宽度窄、稳定性高、价廉等优点成为光电催化研究的热点,且其在光电催化领域展现出良好的应用前景。为获得高效的Fe2O3光电催化剂,研究者针对Fe2O3自身能带位置、导电性差、空穴传输距离短等缺点进行了调控。对近年来在提高Fe2O3催化剂的光电催化性能所采用的制备技术（如水热法、喷雾热分解法、化学气相沉积法、原子层沉积法等）、改性方法（如“结”构建、掺杂、形貌调控等）及其改性后的产氢量进行了概述,并对Fe2O3光电催化剂的发展前景进行了展望。     

Relationship between texture and residual macro-strain in CVD diamond films based on phenomenological analysis

The relationship between texture and elastic properties of chemical vapor deposition （CVD） diamond films was analyzed based on the phenomenological theory, which reveals the influence of crystalline orientation and texture on the residual macro-strain and macro-stress. The phenomenological calculations indicated that the difference in Young＇s modulus could be 15% in single diamond crystals and 5% in diamond films with homogeneously distributed strong fiber texture. The experimentally measured residual strains of free-standing CVD diamond films were in good agreement with the correspondingly calculated Young＇s modulus in connection with the multi-fiber textures in the films, though the difference in Young＇s modulus induced by texture was only around 1%. It is believed that texture should be one of the important factors influencing the residual stress and strain of CVD diamond films.     

Design and fabrication of erbium doped photosensitive fibers

A kind of erbium doped photosensitive fiber (EDPF) was proposed and fabricated, whose core was made of double layers named photosensitive layer and erbium doped layer. The double-layer core design can overcome difficulties in fabrication of EDPF with single core design, i.e. the conflict between the high consistency rare earth doping and high consistency germanium doping. A sample was fabricated through the modified chemical vapor deposition method combined with solution doping technique. The peak absorption coefficient was 48.80 dB/m at 1.53 μm, the background loss was lower than 0.1 dB/m, and the reflectivity of the fiber Brag gratings (FBG) written directly on the sample fiber was up to 97.3% by UV-writing technology. Moreover, a C band tunable fiber laser was fabricated using the sample fiber, in which a uniform FBG was written directly on EDPFs as a reflector. A single wavelength lasing with a maximum wavelength tuning range of 1555.2–1558.0 nm was achieved experimentally. Within this tuning range, the full-width at half maximum (FWHM) of the laser output was smaller than 0.015 nm and the side mode suppression ratio (SMSR) was better than 50 dB. Supported by the National High Technology Research and Development Program of China (863 Project) (Grant No. 2007AA01Z258), the National Natural Science Foundation of China (Grant No. 60771008), Program for New Century Excellent Talents in University (Grant No. NCET-06-0076), Beijing Natural Science Foundation (Grant No. 4052023), and the Beijing Jiaotong University Foundation (Grant No. 2006XM003)     

Influence of cross correlation step length on the surface stress of thin laser cladding Fe314 alloy coatings

To measure the surface stress of thin laser cladding coatings with Rayleigh waves based on the cross correlation function, this pa-per introduced the influence of cross correlation step length on the stress measurement. Flat-shaped specimens made of laser cladding Fe314 alloy coatings were performed by static tensile tests, and Rayleigh wave signals were collected during the test process with an ultrasonic pulser and receiver instrument combined with two Rayleigh wave transducers. The difference in time of flight between two signals was de-termined based on the cross correlation function. The microstructure was observed by scanning electronic microscopy. The influence of the stress on the propagation velocity of Rayleigh waves and the relationship between the difference in time of flight and tensile stress under dif-ferent cross correlation step lengths were analyzed. The inhomogeneous deformation of the coatings affects the relationship between the dif-ference in time of flight and tensile stress; the stress measurement of the coatings is nearly constant with the increase of cross correlation step length when it attains one cycle.     

High-quality graphene grown directly on stainless steel meshes through CVD process for enhanced current collectors of supercapacitors

High-quality graphene coating was directly grown on stainless steel meshes via chemical vapor deposition process, during which the morphology of the stainless steel was transformed rugged. When the graphene-coated stainless steel meshes were applied as current collectors of supercapacitors, the changes of the appearance and the graphene coating improved the contact between stainless steel meshes and the active materials, thus benefiting the performance of the supercapacitors. Furthermore, this simple method can be used to prepare the enhanced current collectors for other energy storage devices.     

激光诱导等离子体淀积薄膜过程的研究

用激波理论推出了激光诱导等离子体化学气相淀积过程中两个重要参量薄膜面积、膜淀积速率的表达式.分析了激光强度、气体压强、基片温度对淀积过程的影响,为最佳淀积条件的选取提供了理论依据.     

A review: Structural oxide coatings by laser chemical vapor deposition

Yttria-stabilized zirconia and α-alumina films were prepared by laser chemical vapor deposition at deposition rates of several hundred micrometers per hour. Moreover, the structural oxide coatings by laser chemical vapor deposition are reviewed. The laser can significantly accelerate the chemical reaction and grain growth in CVD, yielding high deposition rates. The films contain large amounts of nanopores that act as thermal insulation and are thus promising as coating materials for gas turbine blades of Ni-based superalloys and WC-Co cutting tools.     

洋葱状富勒烯的硬脂酸修饰

采用化学气相沉积(chemical vapor deposition,CVD)法制备了洋葱状富勒烯(onion-like fullerenes,OLFs),采用硫酸和硝酸对其进行了预处理。运用硬脂酸对OLFs进行表面修饰,并研究了硬脂酸修饰后OLFs作为润滑油添加剂的分散性和稳定性。采用高分辨透射电镜(high-resolution transmission electron microscope,HRTEM)分析了OLFs的晶体结构和形貌特征,傅立叶红外(Fourier transfer infrared,FT-IR)实验证明,酸处理后OLFs表面含有大量羟基和羧基官能团,通过酯化反应OLFs能够被硬脂酸包覆,显著提高了OLFs在润滑油中的分散性和稳定性。     

薄膜LiMn2O4阴极制备研究进展

尖晶石状LiMn2O4是制备高能量密度的锂离子电池的一种很有发展前景的阴极材料。评论了近年来制备薄膜阴极的方法,包括化学酸基溶解法、溶胶-凝胶法、激光焙烧法、增强型等离子体化学气相淀积法、脉冲激光法、电子束喷射沉积法和射频磁控溅射法。着重分析了能够和IC、MEMS工艺良好集成的射频磁控溅射的方法,提出了工艺路线,并规划了下一步工作。     

带隙型光子晶体光纤及其分析方法

光子晶体光纤是近年来出现的一种新型光纤,其特点是包层排列有规则或随机分布的波长量级的空气孔。包层中的微结构使得光子晶体光纤能够呈现出许多传统光纤不具备的特性,其在光通信领域具有极大的应用前景。文章从光子晶体的概念出发,概述了光子晶体的特征,通过引入光子晶体光纤的概念,介绍了光子带隙型与全内反射型光子晶体光纤的基本结构及导光原理。同时文章简要分析了带隙型光子晶体光纤的各种主要理论研究方法,并对其做出了相应的评价。     

表面覆盖氮化硼膜的金刚石膜的场发射特性

利用热丝化学气相沉积（HFCVD）方法在Si衬底上生长了4μm厚的金刚石膜,然后利用射频磁控溅射方法在金刚石膜上沉积了100nm厚的六角氮化硼（h—BN）薄膜．在超高真空系统中测试了覆盖氮化硼（BN）薄膜前后金刚石膜的场发射特性,结果表明覆盖BN薄膜后的金刚石膜的场发射特性明显提高,开启电场由14V／μm升到8V／μm．F—N曲线表明,覆盖BN薄膜后的金刚石膜在强电场区域的场增强因子有所降低,这可能归因于场发射点随着电场的增强而改变．