一种高质量最小波长的超低损耗锥形光纤设计（英文）

采用火焰刷法对单模光纤进行加热拉锥,形成具有微纳米量级纤芯半径的光波导结构,并引入不同的绝热系数对低损耗锥形光纤进行优化,使其满足绝热标准.设计出恒定锥角为2 mrad、波长为400μm、纤维半径为4μm具有最佳形状的低损耗锥形光纤.Matlab仿真结果表明,23mm长的低损耗锥形光纤传输透视率为99.7%,63mm长的低损耗锥形光纤抗辐射能力达到99.6%.由于功率被耦合到高阶模式,其损失被充分抑制,具有恒定锥角的锥形光纤可以实现不牺牲传输质量的光耦合传输.     

锥形光纤的偏振特性

随着光通信技术的不断发展，光纤的应用越来越广泛，而锥形光纤以其独特的传光方式越来越多地应用于光纤连接、成像及测量等领域。实验测定了不同锥角和不同长度锥形光纤的偏振特性。理论上，根据麦克斯韦方程组以及边界条件给出了光在理想光纤中的场分布，阐明了实际光纤中光的传输特性。论证了锥形光纤长度与其偏振特性的关系，进而利用几何光学方法对锥形光纤锥角与其偏振特性的关系作了定性说明。并用具体数据进行了定量计算，得出偏振光经锥形光纤传输或耦合后再传输到其终端所得到均是椭圆偏振光的结论。     

直锥形光纤传输性质的研究

光纤通信的发展日新月异,光纤在信息的传输方面起着越来越重要的作用.通过把传输光纤的一端拉制成锥形,研究了光信号在锥形光纤中的传播行为.根据标量波动方程,运用高斯近似法,从理论上说明了光信号在锥形光纤中的传输特性和能量损耗,分析了光功率在光纤中的分布、光纤中基模场的模半径与光纤芯径的关系、光纤中光的传输模式与光纤芯径的关系、锥形光纤的传输效率与锥形光纤尖端直径的关系等.在实验上,用剪断法测量了锥形光纤的传输效率随锥形光纤圆锥角的变化关系.通过选取一系列锥角的大小,测出相应的传输效率,作出?湫是?并用具体数据进行半定量计算,得出锥形光纤顶端锥体的角度及其变化愈大愈光滑,锥形过渡区越短,传输效率就越高的结论.     

锥形透镜光纤聚焦特性研究

锥形透镜光纤(TLF)是实现光纤与平面光波光路(PLC)芯片高效耦合的核心元件。了解和掌握其聚焦特性是指导平面光波光路尾纤封装技术的关键。给出了表征锥形透镜光纤聚焦特性的两个参量出射光斑直径和远场发散角的理论分析模型,其误差小于1.14%;采用光束传播法数值模拟了锥形透镜光纤中的光波传输和模斑的演化,确定了锥形透镜光纤端面出射光斑的大小;优化锥形透镜光纤结构参量为:拉锥长度300μm,锥角0.733°,透镜曲率半径13.485μm;建立了基于数字摄像机的锥形透镜光纤出射光场测试系统,提出了物理光学反向推演法,计算出锥形透镜光纤聚焦光斑尺寸和远场发散角。理论与实验结果有着良好的一致:对于相同结构参量的锥形透镜光纤,实验反推法得到的出射光斑尺寸与理论值相比误差为3.15%,远场发散角误差为3.67%。     

激光熔融拉锥型微型光纤耦合器设计

采用聚焦红外激光光束进行熔融加热,针对激光熔融拉锥型光纤耦合器设计了一种熔融区域长度为200 μm的微型光纤耦合器.使用光束传输法对拉锥长度和耦合区域的宽度进行了模拟并与实验结果比较,在1320 μm的拉锥长度和14 μm的耦合宽度处找到了最优化且低损耗的耦合器尺寸配置.     

激光束的锥台光纤传输

 分析了锥台光纤的传输特性,建立了高斯近似模型,采用模场耦合理论,计算了锥台光纤的功率转换效率。并在激光器的输出光波长为532 nm,多模光纤的数值孔径为0.11,纤芯半径为12.5 μm条件下对细端半径分别为（4±1）,（5±1）,（6±1）,（7±1）和（8±1） μm的锥台光纤的转换效率进行了实验测定。提出利用锥台光纤的圆柱形多模光纤部分传输光功率,锥台部分保证光束质量的传输方案,在保证光束质量的同时能传输较高的光功率。     

一种新型的光纤锥形耦合器

提出了一种光纤波导折射率渐变的新型锥形（Taper）耦合器件，其原理是基于光纤中Ge缺陷在紫外光照射下而产生的光致折射率的变化。利用光纤在高压、低温下渗氢技术使单模光纤的光致折射率变化△n达6×10-3数量级；通过控制曝光条件就可以在光纤中产生一定规律的锥形结构，使单模光纤的模场半径由4．8μm缩小到3．2μm。由耦合波理论分析表明该器件具有较好的基模传输特性。     

全光纤型微环谐振器的研制

环形谐振器因体积小、功能强、结构简洁等优点长期以来一直在光无源、有源器件的设计和制作中发挥着重要的作用。对光纤的弯曲损耗特性进行了深入分析,指出只有采用微细光纤才能降低全光纤法所制作的环形谐振器的尺寸,加宽器件的自由光谱范围(FSR)获得更好的精细度和品质因子。然后,在改进熔融拉锥技术的同时,保持慢变、绝热条件拉制出在80 mm长度范围内具有良好均匀性、半径为5μm的高质量微细光纤,在此基础上采用自缠绕法研制出半径仅为500μm,谐振效果明显加强的全光纤型微环谐振器,从而很好地解决了集成型微环谐振器较高的弯曲损耗和连接损耗问题。     

高性能Ag/AgI红外空芯光纤的研究

采用液相化学镀膜法研制了内面镀有银膜和碘化银膜(Ag/AgI)的高性能空芯红外光纤.分析了绿色导航光和红外激光同时低损耗传输的光纤结构参量.长度1 m、内直径0.7 mm的Ag/AgI空芯光纤不仅在红外有低损耗传输特性,而且首次在波长530 nm处获得了7 dB/m的低传输损耗特性.满足可见光作为导航光的同轴传输要求.通过分析和改进实验工艺参量,有效降低Ag和AgI薄膜的表面粗糙度.给出了高性能Ag/AgI空芯光纤的介质镀膜的具体工艺参量.     

熔锥型微纳光纤耦合器的理论与实验研究

针对熔融拉锥系统制得的熔锥型微纳光纤耦合器,选择适当的连续函数描述其光场分布,采用归一化的三角分布和矩形分布的加权叠加,以及高斯分布和三角分布的加权叠加实现了模场沿耦合器区域的连续变化;利用局部模式耦合理论推导出腰区及腰区附近锥形区的耦合系数计算公式,并得到微纳光纤耦合器输出光功率随拉伸长度的变化曲线.计算结果表明,随着拉伸长度的增加,光能量在两臂中来回交替耦合的程度变小并且呈现包络样,直至腰区耦合功能消失.通过实时监测拉制微纳光纤耦合器的输出光功率,得到火焰扫描宽度以及氢气流量对双纤失去耦合效应拉伸长度的影响:火焰扫描宽度(均匀腰区)越宽,拉伸长度临界值越大;氢气流量(熔融度)越大,拉伸长度临界值越小.实验结果显示,当光纤耦合器腰区直径达到1.6μm时,耦合功能消失,两输出端口光功率相同且恒定,微纳光纤耦合器具备稳定的光学传输特性.     

Experimental measurement and analysis of the optical trapping force acting on a yeast cell with a lensed optical fiber probe

Based on an optical trapping system with a single-lensed fiber probe inserted at an angle, the sub-picoNewton trapping force acting on a yeast cell as a function of the displacement is measured experimentally by the static and dynamic methods, respectively, whose measurement processes are presented in detail. The measured maximum trapping efficiency is 0.07 in our experiment, which is an order of magnitude lower than that of the optical tweezers. The characteristics of the trapping force in the various horizontal directions are discussed. Finally, the analysis of the measurement error shows the factors and their magnitude which cause error, and offers a way to reduce the error in future.     

Demonstration of high extinction ratio modal interference in a two-mode fiber and its applications for all-fiber comb filter and high-temperature sensor

We show that high extinction ratio (>20 dB) modal interference in a two-mode dispersion compensating fiber can be utilized to build a compact, easy-to-fabricate tunable all-fiber optical comb filter. Wavelength tunability over the full free spectral range of the comb filter is demonstrated with an electrical power of 115mW using an on-fiber thin film micro-heater deposited directly on the fiber. In another configuration, the comb filter is used as a temperature sensor with dynamic range of >300 °C and sensitivity of <0.1 °C. The temperature sensor is capable of measuring a temperature as high as 500 °C.     

Method of state code matrixes in the realization of optical switching using Perfect Shuffle

Based on the Left Perfect Shuffle (LPS) optical communication network constructed by cascade multi-stage LPS interconnection, using Looping algorithm, any arbitrary sequence of the input signals can be realized. However, instead of obtaining the simultaneous state codes of the same level node switches through mathematical analytical expressions directly, only routing tags of each channel can be obtained through mathematical analytical expressions so as to draw out topological chart of the network to obtain the state codes implied in the chart. Thus, the states of the switches cannot be directly programmed and controlled by computer in practical application. In this paper, based on the Looping algorithm, a method of stage code matrixes is presented to resolve this problem. By using the method, the simultaneous state codes of the same level’s four node switches can be directly obtained, which is convenient for the computer to provide controlled signals needed to finish the permutation for each node switch. The method of stage code matrixes provides further theoretical basis for the realization of optical switching by integration of Perfect Shuffle and high-speed optical switches.     

Temperature dependence of low loss polymeric AWG

We investigate on the variation of loss and temperature dependence of a polymeric arrayed waveguide grating (AWG) depending on its substrate, by fabricating 16-channel polymeric AWGs with various substrate conditions. Insertion loss for a polymeric AWG on a silicon substrate is measured as low as 3.1 dB. The temperature-dependent wavelength shift for a polymeric AWG detached from the substrate is maintained within 0.1 nm from 20 to 80 °C. But we observe a degradation of insertion loss and a little instability in wavelength characteristics both for the detached polymeric AWG and for a polymeric AWG on a polymer substrate. We investigate on those optical properties of the polymeric AWGs based on measured thermal expansion properties of the polymers.     

Optical arithmetic unit using bit-WDM

A novel arithmetic unit is proposed consisting of a pipelined optical ripple carry adder that adds two words with bits multiplexed by different wavelengths on a single fiber. The addition result is returned to a fiber bus in the same format as the incoming words. The corresponding operand bit pairs are split off the fiber using wavelength division demultiplexers. Full adders compute the sum for each bit pair and the carry from the next lower significant bit pair. The full adder uses couplers and NOT, NOR and novel XOR logic gates constructed using semiconductor optical amplifiers for gain and wavelength shifting.     

Controllable optical bistability and multistability in a rare-earth-ion-doped optical fiber

We investigated the optical bistability and multistability in an Er³⁺-doped ZrF₄–BaF₂–LaF₃–AlF₃–NaF optical fiber inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled via adjusting properly the parameters of the corresponding system. Our scheme may provide some new possibilities for technological applications in optoelectronics and optical-fiber communication.     

A high nonlinearity elliptical fiber for applications in Raman and Brillouin sensors

Raman and Brillouin effects have found special applications in distributed sensing for smart materials and structures. In these sensors, the fiber acts as a distributed sensor, sensing strain and temperature over a range of tens of kilometers and, at the same time, carries this information to the installation that will process them. In order to optimize the fiber to operate under the Brillouin and Raman regimes, a special elliptical fiber with small effective area has been designed, which will allow these sensors to cover longer distances and/or employ lower power lasers.     

Dichroic property of the H2O-groups in α-quartz, LiNbO3 and LiTaO3 in the infrared range

The absorptive peaks of the H₂O-groups were observed in the infrared absorption spectra in the vicinity of 3480 cm⁻¹ in LiNbO₃ and LiTaO₃, and 3580 cm⁻¹ in α-quartz. The absorptions of these lines were found to depend on the vibration direction of the polarized incident light, showing the dichroic property in these crystals. The absorption of the ordinary ray waves is much larger than that for the E-ray waves in the crystals. This observation indicates that the direction of the bond vibrations for the H₂O-groups is perpendicular to the optic axis of crystals. The dichroic property of the H₂O-groups may serve as the tracer to study the local electric field in piezoelectric crystals.     

利用LED的投影系统光源设计

设计了利用多颗LED(Light Emitting Diode,发光二极管)阵列组成的扩展面光源.经过合理的聚光设计使之符合某些投影设备对亮度要求不是很高,但结构紧凑、性能稳定、使用寿命长的要求.结合数学建模和软件模拟的方式设计了一种小巧的反光杯,利用反光杯把LED近180°的发散光束汇聚到60°左右;然后再用一一对应的透镜阵列汇聚为平行光;最后采用柯勒照明方式把较大的面光源阵列汇集到LCD投影屏幕上,从而达到了较高亮度且具有很高均匀性的目的.