光源偏振度对光纤陀螺零漂影响的研究

以Y波导集成光学调制器保偏型干涉式光纤陀螺作为研究对象,根据各光学元器件的参数建立了各器件的琼斯矩阵以及光路传输模型,在此基础上进行了光路偏振误差的理论分析。通过推导,得到了保偏型干涉式光纤陀螺的偏振误差表达式,并首次分析了光源偏振度对光纤陀螺零漂的影响。借助光源尾纤输出的光谱,对由0%~3%之间呈线性变化的偏振度以及对经实验测试的光源偏振度的实际值引起的偏振模式耦合误差的零漂值进行了仿真计算。结果表明,当光路中其它参数不变时,由光源偏振度变化引起的零漂值为0.001°/h,满足了高精度光纤陀螺的精度要求。     

塑料光纤纤端光场测试结果及分析

对纤端光场进行了理论分析,分别利用塑料光纤和多模光纤作为接收光纤对塑料光纤的出射纤端光场进行了测量,并与理论分析结果进行了比较,给出了合理的调和参数.传输距离较长的塑料光纤由于高阶模的泄漏,纤端光场分布非常接近高斯分布.实验结果表明了理论分析结果和调和参数选择的合理性.     

顽火辉石的高温高压同步辐射研究

 采用同步辐射能量色散X射线衍射技术、激光加热技术和金刚石对顶砧（DAC）高压装置,在温度为2 000 K和压力为23 GPa的范围内,对采自地幔二辉橄榄岩中的顽火斜方辉石,进行了原位的高温高压能量色散X射线衍射（EDXRD）测量。实验结果表明：当压力为15.3 GPa、温度为1 600 K时（相当于地球内部410 km处的地震波不连续界面的温压环境）,顽火斜方辉石转变为橄榄石的β相——瓦兹利石（Wadsleyite）相;继续加温加压至2 000 K、23 GPa时（相当于地球内部670 km处的地震波不连续界面的温压环境）,顽火斜方辉石相变为钛铁矿（Ilmenite）结构和钙钛矿（Perovskite）结构的混和相。实验结果进一步证明,在地幔中存在的两个地震波不连续界面是由橄榄石、顽火斜方辉石等矿物的相变引起的。     

新型三段高性能的长波段掺铒光纤超荧光光源的研究

提出了一种第一段无泵浦、第二段前向泵浦和第三段后向泵浦的三段级联掺铒光纤超荧光光纤光源的新结构.数值分析了泵浦光波长、铒光纤长度以及泵浦比例对新结构性能的影响.结果表明可以找到一组适合制作成本低廉、输出功率高、谱平坦的长波段掺铒光纤超荧光光源.     

自聚焦透镜高效批量加工的双面研磨抛光法研究

依据双面研磨抛光原理,提出了加工自聚焦透镜平面和斜面辅助工装设计.从工艺技术特点和生产实际过程等方面对设计的工装使用情况进行分析验证.多次大批量加工实践证明,该辅助工装的设计完全满足了自聚焦透镜高效批量加工技术要求,简化整个生产线工艺,减少工艺流程时间,降低材辅料的消耗成本,从而验证了双面研磨抛光法是一种实用的加工自聚焦透镜的新方法.     

纳米颗粒悬浮液池内泡状沸腾的实验研究

本文对纳米颗粒悬浮液在平壁面上池内沸腾进行了实验研究。实验用的纳米粒子为26 nm的铁粉和13 nm的三氧化二铝纳米粉末,基液为去离子水。分别配成体积浓度为0．1％, 1％和2％的悬浮液。实验结果表明,纳米悬浮颗粒对液体沸腾换热过程的影响会随着纳米颗粒性质,颗粒浓度及热流密度大小的不同而出现不同的效果;加入纳米颗粒后, 对基液沸腾换热的影响存在着两个相反的作用机制,它们分别为:纳米颗粒增强了液体内部的热量迁移能力(热物性的影响)和改变了加热面的表面结构特性(加热面特性的影响)。     

BEPCⅡ高频发射机和环流器的调整和测试

北京正负电子对撞机升级改造工程(BEPCⅡ)将采用的频率500MHz、输出功率250kW的高频发射机和环流器已安装、调整、测试和验收完毕,这是国内建立的第一套500MHz/250kW发射机系统.本文将详细介绍机器的调测试的原理和各项测量内容及结果, 并比较设计指标和要求,来阐述此发射机的实际技术指标和测试性能.     

Separate Polarization Modes Synchronization and Synchronization Switches between Vertical-Cavity Surface-Emitting Lasers

For vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated feedback, there exist several synchronization types such as synchronizations between total powers and synchronizations between separate polarization modes. Based on the two-mode rate equations, we study and compare numerically the performances of different synchronization types. Our results show that three synchronization types exhibit good performances when their synchronization conditions are satisfied. They are the complete synchronization between total powers, complete synchronization between x-polarized modes, and generalized synchronization between x-polarized and y-polarized modes. The former two types are sensitive to the injection rate and spontaneous emission, while the third type is contrary. Synchronization type with the best performance may switch from one to another, with changing of injection rate and spontaneous emission factor.     

Effects of Nb2O5 on thermal stability and optical properties of Er3+-doped tellurite glasses

Er³⁺-doped tellurite glasses with molar compositions of xNb₂O₅-(14.7-x)Na₂O--10ZnO--5K₂O--10GeO₂-- 60TeO₂--0.3Er₂O₃ (x=0, 3, 5, 7 and 9) have been investigated for developing 1.5~μm fibre and planar amplifiers. The effects of Nb₂O₅ on the thermal stability and optical properties of Er³⁺-doped tellurite glasses have been discussed. It is noted that the incorporation of Nb₂O₅ (x=5) increases the thermal stability of tellurite glasses significantly. Er³⁺-doped niobium tellurite glasses exhibit a large stimulated emission cross-section (7.2\times 10^-21- 10.7×10^-21~cm² and the gain bandwidth, FWHM×\sigma_e^{\rm peak} (274\times 10^-28 - 480×10^-28~cm³), which are significantly higher than that of silicate and phosphate glasses. In addition, the intensity of upconversion luminescence of the Er³⁺-doped niobium tellurite glasses decreases rapidly with increasing Nb₂O₅ content. As a result, Er³⁺-doped niobium tellurite glasses might be a potential candidate for developing laser or optical amplifier devices.     

Artifact-free black-blood cine cardiac imaging in a single breath-hold

Fast imaging using the STimulated Echo Acquisition Mode (STEAM) sequence can produce cine images of the heart with black-blood contrast. Nevertheless, correction of deformation-related artifacts is required in order to maintain myocardial signal throughout the cardiac cycle. Recent work by our group has eliminated this artifact by combining two STEAM sequences acquired with two different demodulation gradients. Unfortunately, these two STEAM sequences were acquired on two separate breath-holds; thus, scan time doubled. In this work, we present a technique to reduce the total scan time by one half, without sacrificing image quality. The technique is based on interleaving two demodulations within one acquisition in order to obtain quality cine images of the heart in a single breath-hold. The technique was tested on animal models and human subjects, and the impact of interleaved acquisition on image quality was studied using quantitative and qualitative measures.