Improvement on peak-to-trough ratio of sampled fiber Bragg gratings with multiple phase shifts

Via a cascaded structure, the peak-to-trough ratio is considerably improved for sampled fiber Bragg gratings （SFBGs） based on multiple-phase-shift （MPS） technique. This cascaded filter is composed of two identical SFBGs which are inserted with the increasing or decreasing arrangement of phase shifts. With this inverse arrangement of MPS in grating design, the phase fluctuation of individual SFBG can be compensated, and as a result an excellent phase matching condition is realized. In this way, the peak-to- trough ratio in reflection spectra is improved from 6 to 12 dB when multiplication factor m = 4, and from 5dBto 10dBwhenm=8.     

海参与聚合物研究

很多生物（比如海参）能以非同寻常的方式改变自身的硬度。最近有工程师提出一类能够改变硬度的聚合物纳米复合材料。美国俄亥俄州西储大学（Case Western Reserve University）的魏德尔（Christoph Weder）与同事研究了各种材料,其中一种是在橡胶样的聚合物中添加坚硬的纤维素纳米纤维。     

Centimetre-Long Single Crystalline ZnO Fibres Prepared by Vapour Transportation

Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800℃ and the substrate temperature is kept at 600℃. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy （SEM）, x-ray diffraction （XRD）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration.     

Structural and Photoluminescence Properties of β-Ga2O3 Nanofibres Fabricated by Electrospinning Method

We have prepared the 13-Ga2 O3 nanofibres by electrospinning method followed by calcining in air at 900℃. The morphology and structure of the nanofibres are characterized by field emission scanning electron microscopy （FE-SEM）, x-ray diffraction （XRD） and Raman technique. These nanofibres have diameters ranging from 60 to 130hm and lengths up to several millimetres. Photoluminescence （PL） spectrum under excitation at 325 nm shows that theseβ-Ga2 O3 nanofibres have a blue emission peaking at 466nm, which may be attributed to defects such as the oxygen vacancies, gallium vacancies and gallium-oxygen vacancy pairs.     

A Fully Vectorial Effective Index Method for Accurate Dispersion Calculation of Photonic Crystal Fibres

A fully vectorial effective index method is developed for accurate dispersion calculation of photonic crystal fibres （PCFs）. In order to improve the accuracy of the model, different values for the effective core radius are used when PCFs have different fibre parameters. The accuracy of our approach is demonstrated by comparing our results with other numerical and experimental results reported in literature. It is found that the accuracy of the fully vectorial effective index method is improved and our results agree well with accurate numerical results obtained by other methods as well as the previously reported experimental data.     

Fabrication of Long-Period Fibre Gratings Using 800 nm Femtosecond Laser Pulses

Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62 × 10^3 J/（cm^2μm）, the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13 × 10^13 W/cm2.     

Widely tunable dual-pump parametric amplifiers with photonic crystal fibres

This paper theoretically studies the double-pumped fibre-optical parametric amplifiers （FOPAs） in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.     

α-K_7P_2W_(17)FeO_(61)纳米纤维的制备与表征

运用高压静电纺丝和程序焙烧方法,制备α-K_7P_2W_(17)FeO_(61)纳米纤维丝。通过红外光谱(FTIR),X射线粉末衍射(XRD)进行了表征,结果表明制备的纳米纤维是纯α-K_7P_2W_(17)FeO_(61),扫描电子显微镜照片(SEM)显示焙烧后产物为纳米纤维丝,直径分布图显示其平均直径大约为1 55nm。     

缅怀龚老一代“光纤人”,牢记使命,继续前进!纪念中国光学学会纤维光学与集成光学专业委员会成立36周年

20世纪50年代,光学纤维初问世之时,中国科学院学部委员龚祖同教授就敏锐地感觉到这种能"转弯抺角"传输光能的光纤是材料科技领域的一个重大革新!他决心在中国开展这方面的研究工作。1962年,龚老担任新成立的中国科学院西安光学精密机械研究所(后文简称"西安光机所")所长,立即组建了光学纤维研究室和光学玻璃研究组。     

基于变权重正交变换的腈纶/棉运动纤维面料近红外光谱识别和信息增强机制

为全面阐释近红外光谱技术在纺织服装行业质量控制中的应用难题,本论文以腈纶/棉混纺纤维运动面料为对象,针对纤维面料的重叠信息精准选择和预处理技术直观化筛选应用进行研究。同时,以混纺纤维中的棉含量为指标,对纺织面料近红外定量模型建立中的分子信息识别和应用机制、建模样品及常规光谱处理对构建模型的影响进行了系统解释。最后,通过变权重正交变换算法计算从分子层面解析了纤维面料谱峰信息差异化贡献及纤维面料散射对定量模型构建和预测稳定性的影响。以期为我国纺织行业及纤维制品的精准化控制和质量表征特异化设备开发提供技术指导和参考。