荧光光纤温度传感器激励光源的选择

本文分析计算了荧光光纤温度传感器的温敏元件——GsAlAs/GaAs双异质结半导体材料的荧光辐射效率与激励光波长的关系。讨论了温度测量范围及温敏元件GaAlAs层铝含量对激励光源的限制,在0～200℃测温范围内,若采用LED作激励光源,其峰值波长应在0.70～0.76μm之间选择。     

Synthesis and liquid crystalline properties of new amide‐modified poly(1,4‐cyclohexanedimethylene terephthalate)

New series of cycloaliphatic poly(ester‐amide)s, poly(1,4‐cyclohexanedimethyleneterephthalate‐co‐1,3‐cyclohexanedimethylene terephthalamide), were synthesized through solution polymerization route. The compositions of ester/amide units in the copolymers were varied from 0 to 100% by varying the amount of 1,4‐cyclohexanedimethanol and 1,3‐cyclohexanebis(methylamine) in the feed. The structures of the polymers were confirmed by NMR and FTIR, and the molecular weights were determined by inherent viscosity. The composition analysis by NMR reveals that the reactivity of the diamine toward the acid chlorides is lowered than that of diol, which results in the formation of more ester content in the poly (ester‐amides). The thermal analysis indicate that the new poly(ester‐amide)s having less than 10 mol % of amide linkages are thermotropic liquid crystalline from 200 to 250 °C and a thread like nematic phases are observed under the polarizing microscope. WXRD studies suggest that the liquid crystalline domains promote the nucleation process in the polyester chains and increases the percent crystallinity of the poly(ester‐amide)s. The glass transition temperature of the copolymers initially increases with increase in amide units because of the presence of nematic phases and subsequently follows the Flory–Fox behavior. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 42–52, 2006     

Differential AC-chip calorimeter for glass transition measurements in ultrathin films

A differential AC-chip calorimeter capable of measuring the step in heat capacity at the glass transition in nanometer-thin films is described. Because of the differential setup, pJ/K sensitivity is achieved. Heat capacity can be measured for sample masses below 1 ng in broad temperature range as needed for the study of the glass transition in nanometer-thin polymeric films. Relative accuracy is sufficient to investigate the changes in heat capacity as the step at the glass transition of polystyrene. The step is about 25% of the total heat capacity of polystyrene. The calorimeter allows for the frequency dependent measurement of complex heat capacity in the frequency range from 1 Hz to 1 kHz. The glass transition in thin polystyrene films (50–4 nm) was determined at well-defined experimental time scales. No thickness dependency of the glass transition temperature was observed within the error limits (±3 K)—neither at constant frequency (40 Hz) nor for the trace in the activation diagram (1 Hz–1 kHz). © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2996–3005, 2006     

Design,synthesis, and characterization of main‐chain,aromatic polyesters based on 3,4‐ethylenedioxythiophene

A series of new thermoplastic polyesters based on 3,4‐ethylenedioxythiophene (EDOT) with flexible aliphatic spacers have been synthesized and characterized for the first time. The thermal properties of these polyesters based on EDOT are comparable to those of conventional polyesters based on the 1,4‐phenyl unit, indicating that EDOT is a viable replacement for the phenyl units. The glass‐transition and melting‐transition temperatures decrease monotonically with an increase in the spacer length. Theoretical calculations have revealed that the core angle for EDOT is comparable to that of unsubstituted thiophene and hence should be compatible with the formation of the mesophase. This has been confirmed experimentally by the synthesis of a main‐chain, thermotropic, liquid‐crystalline polyester based on EDOT that exhibits fluid birefringence. In fact, this is the first report in which a main‐chain, liquid‐crystalline polymer based on 3,4‐disubstituted thiophene has been successfully designed and synthesized. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3479–3486, 2006     

Spatiotemporal and Thermal Analysis of VCSEL for Short-range Gigabit Optical Links

High-speed Optoelectronic Modules using Vertical Cavity Surface Emitting Lasers (VCSEL) coupled to Multi Mode Fibers (MMF) are a performing and low-cost solution for 10 Gigabit Ethernet (10 GbE) in short-distance optical links. A complete model of the spatiotemporal behavior of multimode VCSELs, through static and dynamic response, noise, thermal effects, and its coupling to MMF has been investigated. Relative Intensity Noise shows modal dependence and can be affected by spatial filtering due to coupling and fiber propagation. Simulations permit to evaluate critical parameters, such as modulation formats, launching conditions, and operating temperature for global bandwidth and eye diagram optimization up to 10 Gb/s. Simulation results are compared to measurements on prototype optoelectronic modules.     

Formation and magnetic properties of Co–Fe-based bulk metallic glasses with supercooled liquid region

A new Co–Fe-based ferromagnetic bulk metallic glass (BMG) was synthesized by copper mould casting method. The thermal stability and crystallization processes were investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The soft magnetic behavior was studied by DC magnetic measurements. The high glass formation ability was interpreted in terms of the effective suppression of nucleation and growth of the intermetallic compounds which appear in the multicomponent system during solidification. The high thermal stability indicates that the new Co–Fe-based BMG could be used as high-temperature magnetic material. The low coercivity which was as low as 8 A/m for the as-cast sample was found in the Co–Fe-based metallic glass cylinder with a diameter of 1.5 mm.     

800nm激光泵浦掺Nd^3＋的氟化物玻璃光纤正向双程超荧光分析

从实验上探讨了掺Ｎｄ＾３＋的氟化物玻璃光纤正向双程超荧光基本特性，包括输入－输出特性、输出－带宽特性以及输出－波长（激发）特性。并给出了理论上的拟合公式，实验表明利用氟化物玻璃光纤有望获得性能优异的有应用前景的低相干度集成化光源。     

气密性碳涂覆光纤筛选强度与电阻关系研究

通过实验分析确立了把光纤电阻作为衡量气密性碳涂覆光纤通过２％应变筛选的过渡标准。要拉制２％应变筛选的碳涂覆光纤，其电阻值应小于３０ｋΩ／ｃｍ。     

线圈型全光纤偏振器的研究

本文采用等效电流法对线圈型全光纤偏振器进行了分析计算.对应于保偏光纤中两正交传输基模的消光比,提出了一种分析保偏光纤弯曲损耗的新方法,这种方法基于将保偏光纤两个不同偏振模式分别等效为两个普通圆光纤的基模,等效参数通过测量不同偏振模式的模场半径来确定.实验证明这种理论计算方法与实验结果一致.最终,我们研制出的线圈型光纤偏振器在1.31μm工作波长下,实测消光比达30dB以上,工作偏振模式插入损耗≤3dB.