A ferroelectric polyvinylidene fluoride-coated porous fiber based surface-plasmon-resonance-like gas sensor in the terahertz region

In this paper, a ferroelectric polyvinylidene fluoride (PVDF)-coated porous polymer fiber based surface plasmon resonance (SPR)-like gas sensor is proposed theoretically in the terahertz (THz) region based on the total internal reflection (TIR). In such a sensor, the phase matching is achieved by changing the fiber parameters and the plasmon-like phenomenon at the interface between the ferroelectric polyvinylidene fluoride (PVDF) layer and the gaseous analyte is discussed. Using a fullvector finite-element method, the core-mode loss of the fiber is calculated to measure the resolution of the sensor. The amplitude resolution is demonstrated to be as low as 1.45 × 10⁻⁴ RIU, and the spectral resolution is 1.30 × 10⁻⁴ RIU in THz region, where RIU means the refractive index unit.     

Mg掺杂ZnO纳米晶的低温共沉淀法制备及光学性质

采用共沉淀(co-precipitation)法制备了Mg掺杂ZnO纳米晶,分别用X射线衍射(XRD)、傅立叶变换红外光谱(FTIR)、紫外可见吸收(UV-Vis)光谱、光致发光(PL)光谱、透射电镜(TEM)、电子顺磁共振(EPR)等分析手段对样品进行了表征。探究了Mg离子在ZnO纳米晶中的存在状态,ZnO纳米晶颗粒尺寸和发射光谱随Mg掺杂浓度的变化,并对其发光机理进行了分析。结果表明:Mg离子在ZnO晶格中以部分晶格位,部分间隙位的方式存在,没有形成MgO表面壳层结构;随Mg掺杂浓度的增大,ZnO纳米晶的颗粒尺寸变小,发射光的光强增大。发射光的最佳激发波长为342nm,中心波长为500nm,荧光量子产率为22.8%。实验分析表明:Mg离子的掺杂在ZnO纳米晶中引入了锌空位(VZn),间隙位的镁离子(IMg),提供了新的复合中心,从而增强了ZnO纳米晶的光致发光。     

一种5~6 GHz宽带全集成CMOS低噪声放大器

采用55 nm标准CMOS工艺,设计并流片实现了一种应用于Wi-Fi 6(5 GHz)频段的宽带全集成CMOS低噪声放大器(LNA)芯片,包括源极退化共源共栅放大器、负载Balun及增益切换单元。在该设计中,所有电感均为片上实现;采用Balun负载,实现信号的单端转差分输出;具备高低增益模式,以满足输入信号动态范围要求。测试结果表明,在高增益模式下该放大器的最大电压增益为20.2 dB,最小噪声系数为2.2 dB;在低增益模式下该放大器的最大电压增益为15 dB,最大输入1 dB压缩点为-3.2 dBm。芯片核心面积为0.28 mm²,静态功耗为10.2 mW。     

混凝土地面承受重型载荷研究

混凝土地面受到局部重型载荷作用，容易发生混凝土层碎裂，需要一种简单科学的分析混凝土层强度的方法 去解决该类工程问题。运用有限元分析软件，模拟混凝土地面结构受力的方法，在软件模拟中通过设置土弹簧与接触分 析，科学地分析混凝土层强度，为工程施工提供指导。通过具体工程案例的计算，展示该类型问题的具体计算方法。     

金属介电常数对雷达目标散射截面的影响

金属目标的雷达散射截面除了与目标的大小、形状、入射角等有关外还与目标的电磁特性有关,电磁特性的核心就是金属的相对介电常数随频率的变化。低频情况下介电常数是复数,电磁波在导体表面产生感应电流会产生散射场,同尺寸非金属目标的雷达散射截面要远小于金属目标雷达散射截面;高频情况下,介电常数变为实数,金属不再是导体而是电介质了,可以像绝缘体一样反射和透射电磁波,同尺寸的非金属目标的激光雷达散射截面的数值可以大于金属目标的激光雷达散射截面。     

基于液体填充微结构光纤的新型光子功能器件

基于液体材料填充的微结构光纤光子器件有效地将功能材料在不同外界物理场作用下的物理效应同光纤自身的微纳结构结合起来,具有可调谐、设计灵活、全光纤结构和易于集成等优点,是未来光纤光子器件发展的重要方向。掌握不同填充材料、填充方法及所制作器件的不同特性、功能和应用对这一领域的研究具有重要的指导意义。综合阐述了近年来基于液体材料填充的微结构光纤光子器件的研究进展,分析和归纳了各种液态功能材料的种类、物理特性及填充方法,系统阐述了基于该种方法实现的光开关及衰减器、滤波器、调制器、色散补偿器等可调谐光纤光子器件及光纤传感器件,最后对该领域未来的发展方向和前景进行了展望,为未来新型光纤光子器件的研制提供必要的依据和参考。     

C2H2 sensing at V1+V3 band with a hollow-core photonic bandgap fiber

In this paper, we demonstrate the acetylehe (C2H2) sensor with high sensitivity using a hollow-core photonic bandgap fiber (HC-PCF). Experiments for measuring C2H2 concentrations in gas mixture are performed. Using a 2 m-long HC-PCF as gas cell, the spectrum of acetylene at n1+n3 band has been measured, and the P11-branch has been selected for the purpose of sensing. A minimum detectivity of 143 parts per million by volume (ppmv) for the system configuration is estimated.     

Thermal distribution analysis of multi-core photonic crystal fiber laser

The thermal properties of photonic crystal fiber(PCF) laser with 18 circularly distributed cores are investigated by using full-vector finite element method(FEM).The results show that the 18-core PCF has a more effective thermal dispersion construction compared with the single core PCF and 19-core PCF.In addition,the temperature distribution of 18-core PCF laser with different thermal loads is simulated.The results show that the core temperature approaches the fiber drawing value of 1800 K approximately when the thermal load is above 80 W/m which corresponds to the pumping power of 600 W approximately,while the coating temperature approaches the damage value of about 550 K when the thermal load is above 15 W/m which corresponds to the pumping power of 110 W approximately.Therefore the fiber cooling is necessary to achieve power scaling.Compared with other different cooling systems,the copper cooling scheme is found to be an effective method to reduce the thermal effects.