Sixteen-element Ge-on-SOI PIN photo-detector arrays for parallel optical interconnects

We describe the structure and testing of one-dimensional array parallel-optics photo-detectors with 16 photodiodes of which each diode operates up to 8 Gb/s. The single element is vertical and top illuminated 30μm-diameter silicon on insulator （Ge-on-SOI） PIN photodetector. High-quality Ge absorption layer is epitaxially grown on SO1 substrate by the ultra-high vacuum chemical vapor deposition （UHV-CVD）. The photodiode exhibits a good responsivity of 0.20 A/W at a wavelength of 1550 nm. The dark current is as low as 0.36/aA at a reverse bias of 1 V, and the corresponding current density is about 51 mA/cm2. The detector with a diameter of 30 t.trn is measured at an incident light of 1.55 μm and 0.5 mW, and the 3-dB bandwidth is 7.39 GHz without bias and 13.9 GHz at a reverse bias of 3 V. The 16 devices show a good consistency.     

Solar-blind ultraviolet band-pass filter based on metal–dielectric multilayer structures

Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.     

Online charge calibration of LHAASO-WCDA——a study with the engineering array

LHAASO-WCDA is a large ground-based water Cherenkov detector array planned to be built at ShangriLa, Yunnan Province, China. As a major component of the LHAASO project, the main purpose of LHAASO-WCDA is to survey the northern sky for very-high-energy（above 100 GeV） gamma ray sources and measure the spectrum. To gain full knowledge of the water Cherenkov technique and to investigate the engineering issues, a 9-cell detector array has been built at the Yang-Ba-Jing site, neighboring the ARGO-YBJ experiment. With the array, charge calibration methods for both low and high ranges of the PMT readout are studied, whose result shows that a precision at several percentages can be reached, which can satisfy the requirement of the detector array. During the long term operation, the charge calibration stability and environmental afection are studied; in this paper, the results are discussed. These calibration methods are proposed to be applied in the future LHAASO-WCDA project.     

A prototype silicon detector system for space cosmic-ray charge measurement

A readout electronics system used for space cosmic-ray charge measurement for multi-channel silicon detectors is introduced in this paper, including performance measurements. A 64-channel charge sensitive ASIC （VA140） from the IDEAS company is used. With its features of low power consumption, low noise, large dynamic range, and high integration, it can be used in future particle detecting experiments based on silicon detectors.     

半干旱地区太阳光度计定标方法的研究

选用兰州大学半干旱气候与环境观测站2006年9月1日至2007年8月31日的光度计观测资料,以及同期的地面常规观测资料、卫星资料和探空资料,结合冗长绝对法对太阳光度计进行Langley定标。结果表明:选用某一天认为符合条件的观测日定标,其结果误差可能会较大;对各波段的多日定标值直接取平均,计算结果与真值的差别仍会较大;采用期望平均法和拟合平均法检验筛选后,日定标值的离散程度会显著减小,标准差减小了70%~90%;拟合平均法剔除偏离较大的散点后定标值的平均值更接近于真值。     

基于傅里叶变换的强度调制型光谱偏振分析仪

为了获得更高精度的目标光谱偏振特性,结合现有的标准探测器技术与偏振探测技术原理,研制了一种光谱偏振分析仪。采用连续等角度间隔旋转检偏器对目标信号进行强度调制,通过傅里叶级数算法能够显著降低检偏器定位误差引起的偏振度测量不确定度。利用优化设计的测量主光路和大动态范围线性优良的标准陷阱探测器,保证了偏振度测量精度。利用可更换窄带滤光片实现了光谱偏振度测量。经实验验证,在0.1~0.99偏振度的范围内,光谱偏振分析仪的测量不确定度为0.15%。     

Optical Performance of N-Face A1GaN Ultraviolet Light Emitting Diodes

The optical property and injection efficiency of N-face A1GaN based ultraviolet light emitting diodes （UV-LEDs） are studied and compared with Ga-face A1GaN based UV-LEDs. A staircase electron injector is introduced in the N-face AIGaN based UV-LED. The electroluminescence spectra, power-current performance curves, energy band diagrams, carrier concentration and radiative recombination rate are numerically calculated. The results indicate that the N-face UV-LED has a better optical performance than the Ga-face UV-LED, and the injection efficiency is enhanced owing to the fact that the staircase electron injector is available for UV-LEDs.     

Silver Nanoparticle Fabrication by Laser Ablation in Polyvinyl Alcohol Solutions

A laser ablation technique is applied for synthesis of silver nanoparticles in different concentrations of polyvinyl alcohol （PVA） aqueous solution. The ablation of high pure silver plate in the solution is carried out by a nanosecond Q-switched Nd：YAG pulsed laser. X-ray diffraction and transmission electron microscopy are implemented to explore the particles sizes. The effects of PYA concentrations on the absorbance of the silver nanoparticles are studied as well, by using a UV-vis spectrophotometer. The preparation process is carried out for deionized water as a reference sample. The comparison of the obtained results with the reference sample shows that the formation efficiency of nanoparticles in PYA is much higher and the sizes of particles are also smaller.     

威尔逊云室的发明及对物理学的贡献

对历史上第一个粒子探测器---威尔逊云室的发明过程作了较为详细的阐述,同时对威尔逊云室的改进、威尔逊云室对粒子物理学的贡献以及威尔逊本人的生平也作了简要的介绍。     

橙汁中多菌灵农药残留吸收光谱特征研究

利用分光光度计,通过对多菌灵及橙汁-多菌灵混合体系的紫外-可见吸收光谱进行研究,得到橙汁中不同农药含量下的吸收光谱特征,分析了吸光度与多菌灵农药含量的关系。研究表明:多菌灵药液在285nm处有较强的特征吸收峰。通过向橙汁中逐量添加0.28mg·mL-1多菌灵标准溶液,与纯多菌灵药液吸收光谱比较,发现峰值位置出现了小幅度蓝移(285~280nm),说明橙汁和多菌灵发生了相互作用,通过对280nm波长处的吸光度与多菌灵药液含量进行最小二乘法线性拟合,建立了橙汁中吸光度与多菌灵农药含量之间的预测模型,发现吸光度与多菌灵药剂含量具有很好的线性关系,其线性函数模型为:I=2.41+9.26x,相关系数为0.996,回收率在81%~102%之间。根据该回归模型,可以得到橙汁中多菌灵农药残留量的准确值,从而验证了利用紫外-可见吸收光谱测定橙汁中多菌灵残留量的方法的可行性。研究表明,利用光谱技术直接对果汁中农药残留检测方法是可行的,能够满足快速分析的需要,本研究为农药残留检测提供了新的途径。