玻璃微球表面辉光等离子体聚合物涂层的热稳定性研究

采用辉光放电聚合技术,在不同工作压强条件下在直径为350—400 μm,厚度为2.5—3 μm的玻璃微球上制备了辉光放电聚合物 (GDP)涂层,并对玻璃/GDP微球模拟充气过程进行了热稳定性实验.利用傅里叶变换红外光谱仪、元素分析仪、热重法、体视显微镜和X射线照相技术对GDP涂层的内部结构及其化学键、热稳定性、微球形貌和厚度进行了表征.结果表明:GDP涂层中的碳氢比、不饱和键和C C含量随着制备压强的增大而减小,低压的热稳定性较好,GDP涂层与玻璃微球的结合力提高,流变、起泡和脱层现象也得到明显改善.微球 关键词： 玻璃微球 GDP涂层 热稳定性 结合力     

新一代二维通道电子倍增器的薄膜连续打拿极

概述了传统还原铅硅酸盐玻璃微通道板(RLSG-MCP)及其特点以及MCP的新发展;介绍了材料的二次发射特性,给出了传统MCP薄膜连续打拿极结构特点和形成工艺.在此基础上,重点论述了用半导体工艺技术制作新一代二维电子倍增器——先进技术微通道板(AT-MCP)的薄膜连续打拿极制备新技术,给出了具体工艺和实验结果,示出了电镜照片和实验曲线,指出了新工艺的优点和发展前景.     

减压氩气下基体对激光微等离子体电子温度的影响

以激光微区发射光谱分析仪结合CCD光栅光谱仪为装置，采用二谱线法，以FeⅠ356.54nm和FeⅠ358.12 nm为分析线，在减压氩气下，测量了镁基体、铝基体、硅基体和低碳钢标样6-0中的激光微等离子体的电子温度及其空间分布，给出了相同基体中微等子体电子温度的空间变化趋势和不同基体中相同空间位置处的电子温度的差异并进行了分析.利用测量的结果，以CuⅠ324.75 nm和ZnⅠ334.50 nm为分析线，从电子温度角度探索了两分析谱线相对强度的基体效应，给出了合理的解释. 关键词： 激光微等离子体 电子温度 减压氩气 基体     

半导体玻璃微通道板的研制

介绍了半导体玻璃微通道板的主要性能，并与传统铅硅酸盐玻璃的相关性能进行了比较。阐述了半导体玻璃的研制工艺，研究了利用半导体玻璃材料制备微通道板的工艺途径，开发了靠玻璃本身体电导性质而无需氢还原工艺的微通道板，即半导体玻璃微通道板。研制出孔径为20μm、外径为12mm的半导体玻璃微通道板，实验利用紫外光电法测试了微通道板的增益、闪烁噪声和成像性能。结果表明新型微通道板具有明显的电子增益和低的闪烁噪声，并且通道表面稳定；利用磷硅酸盐玻璃材料可以实现体导电微通道板的制备。     

633nm激发下掺Er3+TiBa玻璃微球上转换发光的形貌共振

制备了掺Er^3 高折射率TiBa玻璃及其玻璃微球，玻璃基材主要成分为：TiO2、BaCO3和SiO2，稀土掺杂量为3wt%的Er2O3.用633nm激光激发测量了它们的上转换绿光发射。证实绿光的发射均起源于Er^3 离子的双光子吸收过程。利用光学微腔理论讨论了玻璃微球荧光光谱中的形貌共振，并用Mie理论公式对共振峰间隔进行了计算，实验结果与计算结果相符。     

用光线量子论研究掺铒磷酸盐玻璃微球发光的形貌共振

介绍微腔研究理论的发展和微球腔中的光线量子论。测试了488nm激光激发下掺铒磷酸盐玻璃微球的1533nm荧光光谱，分析其谱线中的形貌共振现象及形成机制，并将掺铒磷酸盐玻璃微球的荧光光谱和掺铒磷酸盐体玻璃的荧光光谱进行比较。从实验中得到了掺铒磷酸盐玻璃微球产生的单模振荡幅度。     

掺Nd3+玻璃微球发射光谱研究

采用粉末喷烧法制备了掺Nd^3 高折射率TiBa玻璃微球,主要成分为TiO2,BaO和SiO2,微球直径在30μm左右。在带有显微镜的光谱仪上,用514nm激光照射微球的边缘,测量了它们的发射光谱,观察到了微球腔效应导致的光谱结构共振。在较低泵浦阈值(2mW)下,获得了Nd^3 的激射发光。利用光学微腔理论讨论了玻璃微球荧光光谱中的形貌共振,实验结果与计算结果相符。     

掺铒磷酸盐玻璃微球吸收光谱上的形貌共振

利用高温熔融冷却法制备了直径为82．4μm的掺铒磷酸盐玻璃微球，并利用熔融拉丝法制备了锥腰直径为2．3μm的熔锥光纤与其进行耦合，发现了掺铒玻璃微球吸收光谱中出现的等间距分布的滤波谱线。利用光学微球腔理论讨论了玻璃微球吸收光谱中的形貌共振现象，计算出该耦合系统的品质因数为1．31×10^4。利用Mie散射理论计算了谱线的吸收峰位置和峰间间距，计算结果与实验结果相符合。最后比较了两种峰间间距算法的优劣。     

高钾空心玻璃微球的制备

 以无机化合物为初始原料，选择合理的玻璃溶液配方和成球条件，用液滴法制备出直径200 μm，壁厚2 μm，K₂O摩尔分数大于10 %的空心玻璃微球（HGM）。利用扫描电镜X射线能量色谱仪对玻璃球壳的组分进行了分析。结果表明，所制备的高钾空心玻璃微球各项技术指标能基本满足神光-Ⅱ物理实验的要求，微球球壳成份实测结果与理论计算结果吻合。     

低噪声、高增益微通道板的研制

降低微通道板噪声和增加其电子增益是改善微光像增强器信噪比、视场清晰度和亮度增益最好的技术途经之一。采用具有高而且稳定的二次电子发射系数的皮料玻璃和与皮料玻璃的热物理性能相匹配且化学腐蚀速率比皮料大4个数量级的芯料玻璃以及与两者在一切工艺过程相匹配的实体边玻璃，通过优化实体边实芯工艺制作出的高性能微通道板，其暗电流密度小于5×10-13A/cm2，固定图案噪声和闪烁噪声明显降低；在真空系统中，经40μAh电子清刷后，电子增益（800V）大于500。制管实验表明：这种微通道板达到了预期效果。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.