用网格衰减膜相对标定SIOFM─5FW软X光底片

点聚焦激光等离子体发出的Ｘ射线经晶体色散形成均匀的单色Ｘ射线源，在此基础上，用单层网格作为衰减膜，得到未经衰减和经过衰减的Ｘ射线谱，对无保护膜ＳＩＯＦＭ５ＦＷ软Ｘ光底片作了试验性的相对标定，得到了０．９１ｎｍ波长的特性曲线     

三角形弯晶单色器的分光及聚焦特性研究

北京同步辐射装置(BSRF)的4W1C光束线用斜切角为12.16°的三角形Si(111)、Si(220)和Si(422)晶体在衍射角为23.65°时选择0.252nm、0.154nm和0.089nm波长的单色X光.三角形晶体压弯成柱面,可实现单色光水平方向的聚焦,为漫散射实验站提供聚焦的单色X光.解析计算和SHADOW软件包进行追踪的结果与实验测试结果符合得很好.     

荧光XAFS研究Si可稀浓度杂质的区域结构

荧光ＸＡＦＳ研究Ｓｉ晶体中等电子，缺电子和富电子杂质原子的区域环境结构。结果表明杂质原子的电子构型决定了杂质原子对Ｓｉ区域晶格形变的影响。相对于共价键长ＲＳｉ－Ｓｉ（０．２４０ｎｍ）来说，富电子杂质Ａｓ导致Ｓｉ晶格在Ｓｉ（１１１）方向的ＲＡｓ－Ｓｉ键长产生０．００４ｎｍ的反应增长，等电子杂质Ｇｅ的Ｒ－Ｇｒｅ－Ｓｉ和缺电子杂质Ｇａ和ＲＧａ－Ｓｉ键长收缩０．００２ｎｍ。     

用网格衰减膜相对标定SIOFM—5FW软X光底片

点降焦激光等离子体发出的Ｘ射线经晶体色散形成均匀的单色Ｘ射线源，在此基础上，用单层网格作为衰减膜，得到未经衰减和经过衰减的Ｘ射线谱，对无保护膜的ＳＩＯＦ－Ｍ５ＦＷ软Ｘ光底片作了试验性的相对标定，得到了０．９１ｎｍ波长的特性曲线。     

1.55μmSi_(1-x)Ge_x光波导与Si_(1-x)Ge_x/Si多量子阱探测器集成的优化设计

对１．５５μｍ波长的Ｓｉ１－ｘＧｅｘ光波导和Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱（ＭＱＷ）红外探测器的集成器件结构进行了系统的分析和优化设计。优化结果为：１）对Ｓｉ１－ｘＧｅｘ光波导，Ｇｅ含量ｘ＝０．０５，脊宽、高和腐蚀深度分别为８、３和２．６μｍ；２）对Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱红外探测器，Ｇｅ含量ｘ＝０．５，探测器由厚度为５５０ｎｍ、２３个周期的６ｎｍＳｉ０．５Ｇｅ０．５＋１７ｎｍＳｉ组成，长度约２ｍｍ。结果表明，这种结构器件的内量子效率可达８８％。     

五氧硼酸钾结构的~1H NMR研究

给出相对于外磁场不同取向的五氧硼酸钾（ＫＢ５）单晶的１ＨＮＭＲ室温谱．发现当外磁场在晶体的ｂｃ平面里，１ＨＮＭＲ谱最多有６个峰．而在ａｈ或ａｃ平面里，最多仅有５个峰．用计算机拟合ＮＭＲ谱表明：在五氧硼酸钾中，氢原子是以羟基和水分子集团的形式存在．在羟基集团中，Ｏ—Ｈ的距离为０．１００５±０．００１ｎｍ和０．１０５４±０．００１ｎｍ；而在水分子中，Ｏ—Ｈ的距离为０．０９８３±０．００１ｎｍ和０．０９６８±０．００１ｎｍ，并且Ｈ—Ｏ—Ｈ夹角为１０８°±１°．这些显示本文的数据与中子衍射结果相近，而Ｘ射线衍射所得到的质子位置的数据则与我们的结果相距甚远．     

非晶PET纤维的分子链段取向分布的研究

用对称透射法,收集在室温下不同拉伸比的非晶聚酯（ＰＥＴ）纤维之二有Ｘ射线散射（ＷＡＸＳ）强度函数Ｉ（κ,α）,采用自编ＭＰＳ９６型全谱分峰程序,将不同方位角α测得的ＷＡＸＳ强度曲线上的４个非晶重叠峰进行分解,获得分子链间原子 射引起的２个峰为：ＫＡ＝０．１４１ｎｍ＾－１,ＫＢ＝０．１７２ｎｍ＾－１;分子链内原子 射引起的２个峰为;ＫＣ＝０．３１１ｎｍ＾－１,ＫＤ＝０．５５５ｎｍ＾－１,详细分析了     

北京同步辐射装置X射线漫散射实验站及准周期非晶多层膜的X射线非镜面散射研究

讨论了北京同步辐射装置的４Ｗ１Ｃ光束线和Ｘ射线漫散射实验站的技术特点．利用在漫散射实验站上获得的能量分辨率为４．４×１０－４、光斑大小为０．５ｍｍ（水平）×０．３ｍｍ（垂直）的聚焦单色Ｘ射线光束，研究了准周期非晶多层膜的Ｘ射线漫散射──非镜面散射．实验结果表明，准周期多层膜的漫散射强度分布在倒空间中与表面平行的条纹上并形成散射强度的调制．对散射强度调制进行的模拟计算得到相当满意的结果．     

1.55μmSi1—xGex光波导在Si1—xGex／Si多量子阱探测器集成的优…

对１。５５μｍ波长的Ｓｉ１－ｘＧｅｘ光波导和Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱红外探测器的集成器件结构进行了系统的分析和优化设计。优化结果为：１）对Ｓｉ１－ｘＧｅｘ光波导，Ｇｅ含量ｘ＝０．０５，脊宽，高和腐蚀深度分别为８，３和２．６μｍ，２）对ＳＩ１－ｘＧｅｘ／Ｓｉ多量子阱红外探测器，Ｇｅ含量ｘ＝０．５，探测器由厚度为５５０ｎｍ，２３个周期的６ｎｍＳｉ０．５ＧＥ０．５＋１８ｎｍＳｉ组成，长度约２ｍｍ。     

用平场光栅谱仪现场标定5FW X光底片

采用像散模式的平场光栅谱仪作为分光元件，点状镁激光等离子体Ｘ射线源为原始光源，获得均匀线性单色较Ｘ射线再生源，在此基础上，用多阶梯衰减膜为相对曝光强度标尺，现场标定了上海感光胶片厂生产的５ＦＷ无保护膜Ｘ光底片，给出了５．０ｎｍ～８．０ｎｍ间的底片响应特性。     

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.     

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.     

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.     

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.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

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.