CaSO4掺Eu和Ag,Mn的热释发光谱

用三维发光谱方法,研究了掺Eu和Ag,Mn的CaSO4热释光材料的发光特性。测定了CaSO4：Eu(0．1％,摩尔分数)经1kGy的^60Co的γ射线照射后的热释发光谱,观察到Eu^2 离子的波长为385nm,温度为120,154℃的两个发光峰,Eu^3 离子在波长590,620,700nm处有多个发光峰。测量样品经不同温度热处理后的热释发光谱,发现Eu^2 和Eu^3 离子的发光强度随热处理温度变化规律极不相同,可见,Eu^2 和Eu^3 浓度比可通过热处理来改变,从而得到需要的Eu^2 和Eu^3 相对发光强度。通过CaSO4：Mn(0．5％)和CaSO4：Eu,Mn(0．1％,0．1％)热释发光谱的比较,观察到Mn^2 不仅是发光中心,而且能起能量转移的作用。实验得到的CaSO4：Eu,Mn磷光体有很高的发光效率。实验结果表明Eu^2 取代CaSO4中的Ca^2 ,不需要电荷补偿,有比较稳定和简单的结构,其热释光峰基本符合以一陷阱和一发光中心为前提的一级动力学模型,Ag和Mn的掺入不产生Eu^2 的高温发光峰。当Eu^3 在CaSO4中取代Ca^2 离子时,因其价态不同,则需电荷补偿,可能产生缺陷复合体和局部跃迁发光,它的热释光发光机制不能用一级动力学方程表示,而Ag的掺入起电荷补偿作用,从而改变了Eu^3 发光峰温,而对Eu^2 的发光峰温影响极小。     

纳米发光材料LnVO4:Eu(Ln=La,Gd,Y)的光谱研究

采用络合溶胶 凝胶法制备了系列纳米发光材料LnVO4:Eu(Ln =La ,Gd ,Y) ,并采用X射线衍射(XRD)、红外光谱 (FTIR)、荧光光谱以及紫外 可见光谱 (UV Vis)对三种发光材料的结构以及发光性质进行研究。结果表明 :YVO4与GdVO4具有相同的结构 ,均属于四方晶系 ,二者具有相似的光谱性质 ;而LaVO4属于单斜晶系 ,受对称性的影响其光谱也相应的发生了变化 ,红外光谱和发射光谱的特征峰发生明显的宽化 ,紫外光谱峰的数目增多     

空间遥感光谱辐射计紫外／真空紫外光谱辐照度定标技术

实验证明了发散光照明模式和平行光照明模式标定的光谱辐照度响应度在定标误差范围内一致．在此基础上构建了由150W大功率氘灯、500W氙灯和球面反射镜组成的平行光光谱辐照度定标单元，该单元解决了大多数光谱辐射计由于在紫外波段响应度低、信噪比小导致的定标困难，而且其输出光谱辐照度在一定距离范围内变化很小从而减小了装调误差，提高了定标准确度．分两个波段标定了一台紫外光谱辐射计160nm～400nm波段光谱辐照度响应度，其中160nm～250nm定标误差4．6％，250nm～400nm定标误差2．4％．     

不同惰性气氛及压强下的碳纳米管的拉曼光谱

本文比较了央弧法中在两种不同气氛和不同压强下制备出的碳纳米管的一级和二级拉曼光谱。我们用直流碳弧法分别在He气氛下和Ar气氛下，压强从11kPa到92kPa制备出碳纳米管，对它们的拉曼光谱进行了分析和比较，发现谱线的峰位置和峰宽度取决于所制备的惰性气氛种类和气体压强。在Ar气氛下制备的碳纳米管的拉曼光谱更接近于石墨的拉曼光谱，而He气氛下制备的碳纳米管，其拉曼光谱与石墨比较，差别较大。并且拉曼位移的峰位置和宽度随着压强的变化而改变，在较高压强下产生的碳纳米管的拉曼光谱更类似于石墨的拉曼光谱。     

单壁碳纳米管吸附酞菁类有机物的研究

利用苯氧基酞菁修饰单壁碳纳米管,并利用透射电子显微镜、紫外可见吸收光谱、荧光光谱以及拉曼光谱进行了表征分析.在透射电镜下观察到结合物呈现糖葫芦状,吸附后吸收光谱以及荧光光谱中峰的强度明显下降说明单壁碳纳米管吸附了大量的苯氧基酞菁,通过拉曼光谱发现吸附后单壁碳纳米管的拉曼光谱中主要峰的位置向长波数方向移动,原因是单壁碳纳米管吸附苯氧基酞菁前后状态的改变导致的.     

光谱纯Y2O3,La2O3,Lu2O3中微量杂质的光致发光谱研究

测定了光谱纯稀土化合物Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３中微量杂质在４８８．０ｎｍ和５１４．５ｎｍ激光线激发下的光致发光谱以及在可见光４４５～７４１ｎｍ范围内吸收谱，Ｙ２Ｏ３，Ｌｕ２Ｏ３样品在４４８．０ｎｍ和５１４．５ｎｍ激光激发下都有发光效应，而Ｌａ２Ｏ３样品只在４８８．０ｎｍ激光激发下才发光，分析了结果表明，Ｙ２Ｏ３，Ｌａ２Ｏ３，Ｌｕ２Ｏ３的发光谱分别是由其存在的微量Ｅｒ＾３＋，Ｓｍ＾３＋和Ｅｕ     

SrAl2O4:Eu,Dy发光材料的制备及其特性研究

采用高温固相合成法制得了SrAl2O4:Eu^2 ,Dy^3 发光材料。该磷光体的合成温度在1300－1500℃范围。X－射线衍射分析（XRD）结果表明该磷光体为SrAl2O4晶体结构，属单斜晶系。其晶格常数为：α=8．4424A，b=8.822A,c=5.1607A,β＝93.415。SrAl2O4:Eu^2 ,Dy^3 发光材料的激发光谱和发射光谱均为宽带谱，激发谱峰位在300－450nm范围内，发射波长在520nm附近。这一结果表明该材料的发光是由Eu^2 的5d→4f宽带跃迁产生的。不同的制备条件，如烧成温度、保温时间等对发光材料的显微结构及其发光性能有较大的影响。     

多孔硅的时间延迟光谱

利用时间延迟光谱技术测量了多孔硅的发光光谱. 实验结果表明,多孔硅的发光是复杂的动力学发光弛豫过程,时间延迟光谱测量技术在研究复杂动力学发光过程方面比稳态光谱测量方法更有效.     

乙二醇溶液中圆锥泡声致发光的发光特性

利用一种改进后的U形管圆锥泡声致发光装置，研究了乙二醇溶液中圆锥泡声致发光的发光特性.实验结果表明，利用乙二醇溶液可以得到超强的单个发光脉冲，其脉冲宽度可以达到150 μs，其值远远高于其他方式产生的声致发光的脉冲宽度.测量得到的光谱为一从紫外到可见光波长范围的连续谱，在589 nm附近叠加有钠的3P-3S原子发射谱线.在钠的原子发射谱线两侧测量得到了Na-Ar分子激发态跃迁形成的蓝卫星带，并在声致发光实验中测得了Na-Ar的红卫星带以及钠的3S-4S原子发射谱线. 关键词： 圆锥泡声致发光 光脉冲 光谱 卫星带     

浓硝酸处理前后多壁碳纳米管的荧光特性研究

对浓硝酸处理前后多壁碳纳米管的荧光特性进行了研究,结果发现多壁碳纳米管在浓硝酸处理前后都能产生荧光;与浓硝酸处理前相比,浓硝酸处理后的多壁碳纳米管的荧光有所增强,且荧光谱峰向短波长方向发生蓝移。碳纳米管产生的荧光与碳纳米管在其缺陷处捕获激发光的能量以及最低空轨道和最高占有轨道之间的能隙有关。多壁碳纳米管在浓硝酸处理前后都有缺陷,因而都能在其缺陷处捕获激发光能量而产生荧光;浓硝酸处理引起多壁碳纳米管的缺陷增多、捕获激发光能量增加因而荧光也随之增强。碳纳米管的最低空轨道和最高占有轨道之间的能隙随其长度减小而增大,浓硝酸处理引起多壁碳纳米管被削短导致其最低空轨道和最高占有轨道之间的能隙增大,因而引起多壁碳纳米管的荧光谱峰向短波方向蓝移。     

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.