新型硅酸盐长余辉发光材料

首次在硅酸盐体系中发现了余辉时间长达10h以上的高亮度长余辉现象,并采用高温固相法合成了一系列硅酸盐长余辉发光材料。研究发现：Eu^2 ,Ln共激活的镁黄长石结构的焦硅酸盐化合物和镁硅钙石结构的硅酸盐化合物的余辉发光性能最好。研究了各发光材料的光谱特征、长余辉性能,测量了各发光材料的激发光谱和发射光谱以及余辉衰减曲线。同时研究了其应用性能,并测量了发光材料的热释光谱,x射线粉末衍射图谱,确定了发光材料的晶格类型。     

Pr3+掺杂红色长余辉发光材料研究进展

Pr3+掺杂长余辉发光材料因其稳定高效的红色持久性发光而备受关注.近年来,Pr3+掺杂红色长余辉发光材料的基础研究和应用探索均取得了长足的进步.本文总结了Pr3+离子发光特性与电荷迁移带位置的关系,概述了最近报道的发光材料体系,讨论了余辉性能的优化途径,介绍了相关材料在信息加密、交流发光二极管(AC-LED)、生物成像...     

Y2O2S∶Eu,Mg, Ti,Gd 红色长余辉发光材料的热稳定性

采用高温固相法制备了Y₂O₂S ∶ Eu,Mg,Ti,Gd红色长余辉材料,研究了热处理工艺对材料稳定性的影响。用X射线衍射表征该材料的相组成,用激发光谱、发射光谱、余辉亮度对材料的发光性能进行表征。结果表明:热处理温度在600 ℃以下时,材料的发光性能不变;当热处理温度达到800 ℃时,发光性能缓慢下降;当热处理温度达到1 000 ℃时,主晶相Y₂O₂S变成Y₂O₂SO₄和Y₂O₃,发光性能急剧下降。与铝酸盐及硫化物发光材料相比,Y₂O₂S ∶ Eu,Mg,Ti,Gd红色长余辉材料具有较好的热稳定性。     

SrO/Al2O3比率对Sr2AlO4:Eu,Dy发光性能的影响

采用高温固相法合成稀土离子掺杂碱土铝酸盐发光粉,通过改变原料配比分别合成出富Sr和富Al的Sr2AlO4：Eu,Dy发光粉样品。XRD分析结果表明,SrO／Al2O3比率的微小变化不会影响样品的晶相组成。样品的发光性能和长余辉特性测试结果表明,富Al的Sr2AlO4：Eu,Dy发光粉具有较高的荧光强度及较长的余辉时间,说明Sr2AlO4晶格中SrO／Al2O3比率对Sr2AlO4：Eu,Dy发光性能和长余辉特性有很大的影响。激发与发射光谱、发射峰余辉衰减以及热释光谱分析表明,SrO／Al2O3比率的微小变化,导致晶格中发光中心Eu^2 浓度和陷阱的深度与密度发生改变。在富Sr体系中,稀土掺杂离子Eu^2 ,Dy^3 较难进入Sr^2 的晶格位置,晶格中发光中心Eu^2 浓度和陷阱密度都较低,使得粉体发光强度较低,余辉时间较短。     

稀土离子激活长余辉发光材料的最新研究进展

长余辉发光材料是一种新型储能材料。评述了基质组成和制备技术对长余辉发光材料发光特性的影响;介绍了黄绿光、蓝光和红光长余辉材料的最新研究进展和获得长余辉发光的关键因素,即结构缺陷形成的陷阱态和稀土掺杂的作用,并对长余辉发光材料今后的研究和应用做出了展望。     

Nb5+、Sm3+共掺杂YTaO4的长余辉发光性质

采用高温固相法合成了Nb~(5+)、Sm~(3+)共掺杂YTaO_4长余辉发光材料,通过X射线粉末衍射(XRD)、稳态荧光光谱、漫反射光谱和热释光曲线等多种表征手段研究了材料的结构、荧光和长余辉发光特性。XRD结果表明,共掺杂Nb~(5+)和Sm~(3+)没有引起YTaO_4晶体结构的改变。光谱分析表明,共掺Nb~(5+)不仅可大幅提高YTaO_4中Sm~(3+)的长余辉发光强度,而且可实现长余辉发光颜色的调控。对Sm~(3+)和Nb~(5+)共掺杂调控长余辉发光特性的机理也进行了分析。     

Sm~(3+)掺杂对SrLaGa_3O_7自身长余辉发光性质的影响

采用高温固相法制备了Sr La Ga_3O_7∶x Sm~(3+)长余辉材料,通过XRD、荧光光谱、热释光谱分别对样品的结构以及发光性能进行了研究,探究了Sm~(3+)掺杂浓度对样品自身长余辉发光性能的影响。研究结果表明:样品在254 nm紫外光照射后,Sr La Ga_3O_7∶x Sm~(3+)在386 nm有明显的长余辉发光,可持续60 min,主要是由于样品中空位引起的发光。随着掺杂Sm~(3+)浓度的增加,样品的发射光谱和余辉强度先增强后减弱,并出现明显的红移现象,这与Sm~(3+)掺杂所造成的空位浓度密切相关。当Sm~(3+)的摩尔分数达到0.5%时,样品在420 nm处展现最佳的长余辉性质。热释光谱表明掺杂后的样品中存在两种不同的陷阱,分别是由氧空位和锶空位引起的,这两种陷阱不仅影响样品的发光强度,而且充当俘获中心从而影响样品的余辉性能。     

发光搪瓷釉料研究

铕激活的铝酸锶系列超长余辉发粉具有起始亮度高、余辉时间长、无放射性毒害等突出优点,成为当前一类极具发展前途的发光材料,本项目采用该系列发光材料,研究了蓄能发光搪瓷釉料,并制备了性能稳定的发光搪瓷制品。     

红色长余辉材料Y_2O_2S:Eu,Si,M(M=Mg,Ca,Sr,Ba)的制备及发光性能

采用高温固相法合成了红色长余辉材料Y2O2S:Eu,Si,M(M=Mg,Ca,Sr,Ba),利用X晶体衍射、发光光谱、热释光测量等对材料的性能进行了表征。结果分析表明:Y2O2S:Eu,Si,M(M=Mg,Ca,Sr,Ba)长余辉材料的最大荧光发射和余辉发射峰完全一致都位于627nm,产生红光发射,是典型的Eu3+离子的5D0-7F2跃迁。激发停止后,能够产生较好的余辉性能。碱土金属离子能够增强其荧光发射峰强度并对余辉性能有一定促进作用,其中以Mg2+最好,其次是Ba2+。     

新型电子俘获型材料β-Sr2SiO4:Eu2+, La3+长余辉和光激励发光性能的研究

通过高温固相法在还原气体保护下制备出β-Sr₂SiO₄: Eu²⁺, La³⁺系列样品. 通过样品光谱显示, 光致发光、余辉及光激励发光中心均来自于Eu²⁺离子; 并且La³⁺ 的掺入有效增强光致发光、余辉及光激励发光强度. 热释光与余辉衰减测试证明, 与单掺Eu²⁺样品所具备的缺陷数量相比, 共掺La³⁺样品在浅陷阱区(T1区)较多的俘获中心数量是导致其余辉性能优化的主要因素; 其光激励发光强度的增强则归因于在深陷阱(T3区)的俘获中心数量增加. 共掺样品放置15h并在980nm红外激光激励后, 表现出光激励长余辉发光现象. 此现象的出现, 为电子俘获型材料的浅陷阱对深陷阱中的载流子再俘获过程的存在提供了直接证据. 因此, β-Sr₂ SiO₄: Eu²⁺, La³⁺ 材料可视为一种潜在的长余辉和光激励发光材料.     

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.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.