柠檬酸-凝胶法合成ZnGa2O4:Mn2+/Eu3+及其发光性能的研究

采用柠檬酸－凝胶法合成了纯的ZnGa2O4粉末以及ZnGa2O4:Mn^2 /Eu^3 粉末,利用X射线衍射（XRD）、热重及差热分析（TG－DTA）、发光光谱等测试手段对ZnGa2O4和ZnGa2O4:Mn^2 /Eu^3 的结晶过程、发光性质进行了研究。XRD结果表明,柠檬酸－凝胶法合成的样品在500℃。发光光谱测试表明ZnGa2O4:Mn^2 在450nm和506nm处出现两个发射带,前者属于ZnGa2O4基质的发射,后者属于Mn^2 的^4T1→^6A1的跃迁发射。ZnGa2O4:Eu^3 则呈现Eu^3 的特征红光发射,最强峰位于613nm,属于Eu^3 的^5D0→^7F2超灵敏跃迁。通过光谱分析进一步证实了ZnGa2O4:Mn^2 /Eu^3 的发光机理是基质敏化,吸收能量并向激活离子传递能量。     

Sr3B2O6：Tb^3＋，Li^＋绿色荧光粉的发光特性

用高温固相法合成了Sr3B2O6：Tb^3＋,Li^＋绿色荧光粉,并研究粉体的发光性质。发射光谱由位于黄绿区的4个主要荧光发射峰组成,峰值分别位于495,548,598,625nm,对应了Tb^3＋的^5D4→^7F6,^5D4→^7F5,^5D4→^7和^5D4→^7F3特征跃迁发射,548nm的发射最强。激发光谱表现从200—400nm的宽带,可以被近紫外光辐射二极管（near-ultraviolet light-emitting diodes,UVLED）管芯产生的350-410nm辐射有效激发。研究了Tb^3＋掺杂和电荷补偿剂对样品发光亮度的影响。Sr3B2O6：Tb^3＋,Li^＋是一种适用于白光LED的绿色荧光粉。     

ZnGa2O4长余辉发光特性的研究

以ZnO和Ga2O3为原料,采用高温固相法,在不同温度和原料配比下合成了ZnGa2O4。用254 nm的紫外灯照射样品后,发现存在余辉发光,有505和690 nm两个余辉峰,且余辉峰相对强度受原料配比和烧结温度等制备条件的影响。ZnO不足和温度较高时505 nm峰相对强度较高,ZnO过量和温度较低时690nm峰相对强度较高。讨论了余辉峰的来源,认为505 nm峰来源于结构中Ga^3＋替代了部分Zn^2＋后相对变形八面体中Ga^3＋的^2EA→^4A2能级间跃迁;而690 nm峰起源于晶格中出现氧空位V0^＊后变形八面体中氧空位向其周围的O^2-的V0^＊→O^2-跃迁。解释了余辉峰相对强度受制备条件影响的原因：温度较高时ZnO较多挥发导致不足,而ZnO不足会使结构中出现Zn^2＋空位,从而多余的的Ga^3＋出现在这些空位上,其^2EA到^4A2能级间跃迁使505 nm发射占优;而温度较低时ZnO挥发较少,由于ZnO相对Ga2O3氧不足,可形成更多的O空位,有利于690 nm发射占优,这与余辉峰来源的讨论相符合。     

白光LED用新型MgAl2O4/Ce∶YAG透明陶瓷的发光性能

采用金属醇盐法制备MgAl2O4前驱体,通过高温煅烧2～4 h得到纯相MgAl2O4粉体,再将其与YAG∶Ce荧光粉均匀混合,利用热压烧结并结合热等静压处理得到MgAl2O4/Ce∶YAG透明陶瓷。利用X射线衍射、紫外-可见分光光度计等测试手段对样品进行表征。样品由MgAl2O4和YAG两相组成,在340 nm和475 nm有两个激发峰。发射光谱在533 nm有一宽峰,属于Ce3+的5d→4f特征跃迁发射。该透明陶瓷封装蓝光芯片所得白光LED器件在35 mA驱动下的发光效率为133.47 lm.W-1,其寿命及色温稳定性优于采用传统方式封装的白光LED。实验结果表明MgAl2O4/Ce∶YAG透明陶瓷是一种可用于白光LED的新型荧光材料。     

共掺Mo6+离子的Ca4LaNbW4O20∶Eu3+荧光粉的发光特性

采用高温固相法制备了红色荧光粉Ca4LaNb(W1-x Mo x)4O20∶Eu3+并研究了样品的发光性质。Ca4LaNbW4O20∶Eu3+的激发光谱中包含一个宽的激发带,峰值位于275 nm,归属于WO2-4基团的电荷迁移跃迁。随着Mo6+离子的掺入,Ca4LaNbW4O20∶Eu3+位于275 nm处的吸收带变宽,其原因是O2--Eu3+的电荷迁移跃迁增强。在Ca4LaNb(W1-x Mo x)4O20∶Eu3+的发射光谱中,400~500 nm间较宽的发射带属于WO2-4基团的发射带,而位于591 nm和616 nm的尖锐的发射峰分别属于Eu3+的5D0→7F1磁偶极跃迁和5D0→7F2电偶极跃迁发射。随着Mo6+离子浓度的增加,WO2-4基团的发射带强度下降,从而提高了色纯度。     

（Sr,Ba）Al12O19∶RE^3＋（RE=Ce,Tb）的VUV发光及Ce^3＋→Tb^3＋的能量传递

采用高温固相反应合成磁铅矿型(Sr,Ba)Al12O19∶RE3 (RE=Ce,Tb)发光材料,X射线衍射结果证明生成单一磁铅矿型结构。Ce3 产生302nm的发射峰和340nm左右的不太明显的肩,分别对应于5d→2F5/2和5d→2F7/2跃迁;激发光谱显示两个宽带峰,158nm峰对应于基质吸收,260 nm峰是由4f-5d跃迁引起的。Tb3 的发射光谱显示特征的5D3→7Fj(j=2,3,4,5)和5D4→7Fj(j=4,5,6)跃迁;在激发光谱中,160nm左右的峰是由基质吸收和Tb3 -O2-电荷迁移带交迭产生的,193nm峰是Tb3 的4f-5d自旋允许跃迁引起的,233nm弱的峰是自旋禁戒4f-5d跃迁产生的。Ce3 的发射和Tb3 的f-f跃迁吸收(~320 nm)完全交迭,并且Tb3 的发光强度随Ce3 的浓度增加而增强,从激发光谱看出,Tb3 发光部分来自于Ce3 的吸收,具有Ce3 →Tb3 能量传递。     

Al替代对β-Ga2 O3∶Cr3＋结构与发光性能影响

高温固相法制备了（Ga1- x Alx ）2 O3∶Cr3＋（x＝0,0.1,0.2,0.3,0.4,0.5）系列荧光粉。X射线衍射分析表明Al3＋含量增加后,物相依然保持β-Ga2 O3的相。此外随着Al离子含量的逐渐增加,高衍射角峰位向右移动表明Al离子进入了β-Ga2 O3晶格中。激发光谱中258,300,410和550 nm左右的峰位分别对应基质Ga2 O3的带与带的吸收跃迁、电荷迁移带跃迁、Cr3＋的4 A2→4 T1以及4 A2→4 T2跃迁。随着Al离子掺杂量的增加,激发光谱峰位都呈现出不同程度的蓝移现象,这分别是由于基质的带隙能量、C r3＋与配体之间的电负性以及晶场强度增大所导致的。在发射光谱中,随着Al3＋替代Ga3＋,Cr3＋的发光由宽带发射变为窄带发射,这是由于Al3＋的掺入改变了Cr3＋周围的晶场,从而Cr3＋的红光发射由原来的4 T2→4 A2变为2 E→4 A2跃迁发射。Al离子掺杂改善了样品的长余辉发光特性,并且Al离子含量达到0.5时显示出较长时间的肉眼可见的近红外余辉发射。热释发光曲线显示材料中具有合适的陷阱能级,这也是材料产生长余辉发光的原因。     

(Sr,Ba)Al12O19:RE3+(RE=Ce,Tb)的VUV发光及Ce3+→Tb3+的能量传递

采用高温固相反应合成磁铅矿型(Sr,Ba)Al12O19:RE3 (RE=Ce,Tb)发光材料,X射线衍射结果证明生成单一磁铅矿型结构.Ce3 产生302 nm的发射峰和340 am左右的不太明显的肩,分别对应于5d→2F5/2和5d→2F7/2跃迁;激发光谱显示两个宽带峰,158 nm峰对应于基质吸收,260 nm峰是由4f-5d跃迁引起的.Tb3 的发射光谱显示特征的.D3→1Fi(i=2,3,4,5)和5D4→7Fi(i=4,5,6)跃迁;在激发光谱中,160 nm左右的峰是由基质吸收和Tb -O2-电荷迁移带交迭产生的,193 nm峰是Tb3 的4f-5d自旋允许跃迁引起的,233 nm弱的峰是自旋禁戒4f-5d跃迁产生的.Ce3 的发射和Tb3 的f-f跃迁吸收(～320 nm)完全交迭,并且Tb3 的发光强度随Ce3 的浓度增加而增强,从激发光谱看出,Tb3 发光部分来自于Ce3 的0吸收,具有Cd →Tb3 能量传递.     

SrB4O7：Pr^3 中Pr^3 的发光性质

本研究报道Pr^3 在SrB4O7中的发光性质,在SrB4O7中Pr^3 离子的4f5d能态高^1S0能级,因此,在207nm UV光激发下,Pr^3 能够把所吸收的一个高能量的UV光子转换为两个可见光子的发射(光子倍增);在此氧化物基质中的光子倍增主要是由于田离子处于弱的晶体场格位之中;由于与稀土弱联结相关的声于振动频串低(hωmax-1200cm^-1),因此还能观察到从^3P0能级向低能级的跃迁．第一个光子的发射由1^S0→1^G4(313nm),^1S0→^1D2(338nm)和^1S0→^1I6(405nm)的辐射跃迁组成;第二个光子的发射由^3P0和^1D2能级向低能级的辐射跃迁组成[^3P0→(^3HJ,^3FJ)和^1D2→（^3H4,^3H5)].     

Er玻璃近红外区上转换发光的研究

研究了Er,Yb共掺磷酸盐玻璃的上转换发光，对于在800nm附近的近红外发光进行了分析，认为该发光带是由于三种跃迁引起的，除了常见的4F9/2→^4I15/2跃迁以外，还存在着2H11/2→413/2,4S3/2→4I13/2的跃迁，还研究了Er^3 掺杂浓度对这三种跃迁的影响。     

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.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

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.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

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.