Photoluminescence of green nanophosphors Sr2MgSi2O7 doped with Tb3+ under 374-nm excitation

A series of Sr₂MgSi₂O₇:Tb³⁺ nanophosphors is prepared using a high-temperature solid-state reaction. The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected by Tb³⁺ ions. However, the images of the scanning electron microscope illustrate that the average size of nanoparticles becomes larger with the increase of Tb³⁺ concentration. Unlike earlier investigations on down-conversion emission of Tb³⁺ ion excited by deep ultraviolet light, in this work, the photoluminescence characteristics of Sr₂MgSi₂O₇ nanophosphors doped with different Tb³⁺ concentrations are analyzed under 374-nm excitations. The intense green emission at 545 nm is observed at an optimal doping concentration of 1.6 mol%. The main reason for the concentration quenching is due to the electric dipole-electric dipole interaction among Tb³⁺ ions.     

Er~(3+)∶Yb~(3+)∶Tm~(3+)共掺硼硅酸盐玻璃光致发光温度特性和能级劈裂

高温固相烧结法制备了Er^3＋：Yb^3＋：Tm^3＋共掺硼硅酸盐玻璃．在978nm半导体激光器抽运下,测量了样品在300～573K下光致发光谱强度随温度的变化,讨论了室温时上转换绿光和红光等波段的光谱劈裂．分析了Er^3＋：Yb^3＋和Tm^3＋之间的能量传递机制．研究结果表明,当温度升高时,Er^3＋：Yb^3＋：Tm^3＋共掺硼硅酸盐玻璃的481nm蓝光、517和534nm绿光、以及657nm红光等光致发光强度单调下降,在490K时几乎消失．但900nm左右的近红外光谱则随温度的升高而持续增强,而且其中心波长向短波方向移动．在室温时,光谱劈裂明显,高温时劈裂逐渐消失．     

Eu~(3+)作探针研究铋铕共掺硼硅酸盐玻璃光学特性

利用高温烧结法制备了铕/铋铕共掺硼硅酸盐玻璃系列样品,测量了样品的激发光谱、发射光谱和声子边带谱,利用Eu3+离子作为探针进一步研究了敏化剂Bi3+的掺入对Eu3+发光的影响.结果表明:本文制作的玻璃样品的电子-声子耦合系数比以往报道过的硼铅等玻璃材料的值都要小,但在硼硅酸盐玻璃中掺入Bi3+会使Eu3+的无辐射跃迁概率增加;Bi3+对Eu3+有敏化作用,Bi3+的掺入使材料的共价性增强,对称性降低,这又使得Eu3+的发光整体变强.所以,在硼硅酸盐玻璃体系中,Eu3+发光的增强不仅仅是由于Bi3+对Eu3+的能量传递,而是以上各因素综合作用的结果.     

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Yb3+:Er3+:Tm3+ co-doped borosilicate glasses are prepared.Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared,which are excited by a 978-nm laser diode,are measured,and the mechanisms of energy transfer among Yb3+,Er3+ and Tm3+ ions are discussed.The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power.The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.     

掺Er及Yb-Er共掺Al2O3光波导放大器噪音特性的数值模拟

利用由速率方程、有限元场分布、传输方程构建的综合理论模型,数值求解了掺Er及Yb-Er共掺Al2O3光波导放大器的噪音系数和正反向自发辐射功率.结果表明,随波导长度的增加,当增益开始下降时,噪音系数显著增加.同时显示了抽运功率和掺杂浓度对噪音系数的影响,比较了两种掺杂放大器的噪音系数,Yb-Er共掺比只掺Er的约小0.8 dB.     

脊形掺铒Al2O3光波导放大器级联特性的模拟计算

利用有限元法分析了脊形掺铒Al₂O₃光波导放大器内信号光和抽运光的场模式分布、速率方程求解铒离子五能级系统的粒子数分布.数值模拟了光波导净增益与信号光功率的关系和多个放大器级联的净增益特性.结果表明：级联系统存在着净增益亏损.低掺铒浓度的光波导作前级放大器的组合方式,级联系统总净增益最大.     

Deposition of Er：A12O3 Films and Photoluminescence Characteristics

Er^3 -doped Al2O3 films were deposited on silicon substrates by reactive closed-field unbalanced magnetron sput-tering. The process parameters, such as target bias voltage, substrate bias voltage, O2 gas flows, sputtering gas pressure, were studied. The 1.53μm photoluminescence characteristics from Er^3 were measured. The relations among the PL peak intensity, annealing temperatures, and pump power were experimentally investigated.     

Bi系超导体高T_c相的形成机制

本文研究Bi系超导体高Tc(2223)相的形成机制。提出Bi系氧化物超导体高Tc相的形成过程是:首先Sr-Ca-Cu氧化物(Ca_(0.85)Sr_(0.15)CuO_2)与低Tc(2212)相反应形成高Tc相的核,然后样品内2223相核通过象结晶学中晶体生长那样的方式长大成2223相晶粒。2223相成核过程中Sr-Ca-Cu氧化物的形成途径有两条:一条是通过固相反应从Ca_2CuO_3和SrCaCu_5O_8的平衡中形成;另一条是通过液相反应从2212相,Ca_2PbO_4和CuO之间的反应直接形成。固相反应的速度远小于液相反应的速度,从而2223相核的形成速度在液相反应下得到加快。通过高Tc相的形成机制,提出Pb对Bi系超导体高Tc相形成的作用是:它只加速2223相的成核,而对2223相的成长不起作用。最后利用2223相形成机制,烧制出具有织构的样品。     

Green and red up-conversion emissions and thermometric application of Er^3＋-doped silicate glass

The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.     

银纳米颗粒对CaSrSiO_4:Tb~(3+)光致发光性能的影响

采用高温固相反应法制备了系列的Ag, Tb~(3+)单掺和共掺CaSrSiO_4纳米荧光粉。XRD和SEM分析结果表明, Tb~(3+)和Ag颗粒的掺入对纳米粉末晶体结构的影响较弱,但CaSrSiO_4:0.7Tb~(3+),0.1Ag样品呈现了立方体结构,且颗粒尺寸明显增大。XPS结果显示Ag单质和Ag~+共存于荧光粉中。在243 nm激发下,同时观测到强的545, 415和381 nm的光致发光谱,以及较弱的437, 586和624 nm发光峰。掺入0.1%(摩尔分数)Ag纳米颗粒时,能够使CaSrSiO_4:0.7Tb~(3+)纳米荧光粉的光致发光强度增强25%。最后讨论了掺Ag颗粒浓度对Tb~(3+)的545和381 nm特征峰衰减曲线的影响。