Identification of the relative distribution of rare-earth ions in phosphate glasses

The relative distribution of rare-earth ions R3+ (Dy3+ or Ho3+) in the phosphate glass RAl(0.30)P(3.05)O(9.62) was measured by employing the method of isomorphic substitution in neutron diffraction. It is found that 7.9(7) R-R nearest neighbors reside at 5.62(6) A in a network made from interlinked PO4 tetrahedra. Provided that the role of Al is explicitly considered, a self-consistent account of the local matrix atom correlations can be developed in which there are 1.68(9) bridging and 2.32(9) terminal oxygen atoms per phosphorus.     

The Spectroscopic Properties of Tm and Ho Co-doped YVO4 Crystal

In this paper, the measured results of spectroscopic properties for Tm, Ho co-doped YVO4 crystals are reported. The absorption spectra, fluorescence spectra and calculated spectroscopic parameters are given. The processes of sensitized luminescence of Ho3+ by Tm3+ with 805 nm LD pumping were investigated. It was found that Tm3+ ion in YVO4 has a larger uniform absorption width (～26 nm) and a larger peak and integreted cross-section of absorption at 800nm (～1.4×10-20 cm2 and 246×10-20 cm) than that in YAG and YLF. The high energy transfer efficiency from Tm3+ to Ho3+ (up to 87%) and low pumping threshold (15 mW) show that Tm3+ can efficiently sensitize Ho3+ in YVO4 crystal. The dependence of ～2 μm emission for Ho3+ on the Tm, Ho doping concentrations was preliminarily analyzed and discussed.     

The Spectroscopic Properties of Tm and Ho Co-doped YVO_4 Crystal

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氟锆酸盐玻璃中Tm^3＋和（Tm^3＋＋Ho^3＋）离子的光谱研究

给出氟锆酸（ＺＢＬＡＮ）玻璃中＾Ｔｍ＾３＋和Ｈｏ＾３＋离子的Ｑｔ参量，并与氧化物玻璃中Ｔｍ＾３＋和Ｈｏ＾３＋的Ｑｔ参量进行了比较，用３７５ｎｍ和４６８ｎｍ波长激发单掺ＺＢＬＡＮ中Ｔｍ＾３＋离子，获得来自Ｄ，２，＾３Ｈ４，Ｇ４能级不同发射波长的发光强度随掺杂浓度的变化，而用小于１μｍ的激发波长激发发单掺Ｔｍ＾３＋或Ｈｏ＾３＋样品，获得近红外区发射光谱。文中给出掺杂浓度对于Ｔｍ＾３＋和Ｈｏ＾＋近红外区     

光致变色二芳基乙烯多波长光存储研究

多波长光致变色存储是基于光致变色原理的一种高容量光存储方法.介绍了多波长光存储的存储原理、系统构成和光盘结构.利用三波长光致变色存储实验装置，进行了三波长光致变色存储的实验.结果显示，实验中采用的三种光致变色材料可用于多波长存储，多波长存储读出信号对比度较高，各记录信号之间几乎无串扰.记录信息经50次低速读出后仍保持较高对比度. 关键词： 多波长 光致变色 光存储 串扰     

Photochromism of diarylethene molecules and crystals

Photochromism is defined as a reversible transformation of a chemical species between two isomers upon photoirradiation. Although vast numbers of photochromic molecules have been so far reported, photochromic molecules which exhibit thermally irreversible photochromic reactivity are limited to a few examples. The thermal irreversibility is an indispensable property for the application of photochromic molecules to optical memories and switches. We have developed a new class of photochromic molecules named “diarylethenes”, which show the thermally irreversible photochromic reactivity. The well designed diarylethene derivatives provide outstanding photochromic performance: both isomers are thermally stable for more than 470,000 years, photoinduced coloration/decoloration can be repeated more than 10⁵ cycles, the quantum yield of cyclization reaction is close to 1 (100%), and the response times of both coloration and decoloration are less than 10 ps. This review describes theoretical background of the photochromic reactions, color changes of the derivatives in solution as well as in the single crystalline phase, and application of the crystals to light-driven actuators.     

Lasing characteristics and optimizations of a diode-side-pumped Tm, Ho:GdVO4 laser

A diode-pumped Tm, Ho:GdVO4 laser with a side-pumping configuration is demonstrated for the first time to our knowledge. Optimum Tm and Ho dopant concentrations for GdVO4 are somewhat lower than those for garnet and fluoride crystals. With a 3% Tm, 0.3% Ho:GdVO4 crystal an output energy of 31.2 mJ and a slope efficiency of 14.5% were obtained in normal-mode operation at room temperature.     

Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope

A three-dimensional (3D) rewritable optical memory using photochromic material is described for high-density memory. The bits are recorded in a 3D volume of photochromic material. A transformation of the photochromic molecule between two isomers with different absorption spectra can be stimulated by irradiation with appropriate wavelengths. We show that a nondestructive readout of photochromic memory is possible by use of a small difference in the refractive index of the photochromic isomers in the near-IR range. For this purpose a near-IR laser-scan differential phase-contrast microscope is used. Experimental results of 3D recording and nondestructive reading are presented.     

Photochromic properties of 4-isopropenyl-3-phenylsydnone and its dimer

The paper describes preparation and properties of a photochromic mesoionic compound 4-isopropenyl-3-phenylsydnone and its dimer. A model for the photochromic behaviour is discussed on the basis of measurements of the optical absorption, the kinetics of photochromism, photoconductivity and EPR absorption.     

PHOTOCHROME DYE TRACING IN WATER FLOWS

The properties and uses of photochromic dyes are presented, and the history of the use of various photochromic dyes in fluid flow experiments is discussed. The mechanisms and theory of the changes in properties of various types of photochromic dyes are presented. In response to the need for a water-soluble photochromic dye, a tri-arylmethane dye, Acid Violet 19, was selected for use in two-phase air-water experiments. Its optical and chemical properties are given, and the dependence of its rate constant on various parameters is studied. Details of the use of Acid Violet 19 in fluid flow experiments are presented.     

Yb3+/Ho3+/Tm3+共掺碲酸盐玻璃的上转换白光发射及其机理研究

采用高温熔融法分别制备了Yb3+/Ho3+,Yb3+/Tm3+和Yb3+/Ho3+/Tm3+共掺的碲酸盐玻璃。在980nm红外激光激发下,Yb3+/Ho3+/Tm3+共掺的玻璃样品显示了强的蓝光、绿光和红光发射,分别对应于Tm3+的1 G4→3 H6跃迁、Ho3+的5 F4(5 S2)→5I 8跃迁以及Ho3+的5 F5→5I 8和Tm3+的1 G4→3 F4跃迁。通过对比发现,Yb3+/Ho3+/Tm3+共掺样品中的红、绿光积分发射强度比值(3.95)明显大于Yb3+/Ho3+共掺样品(1.69),这是由于Ho3+和Tm3+间存在交叉弛豫过程3 H4(Tm3+)+5I 6(Ho3+)→3 F4(Tm3+)+5 F5(Ho3+)和3 F4(Tm3+)+5I 8(Ho3+)→3 H6(Tm3+)+5I 7(Ho3+)所致。在激发功率密度为8.2 W.cm-2时,Yb3+/Ho3+/Tm3+共掺样品的上转换发光色坐标值为x=0.345,y=0.338,非常接近于等能白光(x=0.333,y=0.333)。     

氟化物中Yb3+对Ho3+, Tm3+的直接敏化上转换作用

采用双掺杂(Yb^3 ／Ho^3 )和多掺杂(Ho^3 ／Yb^3 ／Tm^3 )方式,研究了氟化物中Yb^3 对Ho^3 ,Tm^3 的直接敏化上转换作用,并对它们在980nm激光激发下的上转换光谱特性进行了比较,对它们的上转换机理作了详细的讨论分析。观测到两处很强的上转换发光,分别是Yb^3 ／Ho^3 共掺杂体系中^5F4^5S2(Ho^3 )→^5Is(Ho^3 )的荧光跃迁和Ho^3 ／Yb^3 ／Tm^3 共掺杂体系中^3H4(Tm^3 )→H6(Tm^3 )的荧光跃迁。还发现由于添加了Tm^3 ,减弱了Yb^3 ／Ho^3 共掺杂体系中Ho^3 在可见光范围的上转换发光强度。     

偏磷酸钛基体中四价铀离子的荧光

本文用蒸发溶液法制备了Th(PO3)4、U(PO3)4及掺杂了U4+的Th(PO3)4:U4+单晶,确定了β-U(PO3)4属于正交晶系Cmca-D2h18点群,α-U(PO3)4和Th(PO3)4都为三斜晶系P1或P1点群,给出了它们的晶格参数.测量了U(PO3)4吸收谱,和Th(PO3)4基体中U4+的激发和荧光谱.在近紫外光激发下,Th(PO3)4:U4+产生一组荧光,对应于U4+离子的6d-5f电子跃迁.270和298nm的荧光寿命约10ns,对应于电偶极跃迁.在波长为553nm绿光激发下,Th(PO3)4:U4+中四价铀的电子产生上转换效应,释放出358和533nm窄带荧光、它们属于U4+的5f-5f电子跃迁,分别对应于3P2-3H4和1I5-3H4。给出了相应的荧光和上转换效应的跃迁能级图.     

微乳液法一步制备NaYF4∶Yb3+，Ho3+@Au

稀土氟化物纳米材料及其贵金属复合物具有独特的光、电、磁性质,在生物标记、光学储存、显示、防伪等领域有着广泛的应用,已成为材料科学领域的研究热点之一。采用微乳液法制备了NaYF₄∶Yb3+, Ho3+和NaYF₄∶Yb3+, Ho3+@Au复合材料,XRD测试表明NaYF₄∶Yb3+, Ho3+的结晶情况良好,无杂质峰,为立方相,NaYF₄∶Yb3+, Ho3+@Au产物的衍射峰中同时含有NaYF₄与Au两种晶相;SEM图像显示两种纳米粒子均为形貌、尺寸较为均一的球形粒晶为58 nm左右;上转换光谱中显示Ho3+在484, 682和767 nm处具有很高的发光强度,分别对应于5S₂→5I₈, 5F₅→5I₈, 5S₂→5I₇跃迁。     

Diffraction efficiency of photochromic absorption gratings

Efficiencies of thick photochromic absorption gratings are theoretically investigated. The treatment is based on a realistic photochromic grating model, which includes both spatial and temporal variations of the absorption coefficient. Simple analytic solutions for dynamic diffraction characteristics are derived. This nonlinear model shows that the maximum diffraction efficiency of photochromic absorption gratings may exceed 10%.     

激光二极管抽运(Tm,Ho)∶YLF激光器光谱特性实验分析

Ho∶YLF晶体的5I7和5I8斯塔克能级分裂数较多,形成2047~2070nm宽的增益谱带,对于可调谐2μm激光及宽带激光放大器研究具有重要意义。理论上分析了(Tm,Ho)∶YLF晶体的能级结构,并对晶体掺杂浓度和长度进行了优化。实验研究了激光二极管抽运微片Tm(原子数分数0.06),Ho(原子数分数0.004)∶YLF激光谱线可调谐特性,调谐范围2.0656~2.0671μm。利用(Tm,Ho)∶YLF晶体的宽增益谱特性,将其作为激光二极管抽运激光放大器,成功地将2.048μm(Tm,Ho)∶GdVO4激光功率放大了2.5倍。实验上测量了(Tm,Ho)∶YLF晶体在强抽运条件下480~492nm及530~550nm可见波段的上转换蓝绿光荧光谱。     

姜黄素苯胺希夫碱稀土配合物的光致变色性能研究

以稀土Ce,La,Nd (Ⅲ) 硝酸盐和配体姜黄素缩二苯胺Schiff碱和姜黄素缩二(4-甲基苯胺)Schiff碱,合成了六种稀土姜黄素配合物。并采用元素分析、红外吸收光谱、摩尔电导、热重-差热等方法对六种配合物进行表征,确定了所合成配合物的化学组成。研究了各种配合物的紫外-可见光谱、荧光光谱的光致变色性能和在有机溶剂中的溶致变色性能。试验表明随着光照时间的延长,配合物的紫外-可见吸收强度和荧光发射峰的强度不断减弱,峰的位置也发生了一定程度蓝移,溶液颜色变浅。停止照射,溶液恢复到光照射前的颜色,光致变色过程可以重复进行,这说明配合物具有良好的光致变色性能,消色反应遵循一级反应动力学规律。配合物在不同的溶剂中紫外-可见吸收光谱的峰强度和位置也有所不同。对配体及配合物与具有光致变色性能的姜黄素与二乙烯三胺形成的一系列配合物的光谱性质进行了比较和讨论。没有发现配体有光致变色的性质,与姜黄素二乙烯三胺所形成的一系列稀土配合物比较,具有光致变色性能配合物引入了苯胺/对甲苯胺配体基团,增大了配体的共轭面,从而引起配合物的紫外-可见吸收强度的增大和荧光发射峰面积的增加。     

Fluorescence studies of the Er ↔ Ho and Er ↔ Tm energy transfer in erbium aluminum garnet

We have studied the flourescence characteristics of Ho³⁺ and Tm³⁺ in ErAlG:Ho, Tm and investigated the Er ? Ho and Er ? Tm energy transfer present in this system. In the infrared, the crystal ErAlG:Ho, Tm presents three groups of sharp lines (centered at ～18 000, ～19 300, and ～21 000 Å), whose intensities are strongly temperature-dependent. The first two groups are attributable to the Tm ³H₄ → ³H₆ transition, while the third group represents the Ho ⁵I₇ → ⁵I₈ transition. In YAlG:Er (50%), Ho(2%), only the Ho emission centered at ～21 000 Å is observed in the infrared. Under pulsed excitation, the emissions at ～17 900, ～19 000, and ～21 000 Å in ErAlG:Ho, Tm present a double exponential decay; the time dependences of the decays of the first two emissions are essentially the same; however, the 19 000 and 21 000 Å emissions present different decay patterns. In YAlG:Er (50%), Ho (2%), on the other hand, the decay of the 21 000 Å emission is purely exponential at all temperatures studied. The above results for ErAlG:Ho, Tm are explained by means of a rate-equation model in which the Ho → Er and Tm → Er transfer are treated as activation-type processes which effect a coupling between (1) the Ho and Tm ions, and (2) the Ho or Tm ions and quenching impurities.     

A comparative study on diode-pumped continuous wave Tm:Ho:YVO<Subscript>4</Subscript> and Tm:Ho:GdVO<Subscript>4</Subscript> lasers

In this paper, we presented experimental results concerning on the laser characteristics of two microchip lasers emitting in the 2 μm range, Tm:Ho:YVO₄ microchip laser and Tm:Ho:GdVO₄ microchip laser. At a heat sink temperature of 283 K, the maximum output power of Tm:Ho:YVO₄ laser and Tm:Ho:GdVO₄ laser is 47 and 34 mW under absorbed pump power of 912 mW, respectively. High efficiency can be achieved for both lasers at room temperature. Nevertheless, compared with Tm:Ho:GdVO₄ laser, Tm:Ho:YVO₄ laser can operate on single frequency with high power easily. At the heat sink temperature of 288 K, as much as 16.5 mW of 2052.3 nm single-longitudinal-mode (SLM) laser was achieved for Tm:Ho:YVO₄ laser. Under the same condition, only 8 mW of 2048.5 nm SLM laser was achieved for Tm:Ho:GdVO₄ laser.