Investigation on 1.07 μm laser emission in Nd~（3＋）-doped sodium fluoroborate glasses

Spectroscopic and fluorescence properties of Nd 3+ ions in sodium fluoroborate(SFB) glasses were prepared and characterized through optical absorption,emission and decay measurements.The energy level analysis was carried out using free-ion Hamiltonian model.Experimental oscillator strengths were determined by measuring the area encompassed by the absorption peaks recorded for 1.0 mol.% Nd 3+-doped glasses.The Judd-Ofelt parameters(2,4,6) were used to evaluate the laser characteristic parameters such as radiative transition probability(A R),radiative decay time(τ R),fluorescence branching ratio(β R) and stimulated emission cross-section(σ e) for the 4 F 3/2 metastable state.The fluorescence spectra for different concentrations of Nd 3+ ions were recorded by exciting the samples at 514.5 nm Ar + ion laser.     

Fabrication and gain performance of Er^3＋/Yb^3＋-codoped tellurite glass fiber

Er^3＋/Yb^3＋-codoped TeO2-ZnO-BaO-La2O3 tellurite glass fiber was fabricated by rotation and rod-in-tube technologies. The thermal stability and optical refractive index of the core and cladding glasses were determined by DTA and optical coupler, respectively. The average background loss of tellurite glass fiber was 1.8 dB/m at 1310 nm. Optical microscopy and field emission scanning electron microscope （FESEM） were used to study structural characteristics of preforms and optical fibers. The main loss of tellurite glass fiber could be attributed to scatter centre due to core-cladding interface defects. The amplifier performance of tellurite glass fiber was investigated by pumping with 980 nm laser diode （LD）. The gain coefficient and maximum signal gain were 0.21 dB/mW and 10 dB, respectively, for a pumping power of 120 mW. Gains exceeding 5 dB were obtained over 30 nm bandwidth from 1535 to 1565 nm. The minimum noise figure was 4.8 dB at 1557 nm.     

Fabrication and gain performance of Er~(3 )/Yb~(3 )-codoped tellurite glass fiber

Er3 /Yb3 -codoped TeO2 -ZnO-BaO-La2O3 tellurite glass fiber was fabricated by rotation and rod-in-tube technologies. The ther-mal stability and optical refractive index of the core and cladding glasses were determined by DTA and optical coupler, respectively. The av-erage background loss of tellurite glass fiber was 1.8 dB/m at 1310 nm. Optical microscopy and field emission scanning electron microscope (FESEM) were used to study structural characteristics of preforms and optical fibers. The main loss of tellurite glass fiber could be attributed to scatter centre due to core-cladding interface defects. The amplifier performance of tellurite glass fiber was investigated by pumping with 980 nm laser diode (LD). The gain coefficient and maximum signal gain were 0.21 dB/mW and 10 dB, respectively, for a pumping power of 120 mW. Gains exceeding 5 dB were obtained over 30 nm bandwidth from 1535 to 1565 nm. The minimum noise figure was 4.8 dB at 1557 nm.     

Optimization of synthesis of upconversion luminescence material NaYF4：Er^3＋,yb^3＋ nanometer-phosphor by low-temperature combustion synthesis method

A kind of Er3+-Yb3+ co-doped natrium yttrium fluoride nanometer-phosphor sensitive to 980 nm was synthesized by the low-temperature combustion synthesis method, which expanded the application range of the low-temperature combustion synthesis (LCS) method which is always used in the synthesis of oxides and compound oxides. The synthesis conditions were optimized with orthogonal experiments and the optimum technological parameters were obtained. Intense upconversion emissions at 522, 540 and 653 nm corresponding to the 2H11/2, 4S3/2, and 4F9/2 transitions to the 4I15/2 ground state were observed when excited by continuous wavelength (CW) laser radiation at 980 nm. The effect of the carbamide amount on the phase formation and the luminescence intensity was analyzed. The average particle size of the sample was 30-40 nm.     

Study on Growth and Spectra Properties of Nd: GGG Crystal

The laser crystal Nd GGG was grown by Cz method. The optimum processing parameter is that the pulling rate is 2~4mm·h-1, the rotation rate is 20~40 r·min-1 and the cooling rate is 20℃. The absorption and fluorescence spectra of Nd GGG were measured. The main absorption peak of Nd GGG is at 808 nm and the fluorescence emission peak is at 9430cm-1, corresponding to 4F3/2-4I11/2 emission band of Nd3 ions.     

Energy transfer and frequency upconversion in Er~（3＋）-Yb~（3＋） codoped oxy-fluoro-tungstosilicate glasses

Er3+-Yb3+ codoped oxy-fluoro-tungstosilicate glasses with infrared-to-visible frequency upconversion luminescence were prepared by melting quenching in air.The effects of Er3+ doping on the optical properties of the samples were measured by means of techniques such as optical absorption spectra and photoluminescence spectra.The results showed that intense green and red signals centered at 546 and 665 nm,corresponding to the 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ by a multiphoton stepwise phonon-assisted excited-state absorption process,respectively,were simultaneously observed by exciting the samples with a diode laser operating at 980 nm at room temperature.The upconversion process was found very sensitive to Er3+ content at a constant Yb2O3 content of 5 mol.%.With the increase of Er3+ content from 0.5% to 1.5%,the upconversion intensity increased gradually.Further increasing of Er3+ content to 3.0% resulted in a significant fluorescence quenching.Moreover,the possible upconversion mechanisms were discussed based on the energy-matching conditions and the quadratic dependence on excitation power.     

Preparation and Upconversion Luminescence of Y3Al5O12 ： Yb^3＋ , Er^3＋ Trapsparent Ceramics

YAG： 1% （atom fraction） Yb^3＋ , 0.5% （atom fraction） Er3＋ transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of ^2H11/2→^4I15/2, ^4S3/2→^4I15/2, and ^4F9/2→^4I15/2 of Er^3＋ ions, respectively.     

Luminescence properties of calcium tungstate activated by lanthanide(Ⅲ) ions

Calcium tungstate phosphors activated by the Ln3+ ions(Ln=Pr, Nd, Tb, Yb) were synthesized by a traditional high-temperature solid-state method. The crystal structures and morphologies of the products were characterized by scanning electron microscopy(SEM), X-ray powders diffraction(XRD) and infrared spectra(FT-IR). The samples were found to show luminescence properties(down-conversion, DC, at excitation wavelength 254 nm and up-conversion, UC, at excitation wavelength 980 nm). CaWO4 doped with Tb3+/Yb3+ showed green DC and UC luminescence characteristic of Tb(III) ion in the range of 470–660 nm, corresponding to the 5D4→7F6,5,4,3,2 electronic transition. CaWO4 doped with Pr3+/Yb3+ showed week blue, green and red(DC and UC) luminescence of Pr(III) ion, in the wavelength region of 450–700 nm. Emission peaks were ascribed to the 3P1→3H4,5,6, 3P0→3H4,5,6, 3P1→3F2 and 3P0→3F2 transitions, respectively. CaWO4 doped with Nd3+/Yb3+ phosphor emitted orange UC luminescence at 450–690 nm(2P3/2→4I15/2, 4G7/2→4I9/2,11/2,13/2) and strong near-infrared UC luminescence at 720–900 nm(4F7/2+4S3/2→4I9/2, 4F5/2+2H3/2→4I9/2, 4F3/2→4I9/2) which is the characteristic of Nd(III) ion.     

First-principles study of electronic structure and optical properties of Er:Lu2O3

In the present computational study,we found that Er:Lu₂O₃materials have promise for application in laser applications.The crystal structure and the electronic and optical properties of Er:Lu₂O₃materials were studied using first-principle calculations under the framework of density functional theory.Based on the experimental and calculated results,the structure of Lu₂O₃was established.The calculated results show that doping by Er³⁺can effectively improve its absorption coefficient in the ultraviolet region and improve the static dielectric constant of Lu₂O₃.As the doping concentration of Er³⁺increases,the energy of the valence band electrons excited to the conduction band decreases,and the transition is more likely to occur.The absorption coefficient,reflectance,and electron energy loss spectroscopy are bathochromic shifted.The Lu_2-xEr_xO₃(02O₃.     

Preparation and Upconversion Luminescence of Y3Al5O12∶Yb3+, Er3+ Transparent Ceramics

YAG:1% (atom fraction) Yb3 , 0.5% (atom fraction) Er3 transparent ceramics were fabricated by the solid state reaction method using high-purity Y2O3, Al2O3, Yb2O3, and Er2O3 powders as starting materials. The mixed powder compact was sintered at 1760 ℃ for 6 h in vacuum and annealed at 1500 ℃ for 10 h in an air atmosphere. The ceramics consisted of about 10 μm grains and exhibited a pore-free structure. The optical transmittance of the ceramics at 1064 nm was nearly 80%. Upconversion emissions were investigated on the ceramics pumped by a 980 nm continuous wave diode laser, and strong green emission centered at 523 and 559 nm and red emission centered at 669 nm were observed, which originated from the radiative transitions of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 of Er3 ions, respectively.     

降低供电系统线损提高电能利用率

本文通过对线损的概念、产生原因、如何计算进行阐述,从技术降损和管理线损两个方面提出了降低线损的措施,使线损率长期保持在4%以下,提高了电能利用率。     

谈包钢电网线损管理措施

根据包钢电网的特点和实例分析,采取理论线损计算和分析方法,在计量装置配置、运行方式、电网改造等方面提出并实施了降低包钢电网线损的一些措施。     

企业无形资产流失的探讨

从理论上讨论防止企业无形资产大量流失问题,分析了造成无形资产大量流失的内部原因和外部原因,并从多角度提出防止无形资产大量流失的管理构架.     

变频器瞬间失电过渡的实现

包钢焦化厂新回收系统的鼓风机因电网瞬间失压停机给公司生产造成很大损失,本文着重介绍了对进口的鼓风机变频调速系统实现瞬时断电不停机过渡的技术改造方案及实施的效果。     

采矿损失贫化管理的探讨

采矿损失率和矿石贫化率是表征一个矿山企业采矿技术水平和管理水平的重要参数。通过焦家金矿的历史数据透视，分析了矿产资源开采中损失贫化大的根源，并提出了解决损失贫化大的有效途径：选择合理的采矿方法，制定并执行可行的管理制度，严格执行《矿产资源法》，确定合理的采矿经济技术指标。     

钢坯氧化烧损影响因素试验研究

通过在实验室进行不同加热温度、不同加热气氛对钢坯试样氧化烧损影响研究试验，找出造成钢坯氧化烧损加剧的温度区间及适宜加热气氛，为现场的生产操作提供参考，降低钢坯的氧化烧损率。     

热轧加热炉氧化烧损测定和分析

通过对热轧厂两座加热炉的燃烧系统、氧化烧损进行的热工测试、分析，找出造成炉子氧化烧损严重的原因，并给出相应措施。     

Mourning the loss of a child who has not died.

This article presents material from the treatment of a woman who experienced her living son as dead. This fantasy is interpreted both as a response to and defense against the trauma of loss. Shattered expectations and insecure attachment immure her in a relationship in which hope leads repeatedly to affective dysregulation and crushing disappointment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical status as a moderator of depressive symptoms among older adults with dual sensory loss.

Objective: This study evaluated the ability of three measures of physical status—physical activity, physical condition, and body mass index (BMI)—to moderate the relationship between dual sensory loss (DSL) and depressive symptoms in older adults. Method: Nationally representative longitudinal data were used to develop multilevel models predicting depressive symptoms among two groups of older adults, 1380 who developed DSL during the study and 1308 without sensory loss. Results: All three measures were associated with depressive symptoms for persons who had or would develop a DSL: participation in physical activity and being in better physical condition were associated with lower levels of depressive symptoms, while lower BMI levels were associated with higher levels of depressive symptoms. All moderator variables had a larger effect for persons with DSL as compared to persons without sensory loss. Implications: The implication of these findings is that participation in a regular program of physical activity may provide multiple benefits to older persons with DSL. Families and health care providers can offer support for being physically active by ensuring the person has the best possible correction for the sensory losses, providing encouragement, and/or providing physical assistance with exercise. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

加热炉氧化烧损原因与对策分析

就加热炉加热过程中氧化铁皮的形成机理及影响因素进行了论述，并介绍了目前国内解决氧化烧损所采取的一些有益的方法。