Er3+离子掺杂钡镓锗玻璃上转换发光机理研究

研究了Er³⁺离子掺杂钡镓锗玻璃的吸收光谱、拉曼光谱和上转换光谱.分析了Er³⁺离子在钡镓锗玻璃中的上转换发光机理.结果表明：玻璃的最大声子能量为828cm^-1，紫外截止波长为275nm.采用800nm和980nmLD激发玻璃样品，在室温下观察到强烈的上转换绿光和红光发射.随着Er³⁺离子浓度的增加，绿光发光强度先增加后减小，而红光发光强度呈单调递增趋势.能量分析表明：800nmLD激发产生的绿光主要源于Er³⁺离子4I_13/2能级的激发态吸收过程；红光发射主要源于Er³⁺离子4I_13/2能级与4I_11/2能级之间的能量转移过程.980nmLD激发产生的绿光主要源于Er³⁺离子4I_11/2能级之间的能量转移过程；而红光发射主要源于Er³⁺离子4I_13/2能级与4I_11/2能级之间的能量转移过程和4I_13/2能级的激发态吸收过程.通过量子效率分析，发现采用800nmLD激发Er³⁺离子掺杂浓度为1mol% 的样品时，上转换绿光发光效率最高. 关键词： 上转换发光机理 3+离子掺杂')" href="#">Er³⁺离子掺杂 钡镓锗玻璃     

Upconversion luminescence in Er-doped germanate-oxyfluoride and tellurium-germanate-oxyfluoride transparent glass-ceramics

Upconversion luminescence has been studied for Er³⁺ in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from ⁴S_3/2 state and a weaker red emission centered at 662 nm from ⁴F_9/2 state generally seen from Er³⁺-doped glasses, a violet emission centered at 410 nm from ²H_9/2 state and a near-ultra-violet emission centered at 379 nm from ⁴G_11/2 state were also observed from transparent glass-ceramics. The upconversion luminescence of Er³⁺ ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er³⁺ ions were incorporated into the precipitated β-PbF₂ nanocrystals.     

A spectroscopic investigation of Y 3 Al 5 O 12 :Pr 3 + in translucent ceramic form: Crystal field analysis assisted by configuration-interaction

This paper presents an investigation of Pr³⁺ doped in the D₂ site of Y₃Al₅O₁₂ (YAG), for the first time on a translucent ceramic sample free of spurious phases, impurity or pair sites. The optical study is carried out by optical absorption, excitation, and emission by selective excitation into ¹D₂ and ³P₀, at different temperatures between 20 K and 60 K, in the 4 300-23 000 cm^-1 range. A detailed account of the line assignments is given. 67 over 91 levels of the 4f² configuration are determined. Several crystal field calculations within the ground configuration 4f² and the larger matrix 4f^2+4f6p are carried out. The energy level fit is slightly improved by configuration interaction. The ³P₂ and ¹I₆ levels are strongly mixed together by the large 6th order crystal field parameters. In sintered samples with different Pr³⁺ concentrations, satellite lines with intensities increasing quadratically with the concentration are observed. A few weak lines forbidden in D₂ site symmetry are observed. Received 9 November 2001 and Received in final form 8 February 2002     

Ultraviolet upconversion in Pr3+:Y2SiO5 crystal by Ar+ laser (488 nm) excitation

Ultraviolet upconversion fluorescence band (260–350 nm) has been observed from Pr³⁺:Y₂SiO₅ pumped by Ar⁺ ion laser (488 nm). Power dependence of the fluorescence emitted from 4f5d, ³P₀ and ¹D₂ were measured. The upconversion mechanism was analyzed using the rate equations with a simplified three level model. It appears that excited state absorption (ESA) is the dominant upconversion process for lower Pr³⁺ concentration and energy transfer upconversion (ETU) is dominant for higher Pr³⁺ concentration.     

Er,Yb:YAG微晶玻璃发光特性的研究

高温熔制Er³⁺，Yb³⁺离子掺杂CaO-Y₂O₃-Al₂O₃-SiO₂系统玻璃，并进行微晶化处理，研究了微晶玻璃中Er³⁺离子的发光及上转换发光特性，分析了微晶玻璃上转换发光机理.结果表明：原始玻璃经热处理得到了Er,Yb:YAG微晶玻璃，微晶玻璃中Er³⁺离子在室温下⁴I_13/2→⁴I_15/2跃迁产生横盖1450—1650nm区间的超宽带荧光，荧光半高宽达180nm，这可能由于YAG微晶相中Er³⁺离子与玻璃相中残留Er³⁺离子的共同发光；Er³⁺与Yb³⁺离子局域基质声子能量的降低使微晶玻璃Er³⁺离子上转换发光强度与原始玻璃相比显著提高，绿光、红光上转换荧光强度比玻璃样品分别增强约7和3倍；微晶化后Er³⁺，Yb³⁺离子局域环境发生变化也导致微晶玻璃中Er³⁺离子绿光、红光上转换发光相对强度发生变化. 关键词： 铒 镱:钇铝石榴石 微晶玻璃 荧光光谱     

Kinetics of Er3+-doped fluorozirconate optical fiber upconversion fluorescence and laser emission under 800 nm excitation

Applying single- and double-pulse excitation at 800 nm, the kinetics of the upconversion fluorescence in the green, as well as the upconversion laser at 543 nm was studied. No significant delay between the pumping pulse and the laser emission was found. In the erbium doped (1000 ppm) optical fiber, the mechanism responsible for the upconversion is purely of the excited state absorption (ESA) type. The double-pulse technique enables also a determination of the lifetime of the intermediate metastable state ⁴ I _11/2 (7±0.3 ms). Some other basic properties of the upconverted fluorescence and of the laser itself (fluorescence spectrum, optical gain, laser threshold) are also described. Received: 11 December 2000 / Revised version: 18 February 2001 / Published online: 18 July 2001     

Upconversion fluorescence property of Er/Yb-codoped novel bismuth-germanium glass

Infrared-to-visible upconversion fluorescence property of Er³⁺/Yb³⁺-codoped novel bismuth-germanium glass under 975 nm LD excitation has been studied. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. The structure of the bismuth-germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel bismuth-germanium glass with low maximum phonon energy (∼750 cm⁻¹) can be used as potential host material for upconversion lasers.     

Upconversion studies in Er doped TeO2-M2O (M=Li, Na and K) binary glasses

The luminescence properties of Er³⁺ doped alkali tellurite [ TeO₂-M₂O (M=Li, Na and K)] glasses are investigated. Infrared to visible upconversion emissions are observed at 410, 525, 550 and 658 nm using 797 nm excitation. These bands are assigned to the ²H_9/2  →⁴I_15/2, ²H_11/2  →⁴I_15/2, ⁴S_3/2  →⁴I_15/2, ⁴F_9/2  →⁴I_15/2 transitions of Er³⁺ respectively. Detailed study reveals that the ²H_9/2  →⁴I_15/2 transition at 410 nm involves a three-step process while the other transitions involve two-steps. Excitation with 532 nm radiation gives additional bands at 380, 404, 475 and 843 nm wavelengths due to the ⁴G_11/2  →⁴I_15/2, ²P_3/2  →⁴I_13/2, ²P_3/2  →⁴I_11/2, and ⁴S_3/2  →⁴I_13/2 transitions, respectively, along with the bands observed on NIR excitation. The fluorescence yield is found to be largest for the TeO₂-Na₂O glass. The lifetime of the ⁴S_3/2 level has been measured for all the three cases and used to explain the upconversion mechanisms. The fluorescence intensity ratio corresponding to the two thermally coupled levels (²H_11/2, ⁴S_3/2) has been used to estimate the temperature of the glass. It is observed that the temperature sensing capacity of TeO₂-Li₂O glass is better than the other two glasses.     

Enhancement of upconversion intensity in Er3+ doped tellurite glass in presence of Yb3+

TeO₂–PbO glasses doped/codoped with Er³⁺/Er³⁺-Yb³⁺ ions have been fabricated by melting and quenching method. Efficient frequency upconversion emissions spanning from blue to red regions corresponding to the ²H_11/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions, respectively, upon excitation with 976 nm diode laser radiation have been observed. The variations observed in the intensity of whole upconversion emission spectra due to the presence of the Yb³⁺ ions are reported and discussed in detail.     

Structural and upconversion fluorescence properties of Er/Yb-codoped oxychloride lead-germanium-bismuth glass

Structural and infrared-to-visible upconversion fluorescence properties of Er³⁺/Yb³⁺-codoped oxychloride lead-germanium-bismuth glass have been studied. The Raman spectrum investigation indicates that PbCl₂ plays an important role in the formation of glass network, and has an important influence on the upconversion luminescence owing to lower phonon energy. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation.     

Ultraviolet upconversion luminescence in Er-doped Y2O3 excited by 532 nm CW compact solid-state laser

Ultraviolet upconversion emissions at 262, 276, 308 and 320 nm were observed from Er³⁺-doped Y₂O₃ with a 532 nm continuous wave compact solid-state laser excitation. Power-dependence analysis demonstrates that two-photon upconversion process populates the ⁴D_5/2, ²H_9/2 and ²P_3/2 states. The energy transfer upconversion (ETU) plays an important role in populating ⁴D_5/2 and ²P_3/2 states. It appears that ²P_3/2 state population originates from ETU ²H_11/2+²H_11/2→⁴I_13/2+²P_3/2, moreover, a subsequent excited state absorption (ESA) from the ⁴I_9/2 level.     

Host dependent thermal stability and frequency upconversion of Er^3＋-doped heavy metal oxyfluoride germanate glasses

The upconversion properties of Er^3＋-doped heavy metal oxyfluoride germanate glasses under 975 nm excitation have been investigated. The intense green （551 and 529 nm） and relatively weak red （657 nm） emissions corresponding to the transitions ^4S3/2→^4I15/2, ^2H11/2→^4 I15/2 and ^4F9/2 →^4I15/2, respectively, were simultaneously observed at room temperature. The content of PbF2 has an important influence on the upconversion luminescence emission. With increasing content of PbF2, the intensities of green （529 nm） and red （657 nm） emissions increase slightly, while the green emission （551 nm） increases markedly. These results suggest that PbF2 has an influence on the green （551 nm） emission more than on the green （529 nm） and red （657 nm） emissions.     

Ab initio calculation of excited state dipole polarizability - Application to the first 1, 3 Σ + g,u states of Li 2

Firstly, imaginary frequency-dependent dipole polarizabilities of Li in its ² S ground state and the first ² P excited state are calculated from a time-dependent gauge-invariant method using effective core pseudo-potentials and the multi-configuration one-electron wave function. C₆ dispersion coefficients of the 2 s + 2 s and 2 s + 2 p dissociations are deduced and also compared with all-electron values. Then, static polarizabilities of Li₂ in its ground and first excited ^{1, 3} Σ ⁺ _g,u states are obtained at interatomic distance corresponding to the energy minimum of each state. Received 10 May 2001 and Received in final form 14 September 2001     

Infrared to visible upconversion luminescence in Er3+/Yb3+ doped titanate glass prepared by containerless processing

Er³⁺ doped TiO₂–La₂O₃ glasses modified by ZrO₂ have been successfully fabricated by the containerless method with incorporated Yb³⁺ ions as sensitizers. Under the excitation of 980 and 808 nm diode lasers, visible emissions centered at 534, 554 and 674 nm are observed, which are assigned to the Er³⁺ transitions of ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2, respectively. The emission signals are so strong that they can be observed by naked eyes even at pumping power as low as 20 mW. Measurements of pump-power dependent intensity and time-resolved decay behavior of upconversion luminescence show that two-photon excited state absorption (ESA) and energy transfer (ET) between rare earth ions are the predominant mechanisms for upconversion emissions. Besides, the intensity of upconversion luminescence has been enhanced by increasing the concentration of ZrO₂ in these rare earth doped bulk titanate glasses.     

Laser-diode excited intense upconversion luminescence of Er^3＋ in bismuth-lead-germanate glasses

We have investigated infrared-to-visible upconversion luminescence of Er^3＋ in bismuth-lead-germanate glasses. The UV cutoff wavelength is shortened while its lifetime is increased almost linearly, with PbF2 substituting for PbO in the bismuth-lead germanate glasses. Three emissions centred at around 529, 545 and 657 nm are clearly observed, which are identified as originating from the ^2H11/2→^4 I15/2,^4S3/2→^4 I15/2 and ^4 F9/2 →^4 I15/2 transitions, respectively. It is noted that all the upconversion emission intensities increase with PbF2 concentration increasing. The ratio between the intensities of red and green emissions increases with the increasing of PbF2 content. Energy transfer processes and nonradiative phonon-assisted decays account for the populations of the ^2 H11/2,^4 S3/2 and ^4F 9/2 levels. The quadratic dependence of fluorescence on excitation laser power confirms a two-photon process to contribute to the upconversion emissions.     

掺铒矾酸钇晶体上转换荧光研究

使用波长为808和658nm的半导体激光器和染料激光器作为激发源，测量了Er³⁺：YVO₄晶体的波长在553和410nm附近的上转换荧光.对激发过程的分析表明，贡献于上转换荧光的主要激发机制为激发态吸收.在不同浓度下对上转换荧光的寿命测量结果显示，随Er³⁺浓度的提高，553nm绿光的荧光寿命随浓度的增加而减小，但410nm的荧光寿命随Er³⁺浓度无明显变化.结合绿光强度随掺杂浓度增加而减小的结果，认为在所测浓度范围内 关键词：     

980 nm激发下Er3+/Yb3+共掺杂ZrO2-Al2O3粉末的上转换发光特性

通过固相反应法制备了Er³⁺/Yb³⁺共掺杂ZrO₂-Al₂O₃粉末的样品，并对样品在980nm激光激发下的上转换发光特性进行了研究.从发射光谱可以发现，在可见光范围内有3个强的发光带，一个位于654nm附近的红光带和两个分别位于545nm、525nm附近的绿光带，分别对应于Er³⁺离子的以下辐射跃迁：⁴F_9/2→⁴I_15/2、⁴S_3/2→⁴I_15/2、 ²H_11/2→⁴I_15/2.其中又以Er³⁺离子的⁴F_9/2→⁴I_15/2跃迁产生的红色荧光辐射最强.对其上转换发光机制进行了分析，发现这三个发光过程都是双光子过程.对样品粉末进行了XRD检测，发现ZrO₂主要以立方相为主，并且计算得到了这种立方结构的晶格常数.Al₂O₃固溶于ZrO₂中，Al³⁺嵌入ZrO₂后产生氧空位，导致ZrO₂晶体的对称性降低，这种结构变化更有利于提高上转换效率，即上转换发光强度增强. 关键词： 3+/Yb³⁺')" href="#">Er³⁺/Yb³⁺ 上转换 2-Al₂O₃')" href="#">ZrO₂-Al₂O₃ 荧光 稀土     

应用于白光显示的Tm3+/Ho3+/Yb3+共掺碲酸盐玻璃上转换发光特性研究

用高温熔融法制备了Tm³⁺/Ho³⁺/Yb³⁺共掺碲酸盐玻璃(TeO₂-ZnO-La₂O₃)样品,测试了玻璃样品的吸收光谱和上转换发光光谱,分析了上转换发光机理.结果发现:在975 nm波长激光二极管(LD)激励下,制备的碲酸盐玻璃样品可以观察到强烈的红光(662 nm)、绿光(546 nm)和蓝光(480 nm)三基色上转换发光,红光对应于Tm³⁺离子 关键词： 碲酸盐玻璃 上转换发光 白光 3+/Ho³⁺/Yb³⁺共掺')" href="#">Tm³⁺/Ho³⁺/Yb³⁺共掺     

Nonlinear blue upconversion luminescence in Gd2O3: Er3+/Yb3+ nanowires

Gd₂O₃: Er³⁺/Y b³⁺ nanowires were prepared by a hydrothermal method. The upconversion luminescence was studied with 978-nm excitation. Ultraviolet and blue upconversion luminescence in which thermalization processes were involved, green and red upconversion luminescence were observed respectively. We analyzed the mechanism of upconversion luminescence. According to the ratio of ² H_11/2–⁴I_15/2 emission intensity to ⁴ S_3/2–⁴I_15/2 emission intensity, the temperature of the sample exposed to radiation of 978-nm laser was given.     

Upconversion excitations in Pr<Superscript>3+</Superscript>-doped BaY<Subscript>2</Subscript>F<Subscript>8</Subscript> crystal

We report the orange-to-blue and infrared-(IR)-to-blue wavelengths upconversion luminescence in Pr³⁺:BaY₂F₈ crystals. Mechanism of the orange light upconversion into blue ³P₀ state emission was confirmed to be energy transfer between two Pr³⁺ ions in the ¹D₂ state. IR-to-blue upconversion has only been observed under two different color IR pumping. The first resonant step was the ³H₄→¹G₄ ground state absorption transition, and the second resonant transition was the excited state absorption from the ¹G₄ to ¹I₆ and ³P_J levels. A comparison of the efficiency of the IR-to-blue upconversion in several praseodymium activated host is presented and discussed. A model of the IR pumped upconversion praseodymium blue laser is presented and the population inversion conditions are calculated.