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.     

Frequency Upconversion Emission of Er^3＋-Doped Strontium-Lead-Bismuth Glasses

Er^3 -doped strontium-lead-bismuth glasses for developing potential upconversion lasers have been fabricated and characterized. Under 975 nm excitation, intense green and red emissions centred at 525, 546, and 657nm,corresponding to the transitions ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2, and ^4F9/2 → ^4I15/2, respectively, were observed at room temperature. The upconversion mechanisms are discussed based on the energy matching and quadratic dependence on excitation power, and the dominant mechanisms are excited state absorption and energy transfer upconversion for 525 and 546nm emissions, and energy transfer upconversion for 657nm emission.     

Visible Upconversion Emission in Er3＋—Doped GeO2—PbO—PbF2 Glass

The upconversion fluorescence emission of Er3 -doped 60GeO2-2OPbO-2OPbF2 glass was experimentally investigated under the pump of 976-nm laser diode. The results reveal the existence of intense emission bands centred around 524, 545, and 657nm at room temperature. The green emission at 524 and 545nm is due to the 4S3/2 2 Hll/2→ 4I15/2 transition and the red emission of 657nm originates from the 4F9/2-→4I15/2 transition of Er3 . The quadratic dependence of the green and red emissions on excitation power indicates that a two-photonabsorption process occurs under the 976-nm excitation. The excited- state absorption from 4I ll/2 and the cross relaxation between two Er3 ions in the 4I ll/2 state contribute to the green emission. The red emission at 657nm is attributed to the excited-state absorption and cross relaxation processes in the 4I13/2 level as well as the 4S3/2 level nonradiative transition of Er3 .     

Structural and Upconversion Fluorescence Properties of Er^3＋／Yb^3＋-Codoped Lead-Free Germanium-Bismuth Glass

We study the structural and infrared-to-visible upconversion fluorescence properties of Er^3 /yb^3 -codoped leadfree germanium-bismuth glass. The structure of lead-free germanium-bismuth-lanthanum glass is investigated by peak-deconvolution of F~aman spectroscopy. Intense green and red emissions centred at 525, 546, and 657nm,corresponding to the transitions ^2H11/2 → 4I15/2, ^4S3/2 → 4I15/2, and 4F9/2 → 4I15/2, respectively, are observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975nm excitation.     

High Efficiency Infrared-to-Visible Upconversion Emission in Er^3＋,Yb^3＋, and Ho^3＋ Codoped Tellurite Glasses

A novel method of codoping the Er^3＋, Yb^3＋, and Ho^3＋ ions in tellurite glasses is demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Three intense emission bands observed in Er^3＋, Yb^3＋, and Ho^3＋ codoped tellurite glasses centred at 525, 547, and 657nm correspond to Er^3＋： ^2H11/2 -4 ^4I15/2, Er^3＋： ^4S3/2 →^4I15/2＋Ho^3＋： ^5S2（^5F4） → ^5Is, and Er^3＋： ^4Sa/2 → ^4I15/2＋Ho^3＋： ^5F5 → ^5Is transitions, respectively. No visible upconversion quenching phenomenon is observed when three rare-earth ions are codoped together in tellurite glasses. In contrast, the upconversion intensity of red and green emissions in Er^3＋, Yb^3＋, and Ho^3＋ codoped glasses is enhanced largely when compared with Er^3＋ /Yb^3＋-codoped glasses. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The three emissions are based on two-photon absorption processes.     

Frequency Upconversion Fluorescence Emission of Er^3＋-Doped Oxychloride Germanate Glass

Frequency upconversion fluorescence property of Er^3 -doped oxychloride germanate glass is investigated. Intense green and red emissions centred at 525, 546, and 657nm, corresponding to the transitions ^2H11/2→4I15/2,^4S3/2→^4I15/2, and ^4F9/2→^4I15/2, respectively, were simultaneously observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm laser diode (LD) excitation. The Raman spectrum investigation indicates that oxychloride germanate glass has the maximum phonon energy at-805cm^-1. The thermal stability of this oxychloride germanate glass is evaluated by differential scanning calorimetry, and thermal stability factor AT(△T = Tx -Tg) is 187℃. Intense upconversion luminescence and good thermal stability indicate that Er^3 -doped oxychloride germanate glass is a promising upconversion laser material.     

Intense frequency upconversion fluorescence of Er3+/Yb3+ co-doped lithium-strontium-lead-bismuth glasses

Infrared-to-visible upconversion fluorescence of Er3+/Yb3+ co-doped lithium-strontium-lead-bismuth (LSPB) glasses for developing potential upconversion lasers has been studied under 975-nm excitation.Based on the results of energy transfer efficiency and upconversion spectra, the optimal Yb3+-Er3+ concentration ratio is found to be 5∶1. Intense green and red emissions centered at 525, 546, and 657 nm,corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2 → 4I15/2, respectively, were observed. 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. The high-populated 4I11/2 level is supposed to serve as the intermediate state responsible for the upconversion processes. The intense upconversion luminescence of Er3+/Yb3+ co-doped LSPB glasses may be a potentially useful material for developing upconversion optical devices.     

Upconversion Luminescence Dynamics in Er^3＋/Yb^3＋ Codoped Nanocrystalline Yttria

The upconversion luminescence and dynamics in Er^3＋ /Yb^3＋ codoped nanocrystalline yttria （7-65 nm） are studied under 980-nm pulsed laser excitation, It is found that the red emission of ^4F9/2-^4I15/2 and the green emission of ^2H11/2/^4S3/2 in nanoparticles with lower concentration of Yb^3＋ result from a two-photon excitation, In nanocrystals with higher Yb^3＋ concentration, the red emissions from a two-photon excitation, while the green emissions from a three-photon excitation, The luminescence dynamics indicates that as the particle size decreases, both the rise and the decay time constants become shorter, As the size decreases to several nanometres, the rise process nearly disappears, suggesting that the upconversion luminescence originates mainly from self-excitation of Er^3＋, instead of the energy transfer of Yb^3＋→ Er^3＋.     

Intense frequency upconversion fluorescence of Er~(3+)/Yb~(3+) co-doped lithium-strontium-lead-bismuth glasses

Infrared-to-visible upconversion fluorescence of Er3+/Yb3+ co-doped lithium-strontium-lead-bismuth (LSPB) glasses for developing potential upconversion lasers has been studied under 975-nm excitation. Based on the results of energy transfer efficiency and upconversion spectra, the optimal Yb3+-Er3+ concentration ratio is found to be 5:1. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H11/2→4 I15/2, 4S3/2→4 I15/2, and 4F9/2→4 I15/2, respectively, were observed. 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. The high-populated 4I11/2 level is supposed to serve as the intermediate state responsible for the upconversion processes. The intense upconversion luminescence of Er3+ /Yb3+ co-doped LSPB glasses may be a potentially useful material for developing upconversion optical devices.     

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.     

Host dependent frequency upconversion of Er-doped oxyfluoride germanate glasses

Er³⁺-doped oxyfluoride germanate glasses have been synthesized by the conventional melting and quenching method. The Judd-Ofelt intensity parameters were calculated based on the Judd-Ofelt theory and absorption spectra measurements. With the substitution of PbF₂ for PbO, the Ω₂ parameter decreases, while the Ω₆ parameter increases. These change trends indicate that fluoride anions come to coordinate erbium cations and the covalency of the Er-O bond decreases. Structural and thermal stability properties were obtained by Raman spectra and differential thermal analysis, indicating that PbF₂ plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. 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 simultaneously observed at room temperature. With increasing PbF₂ content, the intensity of red (657 nm) emissions increases significantly, while that of the green (525 and 546 nm) emission increases slightly. The results indicate that PbF₂ has more influence on the red (657 nm) emission than the green (525 and 546 nm) emissions in oxyfluoride germanate glasses. The possible upconversion luminescence mechanisms have also been estimated and discussed.     

Composition dependent frequency upconversion luminescence in Er-doped oxychloride germanate glasses

Er³⁺-doped oxychloride germanate glasses have been synthesized by conventional melting and quenching method. Structural and thermal stability properties were obtained based on the Raman spectra and differential thermal analysis, indicating that PbCl₂ plays an important role in the formation of glass network and has an important influence on the maximum phonon energy and thermal stability of host glasses. 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. With increasing PbCl₂ content, the intensity of green (525 and 546 nm) emissions increases significantly, while the red (657 nm) emission increases slowly. The results indicate that PbCl₂ has more influence on the green emissions than the red emission in oxychloride germanate glasses. The possible upconversion luminescence mechanisms has also been estimated and discussed.     

Tunable upconversion in Er-doped orthorhombic lead fluoride compound

Near infrared-visible upconversion in Er³⁺ doped orthorhombic PbF₂ compound is investigated. It is experimentally observed that the red emission intensity increases monotonously with Er³⁺ concentration increase, while the green emission intensity first increases and then decreases. Based on the rate-equation, the energy transfers involved in the upconversion processes have been explored. It is shown that due to the different multipolar nature for the energy transfer processes of ²H_11/2 (⁴S_3/2)+⁴I_15/2→⁴I_9/2+⁴I_13/2 and ⁴I_11/2+⁴I_11/2→⁴F_7/2+⁴I_15/2, the green and red upconversion emissions depend on Er³⁺ concentration in different ways. The theoretical results are in good agreement with the experimental observation. It is shown that the upconverted emission bands can be tuned by controlling Er³⁺ concentration in orthorhombic PbF₂ compound, which has many photonic applications under NIR excitation.     

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.     

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.     

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     

Thermal stability and spectroscopic properties of Er-doped lead fluorogermanate glasses

The thermal characterization and spectroscopic properties of Er³⁺-doped 0.6GeO₂-(0.4-x)PbO-xPbF₂ glasses were investigated experimentally. With the replacement of PbO by PbF₂ the thermal stability of glasses is improved and the infrared fluorescence intensity at 1530 nm is increased. The Judd-Ofelt intensity parameters, radiative transition rates, and fluorescence lifetimes of the excited ⁴I_13/2 level of Er³⁺ ions were calculated from Judd-Ofelt theory. The asymmetric ligand field around Er³⁺ ions resulted from the incorporation of PbF₂ into germanate glasses, broadens the infrared emission spectra at 1530 nm. Upconversion luminescence in the investigated glasses was observed at room temperature under the excitation of 976 nm laser diode. The glass 0.6GeO₂-0.3PbO-0.1PbF₂ exhibits the maximum upconversion emission intensity, while no frequency upconversion luminescence was observed in the 0.6GeO₂-0.4PbO glass. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption contributes to the visible emission under the 976-nm excitation.     

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     

Near infrared to visible upconversion of Er in CaZrO3/CaSZ eutectic crystals with ordered lamellar microstructure

In this work we report the near infrared to visible upconversion luminescence of Er³⁺ ions in CaZrO₃/CaSZ eutectic crystals with ordered lamellar microstructure. The microstructure consists of alternating 2-μm-thick lamellae of calcia-stabilized zirconia (CaSZ) and calcium zirconate (CaZrO₃) single crystals. Er³⁺ ions enter both phases but at a higher concentration in CaSZ. Wavelength selective excitation along the ⁴I_15/2→⁴I_9/2 absorption band allows to distinguish the upconverted emission from Er³⁺ sites in the two eutectic phases. In the CaZrO₃ phase the upconversion emission spectrum is dominated by an intense green emission characterized by sharp (²H_11/2,⁴S_3/2) levels together with a more weak red emission from ⁴F_9/2 level. In the CaSZ phase, a broad green and red emissions occur with an enhancement of the red emission from level ⁴F_9/2. These upconverted emissions are attributed to a two photon process. The excitation wavelength dependence of the upconverted luminescence together with its time evolution after infrared pulsed excitation suggest that energy transfer upconversion processes are responsible for the upconversion luminescence.