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.     

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.     

Synthesis and optical properties of KZnLa0.99Nd0.01(VO4)2 triple vanadate(V)—New promising laser materials

In an attempt to find a neodymium-vanadate system with long lifetime of ⁴F_3/2 level and relatively strong ⁴F_3/2→⁴I_11/2 emission for laser applications, the optical properties of Nd³⁺ in a new KZnLa(VO₄)₂ host is reported. The crystalline samples were obtained at 900 °C in air. The samples were crystallized in monoclinic system and were isostructural with KZnLa(PO₄)₂. KZnLa_0.99Nd_0.01(VO₄)₂ strongly emits in the near infrared range with the maxima at 871.6 and 1057 nm upon excitation through the ⁴F_5/2 level (808 nm) or by the charge transfer bands of VO₄³⁻. The lifetime of ⁴F_3/2 level of Nd³⁺ ion is larger than that observed in other neodymium-vanadates systems.     

Er3+离子浓度对ZnS:ErF3薄膜交流电致发光特性的影响

本文研究了Er³⁺离子浓度对ZnS:ErF₃薄膜交流电致发光(ACEL)特性的影响。I(⁴F_9/2→⁴I_15/2)受Er³⁺离子浓度的影响较大,随Er³⁺离子浓度增高,I(⁴F_9/2→⁴I_15/2)增强,甚至超过I(²H关键词：     

A comment on “Ab initio study: the potential energy curves and ro-vibrational spectrum of low-lying excited states of HCl+ cation”

Since the ²Π state in HCl⁺ is an inverted doublet, the energy of the ²Π_1/2 state is higher than the ²Π_3/2. Therefore, the larger value of intensity correspond to the transition of ²Π_3/2. We calculated the Einstein A coefficients and radiation lifetimes for the A²Σ⁺-X²Π transition. Our results are in good agreement with the experimental data and theoretical values. Then the ro-vibrational line intensities of the 1-0 band were calculated for the ²Π_3/2 and ²Π_1/2 states of HCl⁺. Employing the RKR potential, the predicted band origins for Δν=1-0 are 2569.3 and 2568.55 cm-1 for ²Π_3/2 and ²Π_1/2, respectively.     

Energy transfer and fluorescence characteristics of erbium-doped ytterbium aluminum garnet

We have examined the fluorescence characteristics of the garnet-type crystal Yb₃Al₅O₁₂ : Er³⁺ (YbAlG : Er³⁺) and studied the energy transfer process between the two rare earth ions over a temperature range 78–297 K. Certain data were compared with those of YAlG : Er³⁺. In YbAlG : Er³⁺, Yb fluorescence is observed at ?1.03 μm (corresponding to the ²F_5/2 → ²F_7/2 transition); Er fluorescence occurs at ?8500 Å (⁴S_3/2 → ⁴I_13/2 transition) and ?1.6 μm (⁴I_13/2 → ⁴I_15/2 transition). In YAlG : Er³⁺, the same Er lines are observed with the addition of a band at ?1 μ (⁴I_11/2→⁴I_15/2 transition). In YbAlG : Er³⁺, the decay pattern of the Yb emission is purely exponential at all the temperatures examined; the fluorescence lifetime ranges from 36 μ s (at 78 K) to 74 μs(at 269 K). The lifetime of the Er⁴I_13/2 level in the same sample increases from 5.4 ms (at 78 K) to 6.85 ms (at 294 K). The lifetime of this Er level in YAlG : Er³⁺ is weakly temperature dependent over the same range with a value of ?12 ms. Excitation spectra were obtained for the Er 1.53 μm fluorescence in YbAlG : Er³⁺ in order to verify the presence of Yb → Er energy transfer in this sample. The presence of the Yb absorption band (?1 μm) in these spectra provides direct evidence of this energy transfer. The relative enhancement of this Yb band with respect to the Er bands in going from 78 K to 175 K is an indication of a more efficient transfer at the higher temperature. Excitation spectra obtained for the Yb 1.03 μm fluorescence in YbAlG : Er³⁺ revealed the presence of Er → Yb energy transfer as well in this sample. The existence of both Yb → Er and Er → Yb transfer is expected, due to the resonance between the ⁴I_11/2 → ⁴I_15/2 transition of Er and the ²F_5/2 → ²F_7/2 transition of Yb. The above results are explained in terms of a rate equation model in which transfer in both directions is treated in the following manner: Yb → Er transfer is considered to be much more probable than decay processes originating at the Yb ²F_5/2 level; Er → Yb transfer is treated as much more probable than decay processes originating at the Er ⁴I_11/2 level.     

Description of negative parity yrast states in156Er

Positive and negative parity yrast states are studied in ₆₈ ¹⁵⁶ Er₈₈ with a particle number projected Hartree-Fock-Bogoliubov method constrained on an average angular momentum. The theory predicts a second anomaly of the positive parity yrast states due to the alignment of ah _11/2 proton pair. The double backbending in the negative yrast band is understood: AtJ ^π=9^? to 11^? it is due to the intersection of the (πg _7/27/2⁺)×(πh _11/27/2^?) and the (πi _13/21/2⁺)×(πh _9/23/2^?) 2q.p. bands. The second backbending found experimentally fromJ ^π=21^? to 23^? is connected with an alignment of ai _13/2 neutron pair of the core in the proton 2q.p. band.     

Visible upconversion and infrared luminescence investigations of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> powders doped with Er<Superscript>3+</Superscript>, Yb<Superscript>3+</Superscript> and Zn<Superscript>2+</Superscript> ions

Alumina (Al₂O₃) powders doped with Er³⁺, Yb³⁺ and Zn²⁺ ions have been prepared by a low-temperature combustion synthesis technique. The phase purity and crystalline structure of the combustion products are confirmed by powder X-ray diffraction. An efficient frequency upconversion in the visible region and the emission in the infrared (IR) region respectively corresponding to the ²H_11/2, ⁴S_3/2→⁴I_15/2, ⁴F_9/2→⁴I_15/2 and ⁴I_13/2→⁴I_15/2 transitions upon direct excitation with a CW laser lasing at ∼980 nm are discussed. The enhancement observed in the intensity of the upconversion emission bands in the visible region and the emission band in the IR region due to the presence of Yb³⁺ and Zn²⁺ in Er³⁺:Al₂O₃ powders is reported and explained in detail.     

Lamb shifts for hydrogen,using the sachs elementary interaction theory

The Lamb shifts of theS _1/2 andP _1/2 states of hydrogen atoms are calculated using the Sachs elementary interaction theory. BothS _1/2 andP _1/2 levels are shifted with respect to the Dirac levels by energies of the same order of magnitude. Agreement with experiment is obtained for the² S _1/2 –² P _1/2 and³ S _1/2 –³ P _1/2 Lamb shifts, but the predicted¹ S _1/2 –² P _1/2 Lamb shift term of 12,164 MHz is in disagreement with the experimental value of 7860 ± 1140 MHz.     

低温下Er3+/Yb3+共掺碲酸盐玻璃的发光特性研究

研究了在8—300K温度范围中, Er³⁺/Yb³⁺共掺碲酸盐玻璃的15μm荧光光谱、上转换光谱与温度的关系. Er³⁺:⁴I_13/2→⁴I_15/2跃迁发射光谱通过高斯拟合和简单的四能级系统估计了Er³⁺离子⁴I_13/2和⁴ 关键词： 碲酸盐玻璃 上转换发光 低温 荧光特性     

Effect of pressure on luminescence properties of Sm3+ ions in potassium niobate tellurite glass

Emission spectra and decay properties of the ⁴G_5/2 level of Sm³⁺ ions in TeO₂+K₂O+Nb₂O₅ glass have been measured as a function of pressure upto 14.6 GPa at room temperature. A progressive red shift in the barycentres of ⁴G_5/2→⁶H_J (J=9/2, 7/2 and 5/2) emission bands and increase in splitting of these bands have been observed with increasing pressure. The luminescence decay profile of the ⁴G_5/2 level at ambient condition shows a nearly single exponential nature and with increase in pressure it becomes gradually non-exponential associated with a decrease in lifetime. The non-exponential decay curves are well-fitted to the Inokuti–Hirayama model for S=6, indicating that the interaction for cross-relaxation energy transfer between Sm³⁺ ions is of dipole–dipole type. The results obtained after release of pressure reveal that there is a small hysteresis.     

Spectroscopic investigations of 1.06 μm emission in Nd-doped alkali niobium zinc tellurite glasses

Thermal, structural and optical properties of Nd³⁺ ions in tellurite glass (TeO₂-ZnO-Na₂O-Li₂O-Nb₂O₅) have been investigated. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section of the ⁴F_3/2→⁴I_9/2, _{11/2, 13/2} transitions. The quantum efficiency of the ⁴F_3/2 level is comparable as well as higher than the typical value of the other tellurite based glasses. The decay from the ⁴F_3/2 level is found to be single exponential for different concentrations of Nd³⁺ ions with a shortening of lifetime with increasing concentration. The experimental values of branching ratio and saturation intensity of ⁴F_3/2→⁴I_11/2 transition indicate the favourable lasing action with low threshold power.     

正偏离Bragg定律的二元化合物靶中离子射程参数研究

研究了正偏离Bragg定律,即计算S_e(E)值高于实测S_e(E)的二元系化合物靶的离子射程特性。文中应用“regular”观点引入了“双原子模型”,在二元化合物靶的射程计算中,不仅考虑相同“原子对”对离子的阻止本领S₁₁(E),S₂₂(E),而且考虑不同“原子对”对离子的阻止本领S₁₂(E),S₂₁(E)。文中还应用Berthelot关系,使S₁₂(E)=S₂₁(E)=(S₁₁(E)·S₂₂(E))^1/2,则二元系靶的阻止本领及总的射程为NS(E)=1/2[(N₁S₁₁(E))^1/2+(N₂S₂₂(E)^1/2)]², R=4/a[x-A₁(arctg(2x+f)/△^1/2-arctg(f/△^1/2))-B₁(ln(x+g)²/g²·e/(x²+fx+e)) -b/2 ln(x²+fx+e/e)。这里X=E^1/2,E为离子注入能量,所有其它常数是与离子和靶的质量、原子序数有关的常数。结合文献[1]提出的R与R_p,R_p与△R_p的关系式,可计算得正偏离系统的投影射程R_p及其偏差量△R_p。并对各关系式的物理意义作了阐明。 关键词：     

Infrared, visible and upconversion emission of CaAl12O19 powders doped with Er3+, Yb3+ and Mg2+ ions

CaAl₁₂O₁₉ powders doped with Er³⁺, Yb³⁺, and Mg²⁺ ions have been prepared by a low-temperature combustion synthesis technique. Formation and chemical compositions were analysed by powder X-ray diffraction and energy-dispersive spectroscopy. The visible luminescence spectra of the doped phosphor upon excitation with ∼378 nm radiation from a Xenon lamp have been studied. A broad band emission in the range of 1400–1700 nm with a peak around 1.5 μm and FWHM of about ∼80 nm responsible for the eye-safe telecommunication window has been observed upon direct excitation with a NIR laser into the ⁴I_11/2 level of Er³⁺. The effect of co-doping with Yb³⁺ and Mg²⁺ ions in the CaAl₁₂O₁₉:Er³⁺ matrix on the photoluminescence intensity corresponding to the ²H_11/2,⁴S_3/2→⁴I_15/2, ⁴F_9/2→⁴I_15/2 and ⁴I_13/2→⁴I_15/2 transitions of Er³⁺ is elaborated and discussed in detail.     

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.     

Er3+：GdVO4中Er3+离子的光谱参数计算和晶场中能级分裂的讨论

对Er³⁺：GdVO₄样品的光谱参数以及Er³⁺在晶场中能级的分裂情况进行了研究. 首先对样品进行了吸收光谱的测量，接着用Judd-Ofelt理论拟合出了Er³⁺在GdVO₄晶体中的强度参量Ω_t，并由此计算了跃迁的振子强度、自发辐射跃迁速率、荧光分支比和积分发射截面. 通过计算结果可以发现有较多能级之间的跃迁都有大于10^-6的振子强度和大于10^-18cm的积分发射截面，并且具有较高的荧光分支比，特别是²H_11/2→⁴I_15/2，⁴S_3/2→⁴I_15/2，⁴F_9/2→⁴I_15/2和⁴I_13/2→⁴I_15/2等几个强发光能级除了具有较大的振子强度和积分发射截面外还有很好的应用前景，因此也更加值得关注. 最后还利用群论讨论了Er³⁺离子在GdVO₄晶场中各能级的分裂情况并对各Stark子能级的J_z混杂情况进行了分析.     

Enhanced infrared to visible upconversion emission in Er3+ doped phosphate glass: Role of silver nanoparticles

Phosphate glasses with compositions (59.5–x)P₂O₅–MgO–xAgCl–0.5Er₂O₃ (0.0≤x≤1.5 mol%) containing fixed concentration of Er³⁺ ion with and without silver nanoparticles (NPs) are prepared using melt quenching technique. The amorphous nature of the glass is confirmed using the X-ray diffraction method. The homogeneous distribution of spherical Ag NPs (average size ～37 nm) in the glassy matrix is evidenced from the transmission electron microscopy (TEM) analyses. The UV–vis–NIR absorption spectra shows 10 bands corresponding to ⁴I_13/2, ⁴I_11/2, ⁴I_9/2, ⁴F_9/2, ⁴S_3/2, ²H_11/2, ⁴F_7/2, ⁴F_5/2, ²G_9/2, ⁴G_11/2 transitions in which the most intense bands are ²H_11/2 and ⁴G_11/2. The absorption spectrum of Er³⁺ ions free glass sample containing Ag NPs displays a prominent surface Plasmon resonance (SPR) band located at 528 nm. The infrared to visible frequency upconversion (UC) emission under 797 nm excitation shows two emission bands green (⁴S_3/2–⁴I_15/2) and red (⁴F_9/2–⁴I_15/2) centered at 540 nm and 634 nm, respectively, corresponding to Er³⁺ transitions. An enhancement in UC emission intensity of green band (⁴S_3/2–⁴I_15/2) is observed in the presence of silver NPs and the maximum enhancement occurred for 1.5 mol% AgCl. However, the enhancement of emission intensity of the red band (⁴F_9/2–⁴I_15/2) is smaller. The enhancement of UC emission is understood in terms of the intensified local field effect due to silver NPs.     

Excitation energy transfer between Er3+ and Tm3+ in LiNbO3

Conclusions Nonradiative energy transfer between similar and different rare-earth ions in LiNbO₃ has been evidenced for the first time. The contribution of nonradiative energy transfer to the decay of the¹G₄ and³H₄ levels of thulium and the⁴S_3/2 and⁴I_13/2 levels of erbium is significant for activator concentrations of the order of several thousand ppm in LiNbO₃. The excitation of higher-lying levels of both activators is transferred faster in codoped crystal to the lowest luminescent levels, from which the luminescence in the 1–2-μm spectral region occurs. This accelerated relaxation is advantageous for broadband optical pumping since the contribution of radiative transitions competing with the³F₄−³H₆ laser transition of thulium is reduced. On the other hand, it appears that erbium ions will influence adversely the efficiency of a laser-diode-pumped LiNbO₃∶Er, Tm laser operating near 1.8 μm since the part of the³H₄ excitation transferred to erbium ions is emitted from the long-lived⁴I_11/2 level of Er³⁺. Furthermore, the⁴I_13/2 excitation is not transferred fully to thulium ions and is lost in⁴I_13/2−⁴I_15/2 emission. Lithium niobate singly doped with thulium is more promising since the cross-relaxation process that transfers the excitation from the³H₄ level to the³F₄ level appears to be efficient in this host. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 5, pp. 125–133, September–October, 1995.     

尺寸效应对Er3+掺杂纳米Y2O3的发光特性的影响

采用燃烧法制备了不同尺寸的Er³⁺掺杂Y₂O₃粉体材料,研究了尺寸效应对Er³⁺掺杂纳米Y₂O₃材料发光特性的影响.光声光谱显示,对于不同晶粒尺寸的样品,Er³⁺离子光声峰位置几乎保持不变.这表明小尺寸效应对稀土离子能级位置影响很小.对488nm激光激发下的发射谱的分析发现,随着样品颗粒尺寸的减小,4S_3/2能级和关键词： 3+离子')" href="#">Er³⁺离子 纳米 发光 能量传递     

Structural and Upconversion Studies of Er3+ Codoped with CdS Nanoparticles in Sol-Gel Glasses

The Er³⁺ codoped with CdS nanoparticles in sol-gel glass with an average particle size of about 10 nm have been synthesized by sol-gel method. The green and red up-conversion emissions centered at about 534, 560 and 680 nm, corresponding to the ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺, respectively; were detected by a 800 nm excitation. The two-photon absorption process is involved in the green and red up-conversion emissions.