Low-temperature high-resolution VUV spectroscopy of Ce doped LiYF4, LiLuF4 and LuF3 crystals

For LiYF₄:Ce³⁺, LiLuF₄:Ce³⁺ and LuF₃:Ce³⁺ crystals UV/visible emission and time-resolved VUV/UV excitation spectra were recorded at liquid helium temperature with spectral resolution of 0.1 nm for excitation spectra and better than 0.3 nm for emission spectra. Well resolved fine structures due to zero-phonon lines were clearly observed in both excitation and emission spectra for LiYF₄:Ce³⁺ and LiLuF₄:Ce³⁺. For LuF₃:Ce³⁺ crystal no fine structure was detected in the spectra even at the highest spectral resolution. Under the host excitation, the fine structure for high-energy emission band of Ce³⁺ (5d-²F_5/2) in LiLuF₄:Ce³⁺ becomes well pronounced because of weaker reabsorption effect, as compared to Ce³⁺ 4f-5d absorption, due to small penetration depth for exciting radiation. As a result the crystal-field splitting for ²F_7/2 and ²F_5/2 levels of Ce³⁺ in LiLuF₄ crystal was measured. First observation of zero-phonon lines at ∼81,550 and ∼82,900 cm⁻¹ as well as vibronic side bands due to interconfigurational 4f¹⁴-4f¹³5d transitions in Lu³⁺ is reported for excitation spectrum of LiLuF₄:Ce³⁺.     

Improvement of thermal and spectroscopic behavior of Er<Superscript>3+</Superscript>/Ce<Superscript>3+</Superscript> co-doped tellurite glass for lasing materials

Tellurite glasses (TeO₂–ZnO–Nb₂O₅) mono-doped Er³⁺ and co-doped Er³⁺/Ce³⁺ have been prepared using the melt-quenching technique. To evaluate the effect of Ce³⁺ on the structural, thermal stability of glass hosts and fluorescence properties of Er³⁺, X-ray diffraction patterns, Ftir spectra, differential scanning calorimeter curves, absorption spectra, fluorescence emission spectra, fluorescence lifetimes, up-conversion emission spectra of glass samples were measured and investigated. Using Judd–Ofelt theory, we calculated intensity parameters (Ω₂, Ω₄ and Ω₆), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors and the quantum yield of luminescence for ⁴I_13/2 → ⁴I_15/2 transition. The co-doping with Ce³⁺ was effective on the suppression of up-conversion emission of Er³⁺ owing to the phonon-assisted energy transfer: Er³⁺:⁴I_11/2 + Ce³⁺:²F_5/2 → Er³⁺:⁴I_13/2 + Ce³⁺:²F_7/2 which contributed the effective enhancement of 1.53 µm fluorescence emission. The change in optical properties with the addition of Ce³⁺ ions have been discussed and compared with other glasses. Using the Mc Cumber method for the ⁴I_13/2 → ⁴I_15/2 transition, absorption cross-section, calculated emission cross-section, and gain cross-section values support that TZNEr1Ce1 glass is a potential material for developing broad-band and high-gain erbium-doped fiber amplifiers applied for 1.53 µm.     

Influence of γ-radiation on photoluminescence properties of YPO4:Eu3+,Ce3+ and YPO4:Dy3+,Ce3+ phosphors

Hexagonal YPO₄ phosphors doped with Eu³⁺/Dy³⁺ and co-doped with Ce³⁺ were synthesized by a hydrothermal route assisted using lauric acid as a capping agent. The prepared phosphors were characterized by transmission electron microscopy, infrared spectroscopy, powder X-ray diffraction and photoluminescence spectra. YPO₄: Eu³⁺ gives two red emission peaks at 587 and 610?nm corresponding to ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions, respectively. YPO₄: Dy³⁺ exhibits two emission peaks at 485?nm (blue) and 575?nm (yellow) corresponding to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions, respectively. Ce³⁺ ions enhanced the emission intensity as a co-dopant in both phosphors. Moreover, the effect of γ-radiation in the dose range 5–300?kGy on the photoluminescence behaviour of YPO₄:Eu³⁺,Ce³⁺ and YPO₄:Dy³⁺,Ce³⁺ was also investigated. Quenching of emission intensity, after irradiation at 5 and 300?kGy, was observed in both the phosphors due to loss of excess energy through a non-radiative relaxation process.     

Luminescence of La3F3[Si3O9]:Ce

The luminescence properties of Ce³⁺ in La₃F₃[Si₃O₉] are reported. Excitation and emission bands corresponding to 4f¹→5d¹ transitions of Ce³⁺ were identified. The center of gravity of the 5d states lies at remarkable high energy (43.2×10³ cm⁻¹) for Ce³⁺ in a silicate compound. This high value is attributed to the combined oxygen/fluoride coordination of the Ce³⁺ ion. Emission from the lowest 4f5d level to the ²F_5/2 and ²F_7/2 levels was found at 32.4×10³ and 30.4×10³ cm⁻¹. These results are compared with literature data on silicates and fluorides. From the values found for Ce³⁺, predictions are made for the positions of the 4f5d bands of Pr³⁺ and Er³⁺ in La₃F₃[Si₃O₉]. For both ions, it is concluded that in this host lattice emission is expected from high lying 4fⁿ energy levels.     

Intensity and bandwidth of multiphonon vibronic transitions of rare-earth ions in crystals

The theory of multiphonon vibronic coupling to electronic transitions is applied in analysing fluorescence spectra of Eu²⁺ in BaFCI, which consist of the 4f⁷(⁶P_7/2,) → 4f⁷(⁸S_7/2) and 4f⁶5d → 4f⁷ transitions, and the 4f⁷-4f⁶5d excitation spectrum of Ce³⁺ in YPO⁴. The 4f electrons are weakly coupled to lattice vibration modes so that only weak one- and two-phonon sidebands are observable in the 4f-4f optical transitions, whereas the electron-phonon coupling is significantly stronger for a 5d electron. Accordingly, intensive multiphonon vibronic transitions overwhelmingly dominate the 4f⁶5d → 4f⁷ spectrum. It is shown that the extended Judd-Ofelt theory for weak vibronic coupling in the framework of the M-process is equivalent to the Huang-Rhys theory for the δ-process. In the analysis of experimental data, contributions from local ligand modes and lattice acoustic modes are separated, and the coupling strength is evaluated, in terms of the Huang-Rhys parameter S, for the 4f-4f and 5d-4f vibronic transitions.     

Ce3+对Er3+/Yb3+共掺TeO2-WO3-ZnO玻璃发光性能的影响

在Er³⁺/Yb³⁺共掺TeO₂-WO₃-ZnO玻璃中引入Ce³⁺，研究了Ce³⁺对Er³⁺1.5μm发射性能及其上转换发光性能的影响。结果表明，随Ce³⁺浓度的增加Er³⁺1.5μm波段的荧光强度先增强后降低，优化的Ce³⁺掺杂浓度在2.07×10²⁰/cm³左右；1.5μm波段的荧光寿命则随Ce³⁺浓度的增加有轻微降低，从3.4ms降到3.0ms，但Ce³⁺浓度的增加对1.5μm波段的荧光半高宽基本无影响；Er³⁺/Ce³⁺间的交叉弛豫Er³⁺(⁴I_11/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_13/2)+Ce³⁺(²F_7/2)使玻璃的上转换发光强度大大降低，但在过高的Ce³⁺浓度下，Er³⁺/Ce³⁺间的另一交叉弛豫Er³⁺(⁴I_13/2)+Ce³⁺(²F_5/2)→Er³⁺(⁴I_15/2)+Ce³⁺(²F_7/2)则使Er³⁺⁴I_13/2能级粒子数减少，导致1.5μm波段荧光强度和荧光寿命降低. 关键词： 碲钨酸盐玻璃 发光性能 3+离子')" href="#">Er³⁺离子 3+离子')" href="#">Ce³⁺离子 交叉弛豫     

Vacuum ultraviolet spectroscopy of pure and Ce3+-doped Na0.4Lu0.6F2.2

The spectroscopic properties of wide-band fluoride Na_0.4Lu_0.6F_2.2 crystals activated by Ce³⁺ were investigated. The absorption edge for the matrix was found to be at about 9.5 eV. In the 4- to 8-eV region of the absorption spectrum of Na_0.4Lu_0.6F_2.2: Ce³⁺, all 4f-5d transitions of the Ce³⁺ ion are observed. In Na_0.4Lu_0.6F_2.2: Ce³⁺ crystals, ultraviolet/visible emission, reflection and time-resolved vacuum ultraviolet/ultraviolet excitation spectra were recorded at liquid helium and room temperatures.     

Formation of a stable bivalent state of Yb ions in Na4Y6F22:Ce3+, Yb3+ crystal under intense UV irradiation

The evolution dynamics of absorption spectra induced in samples of Na₄Y₆F₂₂:Ce³⁺, Yb³⁺ crystal by radiation resonant with 4f-5d transitions of Ce³⁺ ions was studied and analyzed. It was found that at least two types of color centers with different life times are induced in the studied crystal. It is established that the group of absorption bands in the UV spectral range that demonstrate long-term stability after excitation is caused by the 4f ¹³–4f ¹²5d transitions of bivalent ytterbium ions. The sequence of processes that lead to the reduction of ytterbium ions from the trivalent to the bivalent state is proposed.     

Dependence of the Er<Subscript>2</Subscript>O<Subscript>3</Subscript> selective emission on the intensity of laser thermal excitation

The dependence of the selective emission (SE) spectra of erbium oxide (Er₂O₃) in the visible and near-IR spectral ranges on the laser excitation intensity at a wavelength of 10.6 μ m is experimentally studied. The intensity ratio for the Er³⁺ electronic and vibronic transitions in the SE spectra is varied with an increase in the laser intensity to 10 kW/cm². The mechanism for the multiphonon fluctuation excitation of electronic states and a possibility for the SE application in the observation of the thermo-photo-laser effect are discussed.     

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.     

VUV 5<Emphasis Type="Italic">d</Emphasis>-4<Emphasis Type="Italic">f</Emphasis> luminescence of Gd<Superscript>3+</Superscript> and Lu<Superscript>3+</Superscript> ions in the CaF<Subscript>2</Subscript> host

The first observation and characterization of Lu³⁺ 4f ¹³5d-4f ¹⁴ luminescence from the CaF₂: Lu³⁺ crystal are reported, and the multisite structure in the spectra of Ce³⁺, Gd³⁺, and Lu³⁺ ions in the CaF₂ host is analyzed with the high-resolution VUV spectroscopy technique using synchrotron radiation. It is shown that vibronic structure in the emission and excitation spectra of interconfigurational transitions in Gd³⁺ and Lu³⁺ ions doped into CaF₂ differs from that observed for Ce³⁺ ions entering mainly at the tetragonal (C _4v ) sites. However, the exact types of sites in which the Gd³⁺ and Lu³⁺ ions reside in a CaF₂ lattice cannot be identified using only the obtained experimental spectroscopid data. The text was submitted by the authors in English.     

UV and VUV spectroscopic study of Na0.4Y0.6F2.2 crystals doped with rare-earth ions

The short-wavelength transmission spectra of Na_0.4 R _0.6F_2.2 crystals with R = Y, Yb, or Lu have been investigated. For these crystals, the VUV transmission cutoffs are 78750, 58820, and 75200 cm^?1, respectively. The 4f ⁿ–4f ^n?15d absorption and excitation spectra of Na_0.4Y_0.6F_2.2 crystals activated with Ce³⁺, Pr³⁺, Nd³⁺, Er³⁺, Tm³⁺, and Yb³⁺ ions have been analyzed in the range 30000–80000 cm^?1. The energy positions of the lowest levels of the 4f ^n?15d configurations of these ions in the fluorite crystal matrix Na_0.4Y_0.6F_2.2 are determined. The absorption band in the spectral range 60600–70000 cm^?1 in Na_0.4(Y, Yb)_0.6F_2.2 crystals is due to the charge transfer from F^? to Yb³⁺. It is shown that the environmental symmetry of Ce³⁺ ions in Na_0.4R_0.6F_2.2 (R = Y, Yb, Lu) crystals is almost identical.     

Ce3+对Er3+/Yb3+共掺氟磷酸盐玻璃光谱性质的影响

研究了能量接受离子Ce³⁺对Er³⁺上转换发光强度以及Er³⁺在1.5μm附近波段发光性能参数的影响，并从能量匹配及能级结构角度出发对Er³⁺/Ce³⁺间的能量转移机制进行了分析.分析认为，⁴I_11/2能级的Er³⁺通过无辐射能量转移把能量传递给²F_5/2能级的Ce³⁺关键词： 氟磷酸盐玻璃 光谱性质 光纤放大器 3+和Ce³⁺')" href="#">Er³⁺和Ce³⁺     

Visible luminescence of nanocrystalline AlN:Er thin film by co-deposition of AlN,Er, and SiO2

We report a visible luminescence of Er³⁺ ions in an amorphous-nanocrystalline AlN:Er thin film prepared by co-deposition using AlN, Er, and SiO₂ targets. A PL emission spectrum of Er³⁺ in the AlN:Er film annealed at 750 °C showed a strong bluish green emission of Er³⁺ in the amorphous-nanocrystalline AlN:Er thin film, which is attributed to the intra-4fEr³⁺ transitions of ²H_11/2 → ⁴I_15/2 and ⁴F_7/2 → ⁴I_15/2. It was found that crystallite diameters were between 3 and 5 nm by high-resolution transmission electron microscopy. The occurrence of the strong Er³⁺ emission in the annealed AlN:Er thin film with a mixture of amorphous and nanocrystalline phases may be contributed to an increase in the number of excitation Er³⁺ centers and a presence of oxygen related to Er³⁺ excitation and recombination process in the AlN:Er thin film.     

Spectra of optical absorption and energy levels diagram of Er<Superscript>3+</Superscript> ions in bulk crystals of aluminum nitride

The absorption spectra of the Er³⁺ ions embedded in the AlN matrix have been investigated. The admixture of erbium was introduced in bulk AlN crystals by diffusion. The absorption lines, which are associated with the intraconfigurational electronic f–f-transitions from the ground ⁴ I _15/2-state to the levels of ion Er³⁺ excited states have been observed in the spectral range of 370–700 nm. The transitions to the state levels ⁴ F _9/2, ² H _11/2, ⁴ F _7/2, ⁴ F _5/2, ² H _9/2, and ⁴ G _11/2 have been investigated in detail at the temperature T = 2 K. The number of the observed lines for these transitions coincides with the theoretically possible one for the electronic f–f-transitions in the ions Er³⁺, which are in the crystal field with the symmetry below cubic. The narrowness of the observed lines and their number convincingly testify the replacement of preferably one regular crystalline position by erbium ions. The implementation of Er³⁺ in the Al³⁺ position with the local symmetry C _3v appears the most probable. The energy positions of the levels of excited states for the investigated transitions have been determined. The diagram of the Er³⁺ ion energy levels in the AlN crystals has been built.     

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.     

luminescence of BaGa<Subscript>2</Subscript>Se<Subscript>4</Subscript> crystals activated by Eu<Superscript>2+</Superscript> and Ce<Superscript>3+</Superscript> ions

We have studied the effect of doping with Eu²⁺ and Ce³⁺ ions on the photoluminescence (PL) of BaGa₂Se₄ crystals in the temperature range 77–300 K. We have established that the broad bands with maxima at wavelengths 456 nm and 506 nm observed in the photoluminescence spectra of BaGa₂Se₄:Ce³⁺ crystals are due to intracenter transitions 5d → ²F_7/2 and 5d →²F_5/2 of the Ce³⁺ ions, while the broad photoluminescence band with maximum at 521 nm in the spectrum of BaGa₂Se₄:Eu²⁺ is associated with 4f⁶ 5d → 4f⁷ (⁸S_7/2) transitions of the Eu²⁺ ion. We show that in BaGa₂Se₄:Eu²⁺,Ce³⁺ crystals, excitation energy is transferred from the Ce³⁺ ions to the Eu²⁺ ions.     

Yb3+敏化的Er3+/Ho3+共掺碲酸盐玻璃的上转换发光研究

用高温熔融法制备了系列Er³⁺/Yb³⁺共掺，Ho³⁺/Yb³⁺共掺，和Er³⁺/Yb³⁺/Ho³⁺三掺碲酸盐玻璃，在975nm激光抽运下三种掺杂玻璃中都出现了较强的绿光和红光上转换.研究了Yb³⁺离子对Er³⁺和Ho³⁺离子上转换发光强度的影响以及Yb³⁺→Er关键词： 3+/Yb³⁺/Ho³⁺共掺')" href="#">Er³⁺/Yb³⁺/Ho³⁺共掺 碲酸盐玻璃 光谱性质 上转换     

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：     

VUV spectroscopy of Ce<Superscript>3+</Superscript>-doped Na<Subscript>0.4</Subscript>Lu<Subscript>0.6</Subscript>F<Subscript>2.2</Subscript> single crystals

The short-wave transmission spectrum of Na_0.4Lu_0.6F_2.2 with the visible/ultraviolet transmission edge of 8 eV was studied. Absorption spectra of the 4f—5d transitions of the Ce³⁺ ion in the region of 4–8 eV were studied in Ce³⁺-doped Na_0.4Lu_0.6F_2.2 single crystals. Luminescence spectra in the ultraviolet and visible spectral regions, luminescence decay kinetics and reflection and luminescence excitation spectra in the visible/ultraviolet and ultraviolet regions (4–20 eV) were investigated at helium and room temperatures.