Synthesis of well oil-dispersible BaYF5:Yb3+/Er3+ nanocrystals with green upconversion fluorescence

Nearly monodisperse, regular-shaped and well oil-dispersible tetragonal BaYF₅:0.2Yb³⁺/0.02Er³⁺ nanocrystals (NCs) were synthesized in water-ethanol-oleic acid-sodium oleate system. The as-obtained NCs exhibited bright upconversion (UC) fluorescence under the 980 nm excitation. Blue (²H_9/2-⁴I_15/2), green ((²H_11/2, ⁴S_3/2)-⁴I_15/2) and red (⁴F_9/2-⁴I_15/2) transitions were observed. The results indicated that the relative intensity of green to red increased gradually with increasing power density, which were seldom in the previous work. Therefore, the UC properties and mechanism were studied in detail.     

Upconversion of Er3+ Ions in LiKGdF5∶Er3+, Dy3+ Single Crystal Produced by Infrared and Green Laser

The upconversion fluorescence of Er3 ions in LiKGdF5∶Er3 , Dy3 single crystal was studied under 785, 514.5, and 980 nm laser excitation. With the laser excitation set at 785 nm, strong green (centered at 543 nm) upconversion emissions, as well as weak red (651 nm), violet (406 nm), and blue (470 nm) upconversion emissions were obtained. With 514.5 nm laser excitation, violet (406 nm) and blue (470 nm) upconversion emissions were observed. Under 980 nm laser excitation, strong green (543 nm) and weak red (651) emissions were also obtained. The laser power dependence of the upconverted emissions was investigated to understand the upconversion mechanism. The excited state absorption (ESA) and the energy transfer (ET) processes were discussed as the possible mechanisms for all upconversion emissions.     

Up-Conversion Emission of Er3+ Ions in Yb3+ Sensitized Oxide Crystals

Most of the up-conversion lasers operated at room temperature are realized with heavy metal fluorides, In this paper the Judd-Ofelt parameters Ωλ ( λ = 2,4,6 ) were calculated for Er3+ ions in Yb3 + sensitized LiNbO3 and YVO4 crystals at room temperature, together with the radiative transition probabilities, non-radiative transition probabilities and resonant transition probabilities of Er3+ ions. Taking into account the energy transfer from Yb3 + to Er3 +, the rate equations are given for Er3 + ions. We obtained from a solution of the rate equations that Yb3 + sensitized YVO4 crystal is more efficient than Yb3 + sensitized LiNbO3 crystal in the up-conversion of 550 nm of Er3+ emission, which is consistent with our observation.     

Polarized spectral analysis of Er3+ ions in Er3+/yb3+:LiLa(MoO4)2 crystal

Optical characteristics and upconversion dynamics of Er3+ in Er3+/Yb3+:LiLa(MoO4)2 crystals were investigated. The absorption spectra, fluorescence spectra and the fluorescence decay curves were analyzed at room temperature. The infrared emission at 1538 nm and visible emissions at 520–569 and 640–670 nm, corresponding to 2H11/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, were simultaneously observed in Er3+/Yb3+:LiLa(MoO4)2 crystals under 976 nm excitation at room temperature. The maximal emission cross-section near 1530 nm for π-polarization was 0.63×10–20 cm2 and the measured lifetime of 4I13/2 was 4.88 ms. The upconversion process was involved in sequential two-phonon processes, either the energy transfer from Yb3+ ions or by the excited state absorption.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Photon Cascade Emission through Energy Transfer in Pr^3＋and Er^3＋Codoped System

Energy transfer processes in Pr^3 -codoped CaAl12O19crystal from 12 to 290K were studied.Energy transfer from Pr^3 toEr^3 ions in this system was observed,The transfer can partially convert the ^1S0UVfluorescence of Pr^3 into green emission of the characteristic of Er^3 ,The efficiency of the energy transfer was estimated based of the spectroscopic data,The temperature dependence on the transfer was also discussed.     

Investigation on energy transfer from Er3+ to Nd3+ in teilurite glass

A study of energy transfer of Er3+/Nd3+ codoped tellurite glasses was presented. By Nd3+ co-doping, both the Er3+ green emission corresponding to the Er3+: (4S3/2,2H11/2)→4I15/2 transitions and the red emission corresponding to the Er3+: 4F9/2→4I15/2 transitions were quenched. The energy transfer mechanism between Er3+ and Nd3+ was discussed based on their energy level characteristics. The interaction parameters, CD-A, for the energy transfer processes from Er3+ to Nd3+ in tellurites glass were calculated. Finally, the resonant transfer Er3+: 4I9/2→Nd3+: (4F5/2, 2H9/2) was proposed to be the most probable microscopic process to occur in contrast with the other processes.     

Spectroscopic properties of Er3+-doped fluoroindate glasses

The optical and thermal properties of a new class of fluoroindate glass with different erbium contents were investigated via Raman, transmission, and fluorescence spectroscopies, fluorescence decay curve analysis, and differential scanning calorimetry. The strength parameters of the samples were calculated using the Judd–Ofelt theory. The mid-infrared luminescence properties of erbium-doped fluoroindate glasses were studied, and a strong emission at 2.7 μm was obtained. Compared with the traditional ZBLAN glass, this glass has excellent emission properties, especially a longer fluorescence lifetime (7.09 ms) and larger emission cross-section (6.95 × 10^?21 cm²) at 2.7 μm. The results indicate that fluoroindate glass is an attractive host for mid-infrared lasers and as a gain medium for optical amplifier applications.     

Upconversion Emission in Er^3＋ Doped Novel Bismuthate Glass

Novel Er3 -doped bismuth lead strontiam glass was fabricated and characterized, and the absorption spectrum and upconversion spectrum of the glass were studied. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were found to be Ω2＝3.27×10-20 cm2, Ω4＝1.15×10-20 cm2, and Ω6＝0.38×10-20 cm2. The oscillator strength, the spontaneous transition probabilities, the fluorescence branching ratios, and excited state lifetimes were also measured and calculated. The upconversion emission intensity varies with the power of infrared excitation intensity. A plot of log Iup vs log IIR yields a straight line with slope 1.86, 1.88 and 1.85, corresponding to 525, 546, and 657 nm emission bands, respectively, which indicates that a two-photon process for the red and green emission.