Jinhao Wang

Gain properties of germanate glasses singly doped with Tm3+ and Ho3+ ions

Two kinds of germanate glasses singly doped with the ion concentration of 2.0mol.%Tm3+ and 2.0mol.%Ho3+, respectively, were prepared. According to McCumber theory, the absorption and stimulated emission cross-sections corresponding to the 3H6↔3F4 transitions of Tm3+ (at 1.8 µm) and the 5I8↔5I7 transitions of Ho3+ (at 2.0 µm) were obtained, and respective gain cross-section spectra were also computed as a function of population inversion according to absorption and emission cross-sections and the ion concentrations. For Tm3+-doped germanate glasses, the maximum of the absorption, emission, and gain cross-sections reached a value higher than those reported for fluorozirconate, fluoride, and oxyfluoride glasses. For Ho3+-doped germanate glasses, the maximum of absorption, emission, and gain cross-sections reached a value higher than that reported for fluorozircoaluminate glasses. Hence, these Tm3+-doped and Ho3+-doped germanate glasses exhibited an advantage for application in mid-infrared lasers at about 1.8 and 2.0 µm wavelength.

Cooperative energy transfer in Tm3+ and Yb3+ co-doped phosphate glasses

Abstract An efficient near-infrared (NIR) quantum cutting (QC) in Tm 3+ and Yb 3+ co-doped phosphate glasses was demonstrated, which involved the emission of two NIR photons from an absorbed visible photon via a cooperative energy transfer (CET) from Tm 3+ to Yb 3+ ions. Judd-Ofelt (J-O) theory was used to calculate the intensity parameters (Ω 2 , Ω 4 , Ω 6 ), the radiative transition rates ( A r ), and radiative transition lifetime (τ rad ) of Tm 3+ . Based on Inokuti-Hirayamas model, the energy transfer processes were studied and results indicated that the energy transfer of the electric dipole-dipole (Edd) was dominant in this system. Quantum efficiency related to Yb 3+ concentration was calculated, and the maximum QE efficiency reached 169.8%.

Optical Spectroscopy of Er3+ and Er3+/Yb3+ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

Abstract The (60 - x )Bi 2 O 3 - x GeO 2 -30B 2 O 3 -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 GeO 2 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 Ω 2 , Ω 4 , and Ω 6 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+ .

Optical spectroscopy and crystal-field strength of Cr3+ in various solid matrixes

Abstract The Cr 3+ :BeAl 2 O 4 crystal, Cr 3 :LiNbO 3 crystal, and ZnO-Al 2 O 3 -SiO 2 glass-ceramic were obtained by the Czochralski technique, Bridgman method, and melting processing, respectively. The optical absorption and emission spectra of the above Cr 3 -incorporated solid-state materials were recorded. The technical parameters for growing high-quality Cr 3+ :BeAl 2 O 4 and Cr 3+ :LINbO 3 crystals were obtained. The results indicate that the optical absorption and fluorescence spectra of Cr 3+ show quite a few differences in various matrixes. The sharp line emissions were observed in the Cr 3+ :BeAl 2 O 4 and Cr 3+ :LiNbO 3 crystals. The crystal-field parameters ( D q ) for Cr 3+ in different matrixes were calculated from their corresponding spectra. It is indicated that Cr 3+ :BeAl 2 O 4 and Cr 3+ :LiNbO 3 belong to the high-field site crystal, while the Cr 3+ :ZnO-Al 2 O 3 -SiO 2 glass and glass-ceramic belong to the weak-field site crystal.

Growth and Optical Spectra of Zn:Er:LiNbO3 Crystals Using Bridgman Method

Abstract The growth of LiNbO 3 single crystal with Er 3+ and Zn 2+ co-doped using Bridgman method and its characteristic absorption spectra and fluorescence spectra were reported. Large-size crystals initially containing Zn 2+ (3%) and Er 3+ (0.6%) with good optical quality were obtained using optimized conditions such as a growth rate of 0.8 ∼ 1.5 mm·h −1 and a temperature gradient of about 30 ∼ 35 °C · cm −1 across the solid-liquid interface and the sealed platinum crucible. X-ray diffraction and differential thermal analysis (DTA) were used to characterize the crystals. The results indicate that the concentration of Er 3+ ions in crystals, their absorption intensity, and their fluorescence intensity decrease from the bottom to the top in the crystals. However, for the upper part of the crystal, the up-conversion fluorescence intensity is higher than that of the lower part excited by an 800 or 970 nm pump. The effects of the crystal lattice, their structural defect and their effective segregation of Er 3+ ions were discussed with respect to the variations of the up-conversion fluorescence intensity.

Preparation and optical spectroscopy of Na2O–TeO2–ZnO glasses containing divalent europium ions

Abstract Eu 2 O 3 was incorporated into Na 2 O–TeO 2 –ZnO glasses by a melting method in air atmosphere. The fluorescence, excitation spectra of the glasses, was studied. The results indicate that some of the europium ions in the glass exist in state of divalent although they were prepared at air atmosphere. The IR spectra of the glasses were measured. The structural and compositional effects on the state of europium ions were discussed.

Microstructure and magnetostrictive properties of epoxy-bonded Tb1-xNdx(Fe0.8Co0.2)1.93 (0.20 ≤ x ≤ 0.75) composites

An epoxy-resin bonding route was used to produce composite rods of the highly magnetostrictive alloys Tb1-xNdx(Fe0.8Co0.2)1.93 (0.20 ≤ x ≤ 0.75). The structure, spin configuration, magnetostriction and particle size are investigated by means of X-ray diffraction (XRD), a standard strain technique and scanning electron microscope (SEM). The epoxy-bonded 0–3 type and pseudo 1–3 type composites are successfully fabricated, respectively. XRD analysis shows that the easy magnetization direction (EMD) for the alloy of x = 0.20 lies along 〈111〉 axis. The magnetic curing field makes the particles align as a particulate chain and also causes the particles rotating along its EMD direction. The pseudo 1–3 type epoxy-bonded composite has a larger magnetostriction than that of the 0–3 type composite, which can be attributed to the larger magnetostriction coefficient λ111, EMD lying along 〈111〉 direction, the 〈111〉-textured orientation and the chain structure. A large saturation magnetostriction (λ0S ~ 570 ppm) is achieved for the 1–3 type epoxy/Tb0.35Nd0.65(Fe0.8Co0.2)1.93 composite (about 150–250 μm, 10 kOe), which approaches 70% of its monolithic alloy. Furthermore, it only contains 27 vol.% alloy particles in the insulating epoxy matrix and performs a low magnetic anisotropy, which could make it technologically interesting for the field of Nd-containing magnetostrictive materials.

SPECTROSCOPIC PROPERTIES OF Ce3+-DOPED OXIDE GLASSES WITH HIGH Gd2O3 CONCENTRATIONS

Ce3+-doped oxide glasses containing high Gd2 O3 concentration are prepared and their transmission, emission and excitation spectra are measured. Dependence of spectroscopic properties on concentrations of Ce2 O3 and Gd2O3 are analyzed. The results show that the UV cut-off wavelength and the emission peaks show red shift, and Stokes shift increases with Ce2O3 and Gd2O3 concentrations due to the increasing optical basicity of the glasses. The emission intensity decreases with increased Ce2O3 and Gd2 O3 concentrations and showing the concentration quenching effect. The red shift of excitation peak is less when the Gd2O3 concentration increases, indicating that the energy transfer from Gd3+ to Ce3+ takes place in the oxide glasses with high Gd2O3 concentrations, and thus Gd3+ ions sensitize the luminescence of Ce3+ ions. The Ce3+ doped oxide glasses with high Gd2O3 concentrations will be a promising scintillator for applications in the high-energy physics and other fields.

OPTICAL CHARACTERIZATION OF Tb3+-DOPED Gd2O3 BASED SCINTILLATING GLASSES

We prepared Tb3+-doped Gd2O3-based oxide glasses by high-temperature melting method and presented their density and optical characterization including transmission, emission and excitation spectra. Dependence of density and luminescence properties on the concentration of Tb3+ and Gd2O3 was also analyzed. The results show that rising Tb3+ ions concentrations would lead to the reduction of distance between Tb3+ ions, the increase of probabilities of energy resonate-transfer and a stronger luminous intensity. In addition, a high Gd2O3 concentration was beneficial to improve the glass samples density, but exerting a negative effect on Tb3+ ions and decreasing the luminous intensity of Tb3+ ions.

PREPARATION AND SPECTROSCOPIC PROPERTIES OF Yb:YAG GLASS-CERAMICS

Yb3+-doped 32CaO-12Y2O3-24Al2O3-31SiO2-1Yb2O3 glasses were prepared by melting method, and then annealed at 950°C, 1050°C and 1100°C, respectively. We analyzed the crystallographic structures of the glasses annealed at different temperatures by XRD, and observed the glass annealed at 1050°C by TEM. The spectroscopic properties of glass before and after annealing were also investigated. Results show that the glasses annealed at 1050°C are YAG glass-ceramics with no impurity crystalline phase. Variances in the spectroscopic properties before and after heat treatment indicate that Yb3+ ions were preferentially partitioned into the YAG crystal phase, and the transparent Yb:YAG glass-ceramics were obtained.