[en] A series of new glasses of 70TeO₂-(20-x) ZnO-xWO₃-5La₂O₃-2.5K₂O-2.5Na₂O (mol %) doped with Yb³⁺ is presented. Thermal stability and spectroscopic properties of Yb³⁺ ions have been measured. It found that 70TeO₂-15WO₃-5ZnO-5La₂O₃-2.5K₂O-2.5Na₂O composition glass had better thermal stability ((T_x-T_g)>160 deg. C) than 75TeO₂-20ZnO-5Na₂O glass, high-stimulated emission cross-section of 1.32 pm² for the ²F_5/2→²F_7/2 transition and existed measured fluorescence lifetime of 0.93 ms and the broad fluorescence effective linewidth of 74.5 nm. Evaluated from the good potential laser parameters, this system glass is promising for miniature solid fiber lasers or high-peak power and high-average power lasers, also for wave-guides or tunable lasers

[en] The absorption, emission and potential laser properties of silicate glasses doped with Yb³⁺ ions are investigated in detail. The emission cross-sections (σ_emi) are calculated on the basis of reciprocity method according to the measured absorption spectra. The potential laser properties for Yb³⁺-doped glasses are evaluated by the minimum fraction of Yb³⁺ (β_min), the pump saturation intensity (I_sat), the minimum pump intensity (I_min), and the product of emission cross-section (σ_emi) and fluorescence lifetime (τ_f). The σ_emi near 1020 nm and τ_f of Yb³⁺ in 61SiO₂-25PbO-6Na₂O-8K₂O glass are 0.49 pm² and 2.00 ms, respectively, which are comparable to those in phosphate glasses. Systematical factor of laser properties (SFL) is introduced to evaluate the potential laser properties of Yb³⁺-doped glasses, the results indicate that Yb³⁺-doped silicate glasses are potential materials for double cladding ytterbium fiber laser application

[en] Er³⁺-doped heavy metal oxyfluoride germanate glass suitable for developing potential optical amplifiers and upconversion lasers has been fabricated and characterized. Under 975 nm excitation, intense and broad 1533 nm infrared fluorescence and visible upconversion fluorescence were observed. For 1533 nm emission band, the full width at half maximum (FWHM) is 57 nm, the fluorescence lifetime is 5.7 ms, and the quantum efficiency is ∼100%. Efficient 529, 551, and 657 nm upconversion emissions correspond to the transitions ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2, respectively. Raman spectrum indicates the important role of fluoride ions in the formation of glass network. The dependence of upconversion intensities on excitation power involves two-photon absorption processes for the three emission bands. The possible upconversion mechanisms are discussed based on the energy matching conditions and the quadratic dependence on excitation power

[en] The effect of radiative trapping on measurement of the spectroscopic properties of Yb³⁺-doped phosphate glasses was investigated as a function of Yb³⁺ concentration at different thicknesses. It was found that radiative trapping exists generally in Yb³⁺:phosphate glasses, even at low concentration. As a result, the measured lifetime of Yb³⁺ in phosphate glasses is usually larger than the calculated one. The maximum discrepancies between them at high concentration are found to be <42%. The calculated lifetime should be used as a reference in determining the true value of the measured lifetime because of it being lengthened largely by radiative trapping. On the other hand, the shape of fluorescence spectrum exhibits remarkable changes due to the radiative trapping. What is more, the intensity increase of Δλ_eff at high concentration is greater than that of low doping. The Δλ_eff increases 36% from 53 to 72 nm with thickness increasing from 0.3 to 4 mm at 6 mol% Yb₂O₃ content, while Δλ_eff increases only 11% when Yb₂O₃ content was fixed at 0.2 mol%

[en] The green and red upconversion luminescence of Er³⁺ in lead chloride tellurite glasses excited at 980 nm is investigated. Three intense emission bands centered at 530, 545, and 658 nm corresponding to the transitions ⁴S_3/2→⁴I_15/2, ²H_11/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2, respectively, were simultaneously observed at room temperature. With increasing PbCl₂ content, the intensity of green (530 nm) emissions increase slightly, while the green (545 nm) and red (658 nm) emissions increase significantly. The results indicate that PbCl₂ has more influence on the green (545 nm) and red (658 nm) emissions than the green (530 nm) emission. The dependence of upconversion intensities on excitation power and possible upconversion mechanisms are discussed and evaluated

[en] The upconversion properties and mechanism of Er³⁺ ions have been studied for lead oxyfluorosilicate glasses containing Er₂O₃ concentrations from 0.2 to 2 mol%. Under 975 nm excitation, four emission bands centered at 411, 525, 543, and 655 nm corresponding to the ²H_9/2→⁴I_15/2, ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺ ions, respectively, were simultaneously observed at room temperature. The bright green and red emissions are due to a two-photon upconversion process while the weak blue emission is determined by a three-photon upconversion process. Raman spectrum indicates that fluoride ions in the formation of glass network have important influence on upconversion luminescence of Er³⁺ in lead oxyfluorosilicate glasses. The intense upconversion luminescence of Er³⁺-doped lead oxyfluorosilicate glasses may be a potentially useful material for developing upconversion optical devices

[en] A series of new glasses of 70TeO₂-(20-x) ZnO-xGeO₂-5La₂O₃-2.5K₂O-2.5Na₂O (mol%) doped with Yb³⁺ is presented. Thermal analysis, spectra and laser properties of Yb³⁺ ions have been measured. It is found that 70TeO₂-20GeO₂-5La₂O₃-2.5K₂O-2.5Na₂O composition glass had better thermal stability than 75TeO₂-20ZnO-5Na₂O glass, higher stimulated emission cross-section of 1.23 pm² for the ²F_5/2→²F_7/2 transition close to PN glass, lower minimum pump intensity of 0.98 KW/cm², long fluorescence lifetime of 0.92 ms and the broad fluorescence effective line width of 77 nm. Evaluated from the good potential laser parameters, this system glass is a promising host of miniature solid lasers such as short pulse generation in diode pumped lasers, short pulse generation tunable lasers, high-peak power and high-average power lasers, etc

[en] Highlights: • ZnSb-doping can effectively enhance thermal stability of Sb_2Te_3 films. • Sb-rich changes crystal phase but their grain size is refined with Zn addition. • The Sb-rich increases the speed while maintaining enhancing crystallization temperature. • High Sb/Te ratio reveals the improvement in cycle ability. - Abstract: Crystallization process and amorphous state stability of pseudobinary ZnSb-Sb_2Te_3 materials have been studied for application in phase change memory. The effects of Zn concentration and Sb content on crystalline resistance, crystallization temperature, crystallization activation energy and amorphous state stability of films have been studied. The microstructures of Sb-rich Zn-Sb-Te films were analyzed through X-ray diffraction. Different crystalline phases have been observed in annealed Sb-rich Zn-Sb-Te films. Low Zn-doping concentration Zn-Sb-Te films crystallized into rhombohedral Sb_2Te_3 phase while high Zn-doping concentration Zn-Sb-Te films crystallized into rhombohedral Sb phase. The crystallization activation energy (E_a) of Zn_1_._1Sb_4_5_._7Te_5_3_._2 and Zn_5_._2Sb_4_6_._3Te_4_8_._5 films were confirmed to be 2.0 and 2.93 eV, while E_a of Zn_1_6_._0Sb_4_7_._3Te_3_6_._7 film increased to 3.2 eV and further reached to 3.3 eV for Zn_1_9_._7Sb_4_8_._1Te_3_2_._2 film. Zn addition increased the crystallization temperature and crystalline resistance of Zn-Sb-Te films largely, and enhanced the amorphous thermal stability and data retention ability of the films, while high Sb/Te ratio reveals the improvement in crystallization speed and good cycle ability. Therefore, Sb-rich Zn-Sb-Te film seems to be a good way to solve the contradiction between thermal stability and fast crystallization speed

[en] Nonradiative decay of ⁴I_13/2→⁴I_15/2 transition of Er³⁺ has been investigated in a series of oxide glasses. For Er³⁺-doped glass samples, the Judd-Ofelt analysis on absorption spectra was performed and the fluorescence lifetime was determined by extrapolating to zero Er³⁺ concentration limit. Infrared spectra were measured in order to investigate the influence of OH^- groups in different glasses. The effects of glass matrix on the decay rate were discussed from the viewpoint of phonon energy, variations of effective fields, and OH^- groups. Compared to other glasses, phosphate glass presents low quantum efficiency and large nonradiative decay rate due to its high phonon energy and hygroscopic behavior

[en] The Zn-doped Sb_2Te_3 films have been investigated systematically during the phase transformation process. It was found that, the increase of crystallization temperature in the Zn-doped Sb_2Te_3 films leads to its enhanced amorphous stability, and Zn incorporation can increase electrical resistance, widen optical band gap and refine crystalline grain size. The crystallization mechanism can be tuned into nucleation-dominated from growth-dominated type. Moreover, Sb_2Te_3 film with high Zn-doping concentration such as Zn_3_8_._8(Sb_2Te_3)_6_1_._2 film was found to exhibit a higher crystallization temperature (233 °C), better data retention ability (keeping the amorphous state at 146.5 °C for ten years), and wider band gap (0.839 eV). A lower threshold of crystallization (~ 25 ns) can be realized in the Zn_3_8_._8(Sb_2Te_3)_6_1_._2 film irradiated at the laser power of 70 mW in comparison with that in the conventional Ge_2Sb_2Te_5 film. We confirm that the Zn doping is responsible for a fast switching and the Zn_3_8_._8(Sb_2Te_3)_6_1_._2 compound is stable against segregation with cycling. - Highlights: • Zn-doping can effectively enhance thermal stability of Sb_2Te_3 films. • Zn-doping can effectively refine their grain size. • A short crystallization time (~ 25 ns) can be realized in the Zn_3_8_._8(Sb_2Te_3)_6_1_._2 film. • A reversible phase change process can be realized in Zn_3_8_._8(Sb_2Te_3)_6_1_._2 film