Upconversion luminescence of Tm^3＋/Yb^3＋ codoped oxyfluoride glasses

Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - （4.9 - x） AlF3（x=0, 0.5, 1.0, 1.5, 2.0） in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3＋： ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3＋ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3＋ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions.

Gain properties of germanate glasses singly doped with Tm^(3+) and Ho^(3+) 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.

Up-conversion photoluminescence characteristics of Yb^(3+):Er^(3+):Tm^(3+) co-doped borosilicate glasses

Yb^3＋：Er^3＋：Tm^3＋co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb^3＋ Er^3＋ and Tm^3＋ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb^3＋ Stark splitting levels to pump Tm^3＋ ions and there exists an optimum pump power. The concentration of the Tm^3＋ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the yb^3＋：Er^3＋：Tm^3＋ co-doped borosilicate glasses.

Tm^(3+)-doped tellurite glass with Yb^(3+) energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3＋ and Yb^3＋ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3＋ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3＋/Yb^3＋ co-doped tellurite glass as amplifier material were concluded.

Enhanced 1.8 μm emission in Er^(3+)/Tm^(3+) co-doped lead silicate glasses under different excitations for near infrared laser

A detailed study of the fluorescence emission properties and energy transfer mechanism in Er^（3＋）/Tm^（3＋） co-doped lead silicate glasses was reported. Enhanced near infrared 1.8 μm and visible up-conversion emissions were investigated under 808 and 980 nm excitations, respectively. The energy transfer mechanism between Er^（3＋） and Tm^（3＋） was analyzed according to the absorption spectra, the emission spectra and the level structures of Er^（3＋） and Tm^（3＋）. The energy transfer efficiency between Er^（3＋） and Tm^（3＋） reached 68.1% in the Er^（3＋）/Tm^（3＋） co-doped lead silicate glasses when pumped by 808 nm laser diode. Based on the absorption spectra, the Judd-Ofelt parameters, spontaneous emission probability, absorption and emission cross sections, gain coefficients were calculated and analyzed. It was found that the calculated emission cross section and the maximum gain coefficient around 1.8 μm were 4.9×10^（–21）cm^2 and 1.12 cm^（–1）, respectively. These results indicated that the Er^（3＋）/Tm^（3＋） co-doped lead-silicate glasses had potential application in near infrared lasers.

Temperature sensing behavior of Tm^3+:1G4(a),1G4(b) in oxyfluoride glass ceramics containing BaYbxY1-xF5 nanocrystals

Tm3+-doped transparent oxyfluoride glass ceramics containing BaYbxY((1-x))F5 nanocrystals were prepared via high temperature solid phase melting method,of which up-conversion emission is achieved by the Yb3+-mediated energy transfer process.The required photon number of Tm3+ions emissions in BaYbxY(1-x)F5 nanocrystals was calculated through the luminescence spectra,revealing the strong dependence of energy transfer mechanism on Yb3+ions concentration.Meanwhile,based on the fluore scence intensity ratio technology,the effect of different energy transfer mechanism on the temperature sensitivity was investigated by the temperature-dependent luminescence intensity of thermally coupled energy levels of Tm3+:1G4(a),1G4(b).The obtained sensitivity decreases with the increase of Yb3+ions content,which is mainly attributed to the changes in photon absorption process of Tm^3+:1G4(b).