Investigation on energy transfer from Er^3＋ to Nd^3＋ in tellurite glass

A study of energy transfer of Er^3＋/Nd^3＋ codoped tellurite glasses was presented. By Nd^3＋ co-doping, both the Er^3＋ green emission corresponding to the Er^3＋： （^4S3/2, ^2H11/2）→^4I15/2 transitions and the red emission corresponding to the Er^3＋： ^4F9/2→^4I15/2 transitions were quenched. The energy transfer mechanism between Er^3＋ and Nd^3＋ was discussed based on their energy level characteristics. The interaction parameters, CO-A, for the energy transfer processes from Er^3＋ to Nd^3＋ in tellurites glass were calculated. Finally, the resonant transfer Er^3＋： ^4I9/2→Nd^3＋： （^4F5/2, ^2H9/2） was proposed to be the most probable microscopic process to occur in contrast with the other processes.     

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 per-fectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion proc-esses between Tm3 and Yb3 under direct pumping of 975 nm LD. The spectra and lifetimes of Tm3 fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and inten-sity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping proc-ess. The potential advantages of Tm3 /Yb3 co-doped tellurite glass as amplifier material were concluded.     

Fabrication and gain performance of Er^3＋/Yb^3＋-codoped tellurite glass fiber

Er^3＋/Yb^3＋-codoped TeO2-ZnO-BaO-La2O3 tellurite glass fiber was fabricated by rotation and rod-in-tube technologies. The thermal stability and optical refractive index of the core and cladding glasses were determined by DTA and optical coupler, respectively. The average background loss of tellurite glass fiber was 1.8 dB/m at 1310 nm. Optical microscopy and field emission scanning electron microscope （FESEM） were used to study structural characteristics of preforms and optical fibers. The main loss of tellurite glass fiber could be attributed to scatter centre due to core-cladding interface defects. The amplifier performance of tellurite glass fiber was investigated by pumping with 980 nm laser diode （LD）. The gain coefficient and maximum signal gain were 0.21 dB/mW and 10 dB, respectively, for a pumping power of 120 mW. Gains exceeding 5 dB were obtained over 30 nm bandwidth from 1535 to 1565 nm. The minimum noise figure was 4.8 dB at 1557 nm.     

Influence of B2O3 on Spectroscopic Properties of Er^3＋/Yb^3＋ Co-Doped Tungsten-Tellurite Glasses

A series of novel Er^3＋/Yb^3＋ co-doped （85- x ） TeO2-15WO3-xB2O3 （TWB;x=2%,5%,8%（mole fraction） ） glasses were prepared. Influence of B203 on the spectroscopic properties of Er^3＋/Yb^3＋ co-doped tungsten-tellurite glasses were investigated. It is found that the intensity of 1.5μm fluorescence, lifetime of the ^4I13/2 level and upconversion fluorescence all decrease with the increase of B2O3 content. The product of full width at half maximum （FWHM） and stimulated emission cross-section （σe^peak） of Er^3＋ ：^4I13/2→^4I15/2 transition has an optimum when B203 is 5% （mole fraction）. The emission spectra of Er^3＋ ： ^4I13/2→^4I15/2 transition was analyzed using peak-fit routine, and an equivalent four-level system was proposed to estimate the stark splitting for the 411512 and ^4I13/2 levels of Er^3＋ ions in TWB glasses at room temperature.     

Spectral properties and energy transfer of Tm^3＋/Ho^3＋-codoped Ga2O3-Bi2O3-GeO2-PbO glasses

The 2.0 μm emission originating from Ho^3＋：^5I7→^5I8 were investigated upon excitation with 808 nm laser diode （LD） transition in Ho^3＋/Tm^3＋-codoped gallate-bismuth-germanium-lead glasses Energy transfer （ET） process between Tm^3＋： ^3F4 level and Ho^3＋： ^5I7 level was also discussed. It was noted that the measured peak wavelength and stimulated emission cross-section of Ho^3＋-doped bismuth-germanium-lead glasses were -2.02 μm and 5.1×10^-21 cm^2, respectively. Intense emission of Ho^3＋ in Tm^3＋/Ho^3＋-codoped GBPG glass were observed, which resulted from the ET between Tm^3＋： ^3F4 and Ho^3＋： ^5I7 level upon excitation with 808 nm LD.     

Spectroscopic Properties of Er^3＋-Doped TeO2-WO3-ZnO-ZnF2 Glasses

The Er^3 -doped TeO2-WO3-ZnO-ZnF2(TWZOF) glasses were prepared. The absorption spectra, 1.5μm emission spectra and fluorescence lifetimes of Er^3 , excited at 970nm, were measured. The J-O parameters Ωt(t=2, 4, 6), absorption and emission cross-sections were calculated. The dependence of the 1.5μm emission intensity, fluorescence lifetime and bandwidth of the Er^3 emission upon the contents of ZnF2 in glass were investigated. In TWZOF glass, Er^3 ions had a broad emission profile around 1.5μm with the maximum FWHM of 83nm. With the increasing of the content of ZnF2, the emission intensity at peak wavelength and the fluorescence lifetime of Er^3 at 1.5μm increase.     

50GeSe_2-25In_2Se_3-25CsI glass doped with Tm~(3+),Tm~(3+)/Ho~(3+) and Tm~(3+)/Er~(3+) foramplifiers working at 1.22 μm

Se-based chalcohalide glass of 50GeSe2-25In2Se3-25CsI was prepared.The thermal and optical characterizations revealed that thishost was thermally and optically superior for practical applications.Strong emission centered at 1.22 μm was observed in all Tm3+ single-doped,Tm3+/Ho3+ and Tm3+/Er3+ co-doped samples with an excitation of 808 nm wavelength.The emission was attributed to the Tm3+:3H5→3H6 transition.The co-doping of Ho3+ or Er3+ largely broadened the width and slightly strengthened the intensity of t...     

Tm3+-doped tellurite glass with Yb3+ 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 per-fectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion proc-esses between Tm3+ and Yb3+ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm3+ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and inten-sity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping proc-ess. The potential advantages of Tm3+/Yb3+ co-doped tellurite glass as amplifier material were concluded.     

2 μm mid-infrared optical spectra of Tm3+-doped germanium gallate glasses

Glasses with the composition of 65GeO212Ga2O3-10BaO-8Li2O-5La2O3(molar ratio) doped with 1.526 wt.%, 3.006 wt.%, 5.836 wt.%, 11.028 wt.%, and 15.678 wt.% Tm2O3, respectively, were fabricated by conventional melting method. According to the absorption spectra and the Judd-Ofelt theory, the J-O strength parameters (Ω2,Ω4, Ω6) were calculated, with which the radiative transition probabilities,branching ratios and radiative lifetimes were obtained. The infrared emission spectra (with 808 nm LD excitation) at～1.47 and～1.8 μm of various concentrations of Tm3+-doped glasses were studied. The emission intensity at～1.8 μm reached to the maximum when the Tm2O3-doping concentration was near to be～3.006 wt.% (1.0 mol.%), and then decreased as doping concentration increased further. The mechanism of the fluorescence intensity change was explained with the cross-relaxation effect and the concentration quenching effect of Tm3+. Meanwhile, according to McCumber theory, the absorption and emission cross-sections corresponding to the 3F4→3H6 transitions of Tm3+ at 1.8 μm was obtained. For Tm3+-doped germanate glasses, the maximum emission cross-section reached a value higher than that re-ported for fluorozircoaluminate glasses. It is expected to be a favorable candidate host for～2.0 μm mid-inflated laser because the glass shows favorable optical spectra.     

Up-conversion luminescence of Er~（3＋）-doped and Yb~（3＋）/Er~（3＋） co-doped 12CaO·7Al_2O_3 poly-crystals

The optical properties of Er3+-doped and Yb3+/Er3+ co-doped 12CaO·7Al2O3 (C12A7) poly-crystals, synthesized by high temperature solid state method, were investigated in detail. For Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals, two main emission bands centered around 530/550 nm (green) and 660 nm (red) were observed under 980 nm diode laser excitation via an up-conversion process. The intensity of green up-conversion emission had a strong increase in Er3+ (1.0 mol.%, 1.5 mol.%, 3.0 mol.%), and the intensity ratio of red to green up-conversion emission had an increase in Yb3+ (1.0 mol.%, 2.0 mol.%, 10. 0 mol.%)/Er3+ (fixed at 1.0 mol.%). This detailed study of the up-conversion processes allowed us to identify the dominant up-conversion mechanisms in Er3+-doped and Yb3+/Er3+ co-doped C12A7 poly-crystals.     

Photoluminescent properties of Ca2RE8（SiO4）6O2：A （RE=Y,Gd; A=Pb^2＋, Mn^2＋） phosphor films prepared by sol-gel process

Ca2RE8（SiO4）6O2：A （RE=Y, Gd; A=Pb^2＋, Mn^2＋） phosphor fdms were dip-coated on quartz glass substmtes through the sol-gel process. X-ray diffraction （XRD）, photoluminescence （PL） spectra as well as lifetimes were used to characterize the resulting films. Under short wavelength UV excitation, the film showed a red emission with medium intensity. The decay curve of Mn^2＋ luminescence in Ca2Gd8（SiO4）6O2：Pb Mn film could be fitted into a single exponential function. The lifetime of Mn^2＋ was 10.21 ms in Ca2Gd8（SiO4）6O2.     

Three-photon-excited fluorescence of Tb-doped CaO-Al2O3-SiO2 glass by femtosecond laser irradiation

A near infrared to visible blue, green, and red upconversion luminescence in a Tb^3＋-doped CaO-Al2O3-SiO2 glass was studied, which was excited using 800 nm femtosecond laser irradiation. The upconversion luminescence was attributed to ^5D3→^7F5, ^5D3→^7F4, ^5D3→^7F3, ^5D4→^7F6, ^5D4→^7F5, ^5D4→^7F4, and ^5D4→^7F3 transitions of Tb^3＋. The relationship between upconversion luminescence intensity and the pump power indicated that a three-photon simultaneous absorption process was dominant in this upconversion luminescence. The intense red, green, and blue upconversion luminescence of Tb^3＋-doped CaO-Al2O3-SiO2 glass may be potentially useful in developing three-dimensional display applications.     

Catalytic combustion of toluene over Pd-based monolithic catalysts with a novel washcoat Ce0.8Zr0.15La0.05Oδ

Two novel washcoats Ce_0.8Zr_0.15La_0.05O_δ and Ce_0.8Zr_0.2O₂ was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate and Pd/Ce_0.8Zr_0.2O₂/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H₂-temperature-programmed reduction (H₂-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La³⁺ into CeO₂-ZrO₂ solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO₂-ZrO₂ solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce_0.8Zr_0.15La_0.05O_δ had much better redox properties. The reductive temperature of Ce⁴⁺ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce_0.8Zr_0.15La_0.05O_δ had better thermal stability than the washcoat Ce_0.8Zr_0.2O₂, the developed Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.