Yanyan Guo

2 μm emission properties and nonresonant energy transfer of Er 3+ and Ho 3+ codoped silicate glasses

2.0 μm emission properties of Er3+/Ho3+ codoped silicate glasses were investigated pumped by 980 nm LD. Absorption spectra were determined. Intense mid-infrared emissions near 2 μm are observed. The spectral components of the 2 μm fluorescence band were analyzed and an equivalent model of four-level system was proposed to describe broadband 2 μm emission. Low OH− absorption coefficient (0.23 cm−1), high fluorescence lifetime (2.95 ms) and large emission cross section (5.61 × 10−21 cm2) corresponding to Ho3+: 5I7→5I8 transition were obtained from the prepared glass. Additionally, energy transfer efficiency from the Er3+: 4I13/2 to the Ho3+: 5I7 level can reach as high as 85.9% at 0.75 mol% Ho2O3 doping concentration. Energy transfer microscopic parameters (CDA) via the host-assisted spectral overlap function were also calculated to elucidate the observed 2 μm emissions in detail. Moreover, the rate equation model between Er3+ and Ho3+ ions was developed to elucidate 2 μm fluorescence behaviors with the change of Ho3+ concentration. All results reveal that Er3+/Ho3+ codoped silicate glass is a promising material for improving the Ho3+ 2.0 μm fiber laser performance.

Optical characterization of Tm3+ doped Bi2O3-GeO2-Ga2O3 glasses in absence and presence of BaF2

In this paper, Two new Bi2O3-GeO2-Ga2O3 glasses (one presence of BaF2) doped with 1mol% Tm2O3 were prepared by melt-quenching technique. Differential thermal analysis (DTA), the absorption, Raman, IR spectra and fluorescence spectra were measured. The Judd–Ofelt intensity parameters, emission cross section, absorption cross section, and gain coefficient of Tm3+ ions were comparatively investigated. After the BaF2 introduced, the glass showed a better thermal stability, lower phonon energy and weaker OH− absorption coefficient, meanwhile, a larger ~1.8 μm emission cross section σem (7.56 × 10−21 cm2) and a longer fluorescence lifetime τmea (2.25 ms) corresponding to the Tm3+: 4F3 → 3H6 transition were obtained, which is due to the addition of fluoride in glass could reduce the quenching rate of hydroxyls and raise the cross-relaxation (3H6 + 3H4 → 3F4 + 3F4) rate. Our results suggest that the Tm3+ doped Bi2O3-GeO2-Ga2O3 glass with BaF2 might be potential to the application in efficient ~1.8 μm lasers system.

Tm 3+ -doped lead silicate glass sensitized by Er 3+ for efficient ~2 μm mid-infrared laser material

Er3+/Tm3+ co-doped lead silicate glasses with low phonon (953cm-1) and good thermal stability were synthesized. The ~2μm mid-infrared emission resulting from the 3F4→3H6 transition of Tm3+ sensitized by Er3+ has been observed by 808nm LD pumping. The optimal luminescence intensity was obtained in the sample with 1Tm2O3/2.5Er2O3 co-doped. Moreover, the energy transfer mechanism from Er3+ to Tm3+ ion was analyzed. Absorption and emission cross section have been calculated. The calculated maximum emission cross section of Tm3+ is 2.689×10-21cm2 at 1863nm. Microparameters of energy transfer between Er3+ and Tm3+ ions have also been analyzed. These results ensure that the prepared Er3+/Tm3+ co-doped lead silicate glasses have excellent spectroscopic properties in mid-infrared region and provide a beneficial guide for mid-infrared laser material.

Intense 2.7 μm emission in Er3 + doped zinc fluoride glass

A novel erbium ion doped zinc fluoride glass was prepared. 2.7μm emission and transmittance properties together with thermal ability were investigated. An enhanced 2.7μm emission was observed by introducing ZnF2 in the ZrF4-based fluoride glass. Meanwhile, the J-O parameters and branching ratios (β) of Er3+-doped zinc fluoride glass were calculated and analyzed. The present Er3+-doped zinc fluoride glass with large emission cross-section (0.92×10-20cm2) and long decay lifetime (2.05ms) at 2.7μm indicates that it have very promising applications for solid state lasers around 3μm.

Positive influence of Ce 3+ on effective transfer Yb 3+ : 2 F 5/2 → Ho 3+ : 5 I 6 in silica-germanate glass for mid-infrared applications

A1.5 time enhancement of a 2.0 μm emission was achieved successfully in Yb3+/Ho3+ doped silica-germanate glass with a 0.1 mol% Ce3+ addition, which possesses a larger emission cross section (4.43 × 10−21 cm2). According to the measured absorption spectra, the Judd-Ofelt parameters and radiative properties were calculated and discussed. The energy transfer mechanisms existed in Ho3+, Yb3+ and Ce3+ ions were investigated based on absorption, upconversion and fluorescence spectra. Meanwhile, the decay profiles of several levels were measured to further examine the enhanced mid-infrared emissions. Moreover, a high energy transfer microscopic parameter (7.54 × 10−40cm6/s) of Yb3+→Ho3+ process was obtained when 0.1 mol% Ce3+ ions were introduced into the Ho3+/Yb3+ system. All results indicate that the Yb3+/Ho3+/Ce3+ tri-doped silica-germanate glass is a promising candidate material for improving the Ho3+ 2.0 μm fiber laser performance.

Spectroscopic properties of Nd3+/Yb3+ co-doped in lithium aluminum silicate glass for 1.0 μm fiber laser

The Nd3+, Yb3+ singly doped and Nd3+ /Yb3+ co-doped lithium aluminum silicate glasses are fabricated by using a conventional melt quenching technique in air atmosphere, with the molar composition of (60-a-b)SiO2-3Al2O3-20Li2O-12MgO-5CaO-aNd2O3-bYb2O3 (with a=0, 0.25, 0.5, 1 and b=0,2). The Spectroscopic properties of 1.0 μm emission and Luminescence lifetime in Nd3+ /Yb3+ co-doped lithium aluminum silicate glasses are investigated under 808 nm excitation. The Judd–Ofelt theory is used to study the spectroscopic properties of Nd3+ . Meanwhile, the emission cross-section of Yb3+ are obtained by using the reciprocity method. A broad emission band from 950 to 1,100 nm is detected when the Nd3+ /Yb3+ co-doped in lithium aluminum silicate glasses excited by 808 nm LD. The energy transfer process from Nd3+ →Yb3+ co-doped in lithium aluminum silicate glasses is described in this paper.

Influence of the synthesis atmosphere on NIR fluorescence behavior of Ce/Er co-doped bismuth glass through valence state changes of cerium

This work investigates the near-infrared emission characteristics and energy transfer between erbium and cerium in bismuth glass by the reaction atmosphere process. The Er3+:1.5μm emission can be successfully enhanced by performing a reduction conversion of Ce4+→Ce3+ using a reducing atmosphere. The discrepancies of the energy structure between Ce3+ and Ce4+ result in a contrasting sensitizing effect on Er3+:1.5μm emission intensity and decay lifetime. The results show that a significant amount of Ce3+ is present in glasses prepared in a reducing atmosphere, whereas Ce4+ is the main species in an oxidizing atmosphere by means of absorption spectra and XPS curves. The reason for upconversion quenching is also discussed.

2.8 μm emission and OH quenching analysis in Ho 3+ doped fluorotellurite-germanate glasses sensitized by Yb 3+ and Er 3+

The use of Yb3+ and Er3+ co-doping with Ho3+ to enhance and broaden the Ho3+: 5I6 → 5I7 ~2.8 μm emissions are investigated in the fluorotellurite-germanate glasses. An intense ~3 μm emission with a full width at half maximum (FWHM) of 245 nm is achieved in the Er3+/Ho3+/Yb3+ triply-doped fluorotellurite-germanate glass upon excitation at 980 nm. The glass not only possesses considerably low OH− absorption coefficient (0.189 cm−1), but also exhibits low phonon energy (704 cm−1). Moreover, the measured lifetime of Ho3+: 5I6 level is as high as 0.218 ms. In addition, the energy transfer rate to hydroxyl groups and quantum efficiency (η) of 5I6 level were calculated in detail by fitting the variations of lifetimes vs. the OH− concentrations. The formation ability and thermal stability of glasses have been improved by introducing GeO2 into fluorotellurite glasses. Results reveal that Er3+/Ho3+/Yb3+ triply-doped fluorotellurite-germanate glass is a potential kind of laser glass for efficient 3 μm laser.