Na5Lu9F32 Single Crystals Research Articles

Infrared spectroscopic characterization of Na5Lu9F32 single crystals doped with various Er3+ concentrations

This work reports on optical spectra of Na5Lu9F32 single crystals doped with various Er3+ concentrations from 0.5 to 5 mol%. In our improved Bridgman method, the X-ray powder diffractions were investigated and optical parameters were also calculated by the Judd–Ofelt theory. Results showed that Er3+ ions entered the Lu3+ sites successfully without causing any obvious peak changes, and the doping concentration of Er3+ had important influence on the Er3+ local structure in Na5Lu9F32 crystals. The maximum emission intensities of ~1.5 and ~2.7 μm were obtained in present research when the doping concentration of Er3+ were 4 and 5 mol%, respectively, under the excitation of 980 nm LD. In these doping concentration, the maximum emission cross-sections were calculated to be 1.37 × 10−20 cm2 (~1.5 μm) and 2.1 × 10−20 cm2 (~2.7 μm). The gain cross-section at 2.7 μm was also estimated according to the absorption and emission cross section spectra. All these spectroscopic characterizations suggested that this fluoride crystal would possess promising applications in infrared lasers.

Enhanced luminescence at 2.7 μm of Na5Lu9F32 single crystals co-doped Er3+/Pr3+ grown by Bridgman method.

Na5Lu9F32 single crystals co-doped with 1 mol. % Er3+ and various concentrations (0.1 mol. %, 0.3 mol. %, 0.5 mol. %, 0.7 mol. %, and 1 mol. %) of Pr3+ were successfully grown using the Bridgman method. Optical spectroscopic investigations of the obtained single crystal were reported for the absorption, emission, and luminous decay. The obtained single crystal appears with almost no absorption at the 2.7 μm band, attributable to the OH- bond. According to the Judd-Ofelt (J-O) theory, the J-O intense parameters of Er3+ ions were calculated. Under the 980 nm LD pumping, an obviously enhanced emission at 2.7 μm was obtained in the Er3+/Pr3+ co-doped crystal compared with the Er3+ singly doped crystal due to the energy transfer from Er3+ to Pr3+. The most intense emission at 2.7 μm was obtained when the doping concentrations of Er3+ and Pr3+ were 1 mol. % and 0.5 mol. % in the present research. The maximum emission cross-section and gain cross-section at 2.7 μm were also estimated. Moreover, using the Dexter theory, the energy transfer microscopic parameters have been calculated, and the decay curve fitting using the Inokuti-Hirayama expression indicated the dipole-dipole energy transfer from Er3+ to Pr3+ ions.

Luminescence properties of Er3+/Nd3+ co-doped Na5Lu9F32 single crystals for 2.7 μm mid-infrared laser

The enhanced 2.7 μm mid-infrared emission from the Er3+:4I11/2 → 4I13/2 transition with Nd3+ ions as the sensitizer was achieved in the Na5Lu9F32 single crystal which was successfully grown by a Bridgman method. The transmission spectrum was tested and almost no absorption of 2.7 μm band was observed. It was indicated that the content of OH- ion was very low in the crystal and it was beneficial to the 2.7 μm mid-infrared laser output. Intense 2.7 μm emissions were achieved with Nd3+ ions sensitizing Er3+ ions under the 800 nm LD pumping and the energy transfer processes between Er3+ and Nd3+ ions were analyzed. Meanwhile, the greatly decreased near infrared emission at 1.5 μm and green up-conversion emission were obtained. Additionally, the optimized concentration ratio of Er3+ to Nd3+ for efficient 2.7 μm emission was investigated in this work and the maximum emission cross section at 2.7 μm was calculated. The decay curve of 1.5 μm emission could be well fitted by Inokuti-Hirayama expression, which was strongly indicated the dipole-dipole energy transfer from Er3+ to Nd3+ ions. The results showed that Er3+/Nd3+ co-doped Na5Lu9F32 single crystal had potential applications in 2.7 μm mid-infrared laser.

Cooperative Energy Transfer Up-/Down-Conversion Luminescence in Tb3+/Yb3+ Co-Doped Cubic Na5Lu9F32 Single Crystals by Gd3+ Co-Doping

The luminescence properties of Na5Lu9F32 single crystals tridoped Tb3+, Yb3+, and Gd3+ ions synthesized via a vertical Bridgman method were reported. Gd3+ was codoped as a sensitizer in Na5Lu9F32:Tb3+, Yb3+, thus increasing the absorption line-width and the absorption cross sections in the ultraviolet–visible region. Effects of Gd3+ concentration on the luminescence properties under ultraviolet and near-infrared were investigated. The energy transfer mechanism between the Gd3+and Tb3+ ion was witnessed by the detailed analyses of the excited-state lifetimes, emission quantum yields, and emission and excitation spectra for the Na5Lu9F32:Tb3+, Yb3+ single crystals codoping with various Gd3+ concentrations ranging from 0 to 0.25 mol %. Following the excitation light in ultraviolet region, Na5Lu9F32 single crystals tridoped Tb3+/Yb3+/Gd3+ showed dominant green emissions in the visible region and at 980 nm which were attributed to 5D4 → 7F5 transition of Tb3+ and 2D5/2 → 2F7/2 of Yb3+, respectively. Under the ...

Infrared optical characterization and energy transfer of Na5Lu9F32 single crystals co-doped with Er3+/Tm3+ grown by Bridgman method

This paper reported on successful preparation of Na5Lu9F32 single crystals co-doped with ∼2mol% Er3+ and various Tm3+ concentrations from 0.7mol% to 3.2mol% by Bridgman method. The J-O intensity parameters of Er3+ were calculated and analyzed according to the absorption spectra. The fluorescence decay curve at Er3+:4I13/2 level was measured to investigate the luminescent properties of the Er3+/Tm3+ co-doped Na5Lu9F32, and the energy transfer process between Er3+ and Tm3+. An intense 2.7μm emission was achieved with Tm3+ ions sensitizing Er3+ ions under the 800nm LD pumping. The maximum emission intensity at 2.7μm was obtained at about 3.2mol% doping concentration of Tm3+ when the concentration of Er3+ ions was fixed at ∼2mol% in the current research. The calculated maximum value of emission cross section at 2.7μm was 2.22×10−20cm2, and energy transfer efficiency from Er3+:4I13/2 to Tm3+:3F4 was 78%. The electric dipole-dipole interaction was dominant for the energy transfer from Er3+ to Tm3+ ions by using Inokuti-Hirayama’s model.

The optical properties of Tm3+ doped Na5Lu9F32 single crystal

Tm3+ doped Na5Lu9F32 single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters Ω t (t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na5Lu9F32 single crystal. The stimulated emission cross-section of the 3F4→3H6 transition (~1.8 μm) is 0.35×10-20 cm2 for Tm3+ doped Na5Lu9F32 single crystal. The emission spectra under the excitation of 790 nm laser diode (LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm3+ doped Na5Lu9F32 single crystal. The research results show that the Tm3+ doped Na5Lu9F32 single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm3+doped Na5Lu9F32 crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.

Fluorescence spectra of Na5Lu9F32 single crystals co-doped with Ho3+/Tm3+ grown by Bridgman method

This work presents the luminescent properties of Ho3+/Tm3+ co-doped Na5Lu9F32 single crystals that were grown by an improved Bridgman method for the first time. The J–O intense parameters of Ho3+ ions were calculated. An intense 2.0μm emission was achieved with Tm3+ ions sensitizing Ho3+ ions by the processing of energy transfer from Tm3+ ions to Ho3+ ions under excitation of 800nm LD. The maximum emission intensity at 2.0μm is obtained, and the cross sections of Tm3+ ions and Ho3+ ions were calculated. The physical mechanism for energy transfer from Tm3+ to Ho3+ ions was analyzed by using Inokuti–Hirayama’s model.