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A series of high quality x%Pr3+:BaF2 (x = 0.6, 1, 2); (1%Pr3+, 2%Na+):BaF2; (1%Pr3+, y%Ca2+):BaF2 (y = 3, 5) and (0.6%Pr3+, 10%R3+):BaF2 (R = Y, Lu, Gd) crystals were grown by temperature gradient technique (TGT). The Raman spectra, absorption spectra, fluorescence spectra, and fluorescence decay lifetime were measured. XRD patterns indicate that the as-synthesized samples are pure BaF2 phase. The absorption cross-section of Pr3+ ions in the BaF2 matrix can be greatly improved by co-doping R3+ ions, while improvement by Na+ and Ca2+ ions is marginal. The fluorescence characteristic of Pr3+ ions can be effectively regulated by co-doping Na+, Ca2+, R3+ (R = Y, Lu, Gd) ions of different valence states. When R3+ ions are introduced, the fluorescence spectra show the strongest orange emission and the CIE chromaticity coordinates of Pr3+ ions are also in the orange region. When single-doped Pr3+ ions and Na+ or Ca2+ ions are introduced, the fluorescence lifetime of the 3P0 level is double exponential decay, and the short lifetime is the main proportion. However, the fluorescence centers tend to homogeneous and stable by R3+ ions co-doping and the fluorescence lifetime exhibits single-exponential decay, which is fitted to 49.7 μs, 47.8 μs and 49.6 μs of (0.6%Pr3+, 10%R3+):BaF2 (R = Y, Lu, Gd), respectively. All the results show that (Pr3+, Gd3+):BaF2 and (Pr3+, Na+):BaF2 are excellent laser gain media for high-efficiency orange and red laser operation. [ABSTRACT FROM AUTHOR]

• A series of 0.6 at% Pr:CaF 2 -RF 3 (R= Y3+, Gd3+, Lu3+) crystals were successfully grown by the temperature gradient technique(TGT) method. • By co-doping R3+ ion (R=Y3+, Gd3+, Lu3+), the spectral performance of the crystals could be significantly improved and the function effect is also different. • The spectral performance and spectral quality factor of the crystals were systematically described and compared for the first time. • The spectral modulation effect caused by Y3+, Gd3+ and Lu3+ co-doping ion was discussed. A series of 0.6 at% Pr:CaF 2 -RF 3 (R = Y3+, Gd3+, Lu3+) crystals have been successfully grown by the temperature gradient technique(TGT). The absorption spectra, fluorescence spectra, and fluorescence decay curves were measured and analyzed at room temperature. When the R3+ concentration is higher than a certain value, the diffraction peaks of Pr:CaF 2 -RF 3 crystals were well indexed to the (Ca,Y)F 2 phase. By co-doping R3+ ion (R=Y3+, Gd3+, Lu3+), the spectral performance of the crystals could be significantly improved and the function effect is also different. For 0.6 at% Pr, 28.5 at% Y:CaF 2 crystal, the fluorescence lifetime of 3P 0 energy level was fitted to be 45.46 µs, and the emission cross sections of 3P 0 →3H 6 (605 nm), and 3P 0 →3F 2 (641 nm) were calculated to be 1.78 × 10−20 cm2, and 4.61 × 10−20 cm2 with the full width at half (FWHM) of 20.1 nm and 6.8 nm, respectively. The 0.6 at% Pr, 28.5 at% Y:CaF 2 crystal could be favorble laser medium for ultra-fast laser opreration at 605 nm and 641 nm. For 0.6 at% Pr, 18 at% Gd:CaF 2 and 0.6 at% Pr, 10 at% Lu:CaF 2 crystals, the spectral quality factors σ em• τ f of 3P 0 →3F 2 transition (642 nm) were calculated to be 614.18 × 10−20 cm2•µs and 506.36 × 10−20 cm2•µs with the FWHM of 3.7 nm and 5.3 nm. All the results show that 0.6 at% Pr, 18 at% Gd:CaF 2 and 0.6 at% Pr, 10 at% Lu:CaF 2 crystals are promising gain media for high-efficiency visible laser output at 642 nm, which would compete with commercial Pr: YLF crystal in the future. [ABSTRACT FROM AUTHOR]

Yb,Pr:CaF 2 crystals have been grown successfully by the temperature gradient technique(TGT). The absorption spectra, fluorescence spectra, fluorescence decay lifetime of Pr3+ ions in CaF 2 crystal sensitized by different Yb3+ ions concentration have been measured. The effective J-O intensity parameters were fitted to be Ω 2 =0.36 × 10−20cm2, Ω 4 =2.89 × 10−20cm2, Ω 6 =6.69 × 10−20cm2 for 0.3 at.%Pr,1.5 at.%Yb:CaF 2. And the emission cross sections of 3P 1 →3H 5 (535 nm), and 3P 0 →3F 4 (750 nm) are calculated to be 2.02 × 10−20cm2, and 2.50 × 10−20cm2 with the FWHM of 17.2 nm, and 10.5 nm, respectively. The fluorescence lifetime of 3P 0 has achieved great increasing by sensitizing of Yb3+ ion. Not only the up-conversion luminescence can be achieved, but also the broad band emission from 1D 2 energy level can be observed. The results show that Yb,Pr:CaF 2 could be a potential laser gain medium for visible and near-IR laser operation. • Not only the up-conversion luminescence can be achieved, but also the broad band emission from 1D 2 energy level can be observed by Yb3+ ion sensitizing. • Spectral properties and Judd-Ofelt parameters of Yb,Pr:CaF 2 crystal were investigated and analysed. [ABSTRACT FROM AUTHOR]

Yb,Ho:Y 2 O 3 ceramics have been fabricated by Spark Plasma Sintering method (SPS). The microstructure and transmittance of the ceramics sintered from 1623 K to 1673 K were analyzed. The highest in-line transmittance of Yb,Ho:Y 2 O 3 ceramic sintered at 1673 K reached almost 83% at 750 nm with the thickness of 1 mm. The absorption spectra, fluorescence spectra and fluorescence decay curve were recorded at room temperature. The Judd-Ofelt parameters Ω 2 , Ω 4 and Ω 6 were calculated to be 8.33 × 10−20 cm2, 1.81 × 10−20 cm2, and 0.82 × 10−20 cm2, respectively. The intense emission cross section of Yb,Ho:Y 2 O 3 ceramic was 3.43 × 10−20 cm2 at 2057 nm with full width at half maximum (FWHM) of 208 nm. The results indicate that Yb,Ho:Y 2 O 3 transparent ceramic can be a promising laser gain medium for laser operation around 2 μm. Image 1 • The highest in-line transmittance of Yb,Ho:Y 2 O 3 ceramic sintered at 1673 K reached almost 83% at 750 nm with the thickness of 1 mm. • The spectral characteristics were intensively investigated through Judd-Ofelt theory. [ABSTRACT FROM AUTHOR]