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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]

Sm:YAlO 3 (Sm:YAP) crystal with size of Φ28 × 80 mm3 was grown by Czochralski (Cz) method. Polarized absorption spectra and fluorescence spectra of Sm:YAP crystal were discussed for the first time. The peak emission cross-sections were calculated to be 0.80 × 10−21 cm2 (604 nm for a-polarization), 1.82 × 10−21 cm2 (604 nm for b-polarization) and 1.63 × 10−21 cm2 (610 nm for c-polarization), respectively. The Judd-Ofelt (JO) intensity parameters were calculated to be Ω 2 = 2.59 × 10−20 cm2, Ω 4 = 1.78 × 10−20 cm2 and Ω 6 = 2.98 × 10−20 cm2, respectively. The decay lifetime of 4G 5/2 energy level was measured to be 2.51 ms. All above results indicate the Sm:YAP crystal may be a potential candidate of reddish-orange laser pumped directly by the GaN/InGaN laser diode. • Sm:YAlO 3 crystal was grown by Cz method. • Polarized optical spectra of Sm:YAlO 3 crystal were investigated. • The transitions of 4G 5/2 → 6H 7/2 have the highest branching ratio value, which is suitable for reddish-orange laser. [ABSTRACT FROM AUTHOR]

Tm3+-doped calcium niobium gallium garnet (Tm:CNGG) single crystals have been successfully grown by the micro-pulling-down (μ-PD) method. The crystal structure, absorption spectra, fluorescence spectra and lifetimes of Tm:CNGG crystals were investigated. The absorption and emission bandwidths of Tm:CNGG crystals are larger than those of other Tm3+ doped garnet crystals, which will be beneficial for laser diode (LD) pumping and ultrashort pulse generation. Additionally, continuous wave (CW) laser operation around 2 μm was achieved in the 2.0 at.% Tm:CNGG crystal by LD pumping. [ABSTRACT FROM AUTHOR]

Pr 3+ -doped YAlO 3 (YAP) single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption and polarized fluorescence spectra were measured at the room temperature. The spectroscopic parameters based on the polarized absorption spectra were calculated by Judd-Ofelt (J-O) theory for the first time. The fluorescence lifetime of 3 P 0 energy level was fitted to be 19.16 μs with the quantum efficiency of 95.8%. Through the analyzing of the spectroscopic properties, Pr:YAP crystal was demonstrated to be a promising candidate for solid state laser operation. [ABSTRACT FROM AUTHOR]

Yb,Tb:YAG crystals with various Yb3+ and Tb3+ concentration were grown by the micro-pulling-down method (μ -PD). The absorption spectra, fluorescence spectra and fluorescence decay curves of Yb,Tb:YAG crystals were measured at room temperature. Under 980 nm excitation, Yb,Tb:YAG crystals exhibited intense visible up-conversion luminescence due to the cooperative energy transfer from two Yb3+ ions to one Tb3+ ion. Under 485 nm excitation, Yb,Tb:YAG crystals yielded near-infrared down-conversion emission, ascribing to the cooperative absorption of pumping photons and cooperative energy transfer from one Tb3+ ion to two Yb3+ ions. The energy transfer processes from Yb3+ ions to Tb3+ ions were discussed, and the energy transfer efficiency was calculated. Based on studies of the obtained results, Yb3+/Tb3+ co-doped YAG crystal shows promising potential for sensing, volumetric displays, optical data storage, light emitting diodes. • Yb,Tb:YAG single crystals grown by the micro-pulling-down technique. • The cooperative energy transfer process was analyzed. • The effect of doped concentration on energy transfer efficiency was discussed. [ABSTRACT FROM AUTHOR]

Tm3+ doped and Tm3+, Pr3+ co-doped Lu 3 Al 5 O 12 (LuAG) garnet single crystals have been successfully grown by the micro-pulling-down (μ-PD) method. The absorption spectra, fluorescence spectra and lifetimes were investigated at room temperature. In the absorption spectra, the transition centered at 782 nm matches well with the GaAlAs LDs laser pumping. The incorporation of Pr3+ into Tm3+-doped LuAG crystals enhanced the intensity of 1.5 μm emission and decreased the fluorescence lifetime of the lower energy level for 1.5 μm emission from 10.427 ms to 2.603 ms. The results indicate that Tm,Pr:LuAG crystal can be promising candidate for near infrared 1.5 μm laser materials. • Tm:LuAG and Tm,Pr:LuAG crystals have been successfully grown by the micro-pulling-down (μ-PD) method. • Spectral parameters of Tm:LuAG and Tm,Pr:LuAG crystals were obtained and compared. • The fluorescence mechanism of Tm,Pr:LuAG crystal has been studied for the first time. [ABSTRACT FROM AUTHOR]

GdScO 3 single crystal codoped with Tm3+ and Tb3+ ions was successfully grown by the Edge-defined Film-fed Growth Method (EFG) for the first time. Absorption, fluorescence spectrum and fluorescence lifetimes of the grown crystal at room temperature were measured. The absorption cross-section at 789 nm was calculated to be 8.20 × 10−21 cm2. The emission cross-section was 1.35 × 10−21 cm2 at 1504 nm with the FWHM of 95.3 nm. The fluorescence lifetimes of the 3H 4 state and the 3F 4 state were fitted to be 253 μs and 1460 μs, respectively. Compared with Tm3+ single doped GdScO 3 crystal, the codoping of Tb3+ successfully depopulated the 3F 4 energy level and enhanced the emission at 1.5 μm region. It indicated that Tm,Tb:GdScO 3 could be favorable laser medium for 1.5 μm-laser operation. • Tm3+ and Tb3+ co-doped GdScO 3 crystal was successfully grown by the edge-defined film-fed method (EFG) for the first time. • Spectral parameters and Judd-Ofelt parameters of Tm,Tb:GdScO3 crystal were obtained and compared. • The fluorescence mechanism of Tm3+ and Tb3+ co-doped GdScO 3 crystal has been studied. [ABSTRACT FROM AUTHOR]

Photograph of Yb,Ho:YAG crystals grown by the μ-PD method. (a) Yb = 0.05, (b) 0.1, (c) 0.15. • Y 3 Al 5 O 12 (YAG) single crystals doped with a fixed Ho3+ content of 0.5 at.% and various Yb3+ contents (Yb = 5, 10 and 15 at.%) have been successfully grown by the micro-pulling-down (μ-PD) method. Y 3 Al 5 O 12 (YAG) single crystals doped with a fixed Ho3+ content of 0.5 at.% and various Yb3+ contents (Yb = 5, 10 and 15 at.%) have been successfully grown by the micro-pulling-down (μ-PD) method. The absorption spectra, fluorescence spectra and fluorescence decay curves were recorded at room temperature. The intense emission of Yb,Ho:YAG crystal centered at 2 μm corresponds to the 5I 7 → 5I 8 transition. Three intense emissions centered at 524–569 nm, 623–691 nm and 744–746 nm, correspond to the 5F 4 + 5S 2 → 5I 8 , 5F 5 → 5I 8 and 5F 4 + 5S 2 → 5I 7 transitions, respectively. The possible energy transfer mechanisms were discussed intensively. [ABSTRACT FROM AUTHOR]

Dy3+-doped Y 3 Al 5 O 12 (YAG) and Y 3 ScAl 4 O 12 (YSAG) single crystals have been successfully grown by the micro-pulling-down (μ-PD) technique for the first time. The room temperature absorption spectra, fluorescence spectra and fluorescence decay curves were measured. Dy:YAG and Dy:Y 3 ScAl 4 O 12 crystals exhibit strongest emission centered at 583 nm, corresponding to the 4F 9/2 → 6H 13/2 transition. The decay lifetime of the 4F 9/2 level was measured to be 634 μs and 667 μs, respectively. All these results indicate that the Dy:YAG and Dy:Y 3 ScAl 4 O 12 crystals are promising candidates for yellow laser operation. • Dy:YAG and Dy:YSAG crystals were grown by the micro-pulling-down method. • Dy:YAG and Dy:YSAG crystals exhibit strong emission centered at 583 nm. • Dy:YSAG crystal has a wide emission bandwidth due to the disordered crystalline structure. [ABSTRACT FROM AUTHOR]