In order to explore and develop new crystal materials in the 2.7-3.0 mu m band, Pr, Yb, Ho:GdScO3 crystal are successfully grown by the Czochralski method for the first time. X-ray diffraction measurement is performed to obtain powder diffraction data. Raman spectra aree measured and the vibration peaks are identified. The transmission spectrum, emission spectrum and fluorescence lifetime of Pr, Yb, Ho:GdScO3 crystal are also characterized. The center of the strongest absorption band is at 966 nm with a half-peak width of 90 nm, which comes from the transition of Yb3+: F-2(7/2) -> F-2(5/2). The absorption cross section of Yb3+ is calculated and the values at 966, 973, 985 nm are 0.62x10(-20), 0.60x10(-20) and 0.58x10(-20) cm(2) respectively. The maximum emission peak is at 2850 nm and the half-peak width is 70 nm, the lifetimes of Ho3+:I-5(6) and I-5(7) are measured to be 1094 and 56 mu s respectively, and the emission cross section at 2850 and 2935 nm are calculated to be 3.6x10(-20) cm(2) and 1.21x10(-20) cm(2), respectively. Comparing with Yb, Ho: GdScO3 crystal, the absorption peak of Yb3+ and the emission peak are both broadened, which are related to the increase of crystal disorder. The lifetime of the lower energy level decreases significantly. Furthermore, the energy transfer mechanism between and Pr3+ is analyzed, and the energy transfer efficiency between Ho3+:I-5(7) and Pr3+:F-3(2)+H-3(6) is calculated to be 99%, which is higher than those in other materials. All the results show that Pr, Yb, Ho:GdScO3 crystal is an excellent 2.73 mu m laser material, and is easier to achieve laser output than Yb, Ho:GdScO3 crystal.

The melting point of Ti:MgAl2O4 crystal is as high as 2130 °C, it is a challenge to obtain a large-sized and high-quality laser crystal. By optimizing the crystal growth process, Ti:MgAl2O4 crystal with a size of 30 mm× 70 mm is successfully grown by the Czochralski method under the condition of weak reducing atmosphere. The X-ray diffraction pattern is studied, and the x-ray rocking curve indicates that the grown crystal has a high crystalline quality in terms of the lower full width at half maximum(FWHM) intensity, which provides a material basis for the next laser output experiment. In a range of 100–1000 cm–1, there are four Raman vibration peaks located at 312, 410, 675 cm–1 and 771 cm–1 respectively. The grown crystal has an absorption cutoff range of 250–318 nm and two wide absorption bands of 395–495 nm and 550–1100 nm. Excited by 271 nm, the grown crystal shows a strong broadband emission ina range of 340–650 nm with a peak centered at 480 nm. After annealing in hydrogen atmosphere, shape of the transmittance spectrum and emission spectrum are both unchanged, but the fluorescent emission intensity is significantly reduced. After annealing in air atmosphere, the original two absorption bands disappear while none of the characteristics of fluorescence emission in a 340–650 nm range changes significantly. In addition, a new fluorescence emission peak near 725 nm is observed. Combining with the ESR spectrum, what we canconfirm is that the Ti:MgAl2O4 as-grown crystal contains Ti3+ and Ti4+ ions, and no ESR signal of Ti3+ is observed after annealing in air atmosphere. Moreover, excitationspectrum is also recorded. The fluorescence lifetime is 14 μs at room temperature, which is 4–5 times that of Ti:Al2O3 crystal and Ti:BeAl2O4 crystal. Furthermore, the emission cross section of the grown Ti:MgAl2O4 crystal is calculated from the Füchtbauer-Ladenburg (F-L) formula and its value is 2 × 10–20 cm2, large emission cross section which is beneficial for realizing laser oscillation. All the above results show that the Ti:MgAl2O4 crystal is a potential crystal material for realizing broadband tunable blue laser output.

Since the first stimulated optical radiation in ruby crystal laser was devised by Maiman in 1960[1], lasers have undergone a rapid development for over half a century. In 1964, especially, continuous wave (CW) laser oscillation was successfully generated using an Nd:YAG crystal[2], and after that CW laser technology and laser gain materials has attracted tremendous attentions, which affects the application and development of lasers. In addition to CW lasers, Q-switching and mode-locking regimes are also developed rapidly for the generation of short pulse and ultrashort pulse lasers[3-6]. Nd 3+ , Abstract:

用提拉法成功生长出3种不同掺Eu3+浓度的优质Yb,Er,Eu∶YAP激光晶体,并对其光谱特性进行了研究.测量了晶体在320～3 000 nm波段内的吸收光谱,晶体在978 nm附近有强的吸收峰和宽的吸收带.用波长为975 nm的LD连续激光和OPO光参量脉冲激光激发分别获得了晶体的稳态和瞬态荧光光谱,采用单指数衰减拟合得到2.7～3.0 μm激光上下能级寿命.与单掺Er:YAP晶体的光谱参数进行了比较,对yb3+的敏化及Eu3+的退激活机理进行了分析.结果表明,yb3+和Eu3+可分别作为Er3+的敏化剂和退激活剂,增宽978 nm附近的吸收带和降低激光下能级(4 I13/2)与上能级(4 I11/2)寿命的比值(4.1,3.1和2.7);而在单掺Er∶YAP晶体,下能级与上能级寿命的比值高达10.8,不利于激光性能的提高.因此,Yb,Er,Eu∶YAP是一种更适合LD泵浦,有望实现低阈值、2.7～3.0 μm高效率激光输出的新型激光晶体.

Ho:LuGG single crystal was successfully grown by the Czochralski growth method, and its lattice parameter was found to be 12.2371 angstrom. Its thermal conductivity was measured to be 5.29 W mK(-1) at 300 K. Meanwhile, transmission spectra were recorded at room temperature, and then its absorption spectra were obtained combining with the transmission spectra of LuGG crystal. The transition intensity parameters Omega(t) (t = 2, 4, 6), the oscillator strengths, fluorescence branching ratios, transition probabilities and the lifetimes of Ho3+ in LuGG crystal were all evaluated by the Judd-Ofelt theory. Furthermore, its emission spectra were also determined and analyzed. (C) 2012 Elsevier B.V. All rights reserved.

The Yb,Er,Ho∶ GSGG crystal was grown successfully by the Czochralski method.Its spectroscopic characteristics were investigated.The absorption spectrum in the range of 320-3000 nm were measured.The fluorescence spectrum and lifetime were determined by exciting with 970 nm laser,the emission cross-section was calculated by F-L formula.These parameters were also compared with the Er∶ GSGG and Yb,Er∶ GSGG crystals,suggesting the new Yb,Er,Ho∶ GSGG laser crystal is more suitable to be pumped by LD laser and the 2.79 μm laser output is realized easily with low threshold and high efficiency.

Bi~(3+),Eu~(3+),Tb~(3+) doped Lu_3TaO_7 were synthesized by solid-state reaction method.The powders were characterized by XRD patterns,excitation,emission spectra and decay curves.All of Lu_3TaO_7 doped by the three kinds of ions show the considerable strong luminescence,Bi~(3+) presents a broad emission band peaking at 431 nm and the decay time is 16.8μs,Eu~(3+),Tb~(3+) show the typical sharp emission peaks of rare earth ions and the decay times are 1.26 ms and 1.20 ms,respectively.So they can be applied as potential high-density scintillators.

A Sm:GGG crystal was grown by the Czochralski method. The absorption and emission spectra of Sm:GGG were measured at room temperature. According to the Judd–Ofelt theory, the intensity parameters Ωt (t=2, 4, 6), spontaneous transition probabilities, branching ratio and radiative lifetime of 4G5/2 state were calculated. The emission cross-sections of 567, 613, 662 and 710 nm were estimated. The decay curve of the 613 nm emission assigned to the 4G5/2→6H7/2 transition was measured and the fluorescence lifetime was also determined.

M-type GdTaO4 and Tb:GdTaO4 bulk single crystals were first grown by Czochralski method. Transmission, excitation, emission spectra and luminescence decay curves of them were measured. The refractive indices of GdTaO4 were calculated with its transmission spectrum and fitted with Sellmeier equation. GdTaO4 shows Gd3+ absorption and defect luminescence, GdTaO4 exhibits its typical absorption and luminescence in GdTaO4. The luminescence decay times of GdTaO4 and Tb:GdTaO4 were also determined by fitting luminescence decay curves with single-exponential function.

The Cr/Nd GLSAG crystal were grown by Czochralski method, its structure and luminescence properties were studied, which show that the luminescence properties of Nd(3+) ions were improved by co-doping Cr(3+) ions and adjusted by mixed garnet

Eu:Gd3Sc2Ga3O12 powder was synthesized by co-precipitation method with metal Ga, Eu2O3, Gd2O3, Sc2O3 as starting materials and aqueous ammonia as precipitator. X-ray diffraction (XRD), the Rietveld refinement method and transmission electron microscope (TEM) were employed to study the crystal structure. The fluorescent spectra and decay curves were used to investigate the luminescence properties of the resulting powders. The XRD spectra and results of the Rietveld refinement indicated that the structure of Gd3Sc2Ga3O12 hardly changed and only crystal lattice distorted a little when Eu3+ ion was doped. The transmission electron microscope (TEM) observation and XRD line broadening calculation revealed that the particle size of Eu:Gd3Sc2Ga3O12 powder increased with the increase of the calcination temperature. At the same time, the emission intensity and lifetime of Eu:Gd3Sc2Ga3O12 powder also increased with the calcination temperature. In the emission spectra, a 590nm orange line from 5D0→7F1 as the most prominent group meaned that Eu3+ ion mainly occupied the inversion center in Gd3Sc2Ga3O12 crystal which may be caused by a small number of Gd atoms entered the 16(a) site.

Er3+/Yb3+:Gd3Sc2Ga3O12 and Er3+:Gd3Sc2Ga3O12 crystals have been grown by Czochralski method. The absorption spectra from 320 to 1700nm and the up-conversion fluorescence spectra from 500 to 750nm of them were investigated at room temperature, respectively. The possible up-conversion luminescence mechanisms in Er3+/Yb3+-codoped crystals and their influences on the 2.8μm laser emission were discussed. Experimental results show that the absorption of Er3+:Gd3Sc2Ga3O12 around 966nm and its bandwidth are remarkably increased by Yb3+ sensitizing. Under 940nm excitation, the up-conversion luminescence intensity of Er3+/Yb3+:Gd3Sc2Ga3O12 is much stronger than that of Er3+:Gd3Sc2Ga3O12. It demonstrates that there exist effective energy transfer processes between Yb3+ and Er3+, and the dominant mechanism of up-conversion may be the energy transfer processes of Yb3+-Er3+ and Er3+-Er3+.

Nd:YAG precursor was synthesized by a co-precipitation method with NH4HCO3 as the precipitant.The precursor and the powders sintered at different temperatures were characterized by infrared spectra(IR),X-ray diffractometry(XRD),transmitted electron microscopy(TEM),fluorescence spectral analysis etc.The intermediate phases YAP and YAM in the powder sintered at 900～1000 ℃ were detected and the reasons for the appearance of intermediate phases by co-precipitation method were analyzed.When the sintered temperature was up to 1100 ℃,pure and well-dispersed YAG phase with 40～80 nm particle size can be obtained.Additionally,spectral studies showed that Nd:YAG nano-powder had good photoluminescence.Its fluorescence and infrared spectra had no obvious difference from that of the single crystal.

The Nd-GGG crystal was grown successfully by the Czochralski method, and its structure was studied by laser Micro-Raman spectra. The Raman peaks and fluorescence peaks were discerned by using two excitation wavelengths (Ar+ 325 nm and 514.5 nm), the appeared fluorescence peaks were analyzed the tetrahedral, octahedral and dodecahedral structure of Nd:GGG crystal were contacted with the Raman peaks, and the vibration modes were also recognized. The obtained results are helpful to research the structure of solid-liquid boundary layer during the Nd:GGG growth and the change rule of the growth unit in the boundary layer.

Eu:GGG phosphors were prepared by co-precipitation method and sintered at different temperatures.The structure was analysed by X-ray diffraction and the lattice constant was calculated,which was 1.2371 nm.Emission,excitation spectra and fluorescence decay curve were measured at room temperature.There was a strong excitation band from 240 to 287 nm and a peak at 393 nm,and they were from the charge transfer absorption of Eu3+-O2-and the 7F0→5L6 transition absorption of Eu3+,respectively.The peak of 274 nm in the excitation spectrum was from the 8S7/2→6IJ transition of Gd3+.Under 393 nm excitation,the strongest emission at 591 nm was from the 5D0→7F1 magnetic dipole transition of Eu3+,maybe due to the distribution of some Eu3+ in the inverse symmetry sites.With the increasing of the sintered temperature,the fluorescent intensity increased,which might be the result of larger grain size with more excitated Eu3+ ions per unit volume.However,the fluorescence decay time at 591 nm decreased,which could be ascribed to trap capture to resonance transfer fluorescence of Eu3+ ions.

The Nd:GGG crystal was grown successfully by the Czochralski method,and its structure was studied by laser Micro-Raman spectra.The Raman peaks and fluorescence peaks were discerned by using two excitation wavelengths(Ar+ 325 nm and 514.5 nm),the appeared fluorescence peaks were analyzed the tetrahedral,octahedral and dodecahedral structure of Nd:GGG crystal were contacted with the Raman peaks,and the vibration modes were also recognized.The obtained results are helpful to research the structure of solid-liquid boundary layer during the Nd:GGG growth and the change rule of the growth unit in the boundary layer.

It has made great progress in the viscosity measurement methods recently.Some conventional methods are summarized in this paper.The new measurement methods developed recently and the viscosity measurement in crystal growth were laid an emphasis on,and also the development of viscosity measurement in crystal growth was prospected.Then the direction of the development of viscosity measurement in crystal growth was proposed.

In order to grow high-quality gallium garnet crystals, polycrystalline materials were used as starting materials. YSGG precursor was synthesized by co-precipitation method using aqueous ammonia as a precipitator, and the precursor was then sintered at different temperatures. The results showed that the feasible pH range was 8.3 ∼ 9.84 in the process of co-precipitation reaction. The YSGG precursor and the powders sintered at different temperatures were characterized by IR, XRD and TEM methods. It was found that the precursor transformed to pure YSGG polycrystalline phase at 800 °C. YSGG nano-polycrystalline powders sintered at 800 ∼ 1000 °C were well dispersed and the sizes of the YSGG grains were about 40 ∼ 100 nm.