Yin Shaotang

Luminescence and Thermal Properties of Er:GSGG and Yb,Er:GSGG Laser Crystals

Er3+-doped and Yb3+/Er3+ co-doped Gd3Sc2Ga3O12 (abbreviated as Er:GSGG and Yb,Er:GSGG, respectively) laser crystals are investigated by using a combination of spectroscopic measurements and thermal characterizations. An absorption peak of Yb, Er: GSGG crystal shifts to 970 nm and its absorption band broadens obviously, which makes the crystal suitable for pumping by a 970 nm laser diode (LD). This crystal also exhibits a shorter lifetime of a lower laser level, a larger emission cross section and higher thermal conductivity than those of Er: GSGG. All these factors suggest that Yb3+/Er3+ co-doping has a positive effect on improving the spectroscopic and thermal performances in GSGG based laser crystals, and imply that double-doped Yb, Er: GSGG crystal is a potential candidate as an excellent LD pumped 2.79 mu m laser material.

High temperature Raman spectroscopic study of the micro-structure of a caesium triborate crystal and its liquid

Raman spectra of a caesium triborate (CBO) crystal at different temperatures up to the melting temperature have been recorded. All of the peaks of corresponding to the crystal broaden and decrease in wavenumber with increasing temperature. The vibrational modes of the CBO crystal, in which the basic structural unit is the triborate group (B3O7)5−, have been simulated using a plane-wave pseudopotential method. An isomerization reaction from four-coordinated boron to a three-coordinated species was observed during the melting process. The continuous three-dimensional network of the crystal collapsed and transformed into spiral chains that consist of (B3O6)3−groups during the melting process. Detailed spectral analysis is also competently explained by applying quantum chemistry ab initio calculations.

Raman Spectrum Analysis on the Solid–Liquid Boundary Layer of BGO Crystal Growth

We study the Raman spectra of Bi4Ge3O12 crystal at different temperatures, as well as its melt. The structure characters of the single crystal, melt and growth solid–liquid boundary layer of BGO are investigated by their high-temperature Raman spectra for the first time. The rule of structure change of BGO crystal with increasing temperature is analysed. The results show that there exists [GeO4] polyhedral structure and Bi ion independently in BGO melt. The bridge bonds Bi–O–Bi and Bi–O–Ge appear in the crystal and at the boundary layer, but disappear in the melt. The structure of the growth solid–liquid boundary layer is similar to that of BGO crystal. In the melt, the long-range order structure of the crystal disappears. The thickness of the growth solid–liquid boundary layer of BGO crystal is about 50 μm.

Diode-Pumped Quasi-Three-Level Passively Q-Switched Nd:GGG Laser with a Codoped Nd,Cr:YAG Saturable Absorber

We demonstrate the first quasi-three-level passively Q-switched Nd:GGG laser at 937 nm using a Nd,Cr:YAG crystal as the saturable absorber. The dependences of the average output power, the repetition rate and the pulse width on the incident pump power are obtained. A maximum average output power of 1.18 W with repetition rate of 35 kHz and pulse width of 45 ns is achieved at an incident pump power of 18.3 W. The corresponding optical-to-optical and slope efficiencies are 6% and 10%, respectively.

Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd:YAG and Yb:YAG Laser Crystals

We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+:Y3A15O12 (Nd:YAG) and Yb3+:Y3A15O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340 nm. The former is contributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100Mrad gamma-ray In contrast, the same dose irradiation does not impair the fluorescent properties of Yb:YAG crystal. These results indicate that Yb:YAG crystal possesses the advantage over Nd:YAG crystal that has better reliability for applications in harsh radiant environment.

Structural analysis and crystal-field calculations of Nd3+ in GdxLu1−xTaO4 (x = 0.85) polycrystalline

The crystal structural parameters of Nd3+-doped rare earth orthotantalate GdxLu1?xTaO4 (x = 0.85) are determined by applying the Rietveld refinement to its X-ray diffraction, and its emission and excitation spectra at 77 K are analysed. The relativistic model of ab initio self-consistent DV-X? method, which is applied to the cluster NdO8 in GdxLu1?xTaO4, and the effective Hamiltonian model are used to investigate its spin?orbit and crystal-field parameters. The free-ions and crystal-field parameters are fitted to the experimental energy levels at 77 K with a root-mean-square deviation of 14.92 cm?1. According to the crystal-field calculations, 96 levels of Nd3+ are assigned. Finally, the fitting results of free-ions and crystal-field parameters are compared with those already reported for Nd3+:YAlO3. The results indicate that the free-ion parameters are similar to those of the Nd3+ in GdxLu1?xTaO4 and YAlO3 hosts, and the crystal-field interaction of Nd3+ in GdxLu1?xTaO4 is stronger than that in YAlO3.

Study on Thermal Expansion of Nd3+: Gd3Ga5O12 Laser Crystal

Abstract Nd 3+ :Gd 3 Ga 5 O 12 (Nd:GGG) crystals were grown by the MF induction heating Czochraski technique. Samples of Φ 3 mm × 10 mm were cut from the boule along and direction, respectively. Their thermal expansions were measured with DIL402C thermal dilatometer. Results showed that the thermal expansion coefficient of Nd: GGG single crystal varied along with temperature. The higher the temperature, the bigger the thermal expansion coefficient. At the same temperature range, the thermal expansion ratio of different samples along the same direction was equal and that of different direction samples was little different. It was discovered that the thermal expansion ratio changed linearly in the range of 150 ∼ 1100 °C. Nonlinear variation appeared in the range of 25 ∼ 150°C.

Preparation and Characterization of Y3Sc2Ga3O12 Nano-Polycrystalline Powders by Co-Precipitation Method

Abstract 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.

Temperature-dependent Raman spectroscopic study of bismuth borate Bi2ZnOB2O6

A temperature-dependent Raman spectroscopic study on Bi2ZnOB2O6 crystal was carried out to investigate the structure change of the crystal with the increase of temperature. Raman spectra of crystal Bi2ZnOB2O6 were recorded in the spectral range 10–1600 cm−1 at room temperature first. Compared with the vibrational spectra of the referred compounds, satisfactory assignment of most of the high-energy modes to vibrations of Bi–O, B–O, and Zn–O bonds was achieved. In particular, the Raman high-frequency peak located at 1344 cm–1 was attributed to the B–O vibration in the BO3 triangle. This temperature-dependent Raman spectroscopic study was carried out up to 600 °C. It was found that all the Raman lines exhibit decreases in frequency and the widths of the Raman peaks increase with increasing temperature. No phase transition was observed under 600 °C.

Growth, Structure and Transmission Spectrum of A New Type GYSGG(Gd

采用提拉法成功生长出高质量的GYSGG(Gd 0.63 Y 2.37 Sc 2 Ga 3 O 12 )晶体, 对其结构及透过光谱进行了研究。GYSGG晶体的晶格常数大于目前常用的GGG 和CaMgZr:GGG,介于YSGG与GSGG之间。可通过改变晶体中Gd与Y的比例, 获得应用中所需不同晶格常数的晶体基片。另外, 晶体三个结晶面的摇摆曲线有对称的形状和较小的半高宽, 表明晶体有较好的结晶完整性。观察分析了晶体三个结晶面的位错腐蚀图。透过光谱分析表明晶体有宽的透光波段, 将计算得到的折射率曲线拟合得到了折射率塞米尔方程系数。因此, GYSGG不仅是一种优良的激光基质晶体, 也是一种宽波段窗口材料和潜在的具有较大晶格常数, 并且晶格常数可调的新型磁泡应用衬底材料。