Growth and spectroscopic characteristics of Nd-doped PbWO4 crystal

Nd-doped PbWO4 crystals are grown by using the modified Bridgman method.The spectroscopic properties of the crystals are investigated.The changes of the absorption band at 350 nm are discussed for samples annealed at 740℃ and 1040℃.The radiative lifetime of the 4 F 3/2 level is calculated by using the Judd-Ofelt theory according to the absorption spectrum of 0.5 at.% Nd-doped PbWO 4 crystal.The spontaneous Raman scattering properties of the crystals are analysed.     

Comparison of spectroscopic properties of Yb:YAP and YbiYAG crystals

The Yb:YAG and Yb:YAP crystals have been grown by Czochralski method. The absorption spectra and the fluorescence spectra of Yb:YAG and Yb:YAP crystals have been investigated. It is shown that the Yb:YAG crystal has better laser properties and smaller threshold power than Yb:YAP crystal. In addition, the absorption cross-section of the Yb:YAP crystal is 2.16 times of that of the Yb:YAG crystal, so laser diode pumped Yb:YAG lasing can be easily realized. Because YAP single crystal is anisotropic, it is provided with polarization characteristics.     

复合结构激光陶瓷研究进展

多晶激光陶瓷相比单晶激光材料而言,具有可实现大尺寸制备的优势,并可通过结构和功能复合为固体激光器的设计提供最大的可能性和灵活性.复合结构激光陶瓷的制备方法除了采用传统的单晶键合工艺之外,还可以结合陶瓷近净尺寸成型和烧结过程的特点,从而极大地丰富了复合结构激光增益介质的可实现形式.本文综述了复合结构激光陶瓷的典型制备方法,并论述了几类复合结构激光陶瓷的应用与进展,并对复合结构激光陶瓷发展中的问题和发展方向进行了论述.     

Intensities and spectral features of the ~4I_(13/2)-~4I_(15/2) potential laser transition of Er~(3+) centers in CaF_2-CeF_3 disordered crystal

A CaF_2-CeF_3 disordered crystal containing 1.06% of Er~(3+) ions was grown by the temperature gradient technique.Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the ~4I_(13/2)→~4I_(15/2) transition of Er~(3+). In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the ~4I_(13/2) emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of 0.73 × 10~(-20) cm~2, and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature ~4I_(13/2)→~4I_(15/2) emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb~(3+) ions in heavily doped CaF_2 erbium ions in the CaF_2-CeF_3 crystal reside in numerous sites with dissimilar relaxation rates.     

非结构化环境下机器人视觉导航的路径识别方法

提出了一种基于模糊粗糙集的非结构化路径识别与机器人引导方法。通过自适应面阵列电荷耦合传感器的图像清晰度控制方法,获取了最佳信息量图像。构建了模糊粗糙集的非结构化路径识别模型,借助粗糙集理论预定义图像目标、背景和不确定区域,融合相对模糊连接度竞争机制对不确定区域的像素进行了模糊重分类,精确描绘了机器人的导航路径。该模型可实现未知非结构化路径区域的自动识别,亦可引入灰度先验特征识别指定路径区域。结果表明,该方法对提高机器人在非结构化环境中的自主探索能力具有实际意义。     

Efficient multi-wavelength lasers made of Nd:GdLuAG crystal

Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd:Gd Lu AG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ～80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.     

(Sm1-xAlx)2Ce2O7化合物的热物理性能

以Al2O3、Sm2O3和CeO2为原材料,采用固相反应法制备了(Sm1-xAlx)2Ce2O7化合物.对其相结构,显微组织和热物理性能进行了研究.结果表明,合成的(Sm1-xAlx)2Ce2O7化合物具有单一的萤石型晶格,该化合物致密度均在90;以上,晶粒界面明显.三价铝离子的引入能明显降低其导热性能,热膨胀性能虽虽然有所降低,但高温热膨胀系数大于YSZ,满足热障涂层的要求.     

高平均功率固态激光器的实验研究

高平均功率固态激光器在先进制造业和激光武器等领域有重要应用。本文从激光工作物质激活离子的选择、基质的不同对激光器性能的影响等方面来进行研究,得到Yb:LuAG晶体是一种应用于高平均功率激光器中更具潜力的增益介质的结论。通过该研究,学生在掌握了激光器相关知识的基础上,培养了科研能力和创新思维。     

V-doped MgAl6O10:novel luminescence substrate for phosphor-free UV-white LEDs

V-doped MgAl6O10 is grown by the conventional Czochralski method. The crystal structure and the cell parameters are analyzed through X-ray diffraction experiments. The absorption and emission spectra are investigated. Under pumping at 324 nm, the emission spectra of V-doped MgAl6O10 obtain two emission peaks at the wavelengths of 471 and 570 nm. Two emission bands of the spectra combine to produce a spectrum that is perceived as white by the naked eye. Therefore, V-doped MgAl6O10 single crystal can be applied as substrate for phosphor-free ultraviolet (UV)-white light-emitting diodes (LEDs).