燃烧物理学基础

新型氧氟化物玻璃的化学稳定性

对新型含碲氧氟化物玻璃在中性、碱性、酸性条件下的化学稳定性进行了研究。实验表明：水的侵蚀使玻璃表面形成碱性沉淀物．阻碍了侵蚀反应进一步发生，使在抗水实验中，质量损失并不随碲含量的增加而增加。对碱侵蚀后的样品用盐酸漂洗的实验显示，随氧化碲含量增加，玻璃化学稳定性变差；经碱腐蚀后，玻璃表面雾化，可见透过率明显减低。碱中浸泡后未用酸漂洗的样品在3100nm附近出现明显的水吸收峰；盐酸处理后，羟基吸收峰消失，但整体的中红外透过率下降。玻璃在酸性条件下侵蚀相同时间的质量损失是碱中的7倍．但由于是均匀腐蚀，侵蚀前后玻

Host dependent frequency upconversion of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses

The upconversion luminescence properties of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses under 980 nm excitation are investigated experimentally. The intense blue and relatively weak red emissions centered at 475 and 649 nm corresponding to the transitions (1)G(4) -> H-3(6) and (1)G(4) -> H-3(4) of Tm3+, respectively, are simultaneously observed at room temperature. The effect of PbF2 on upconversion intensity is observed and discussed, and possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Yb3+/Tm3+-codoped oxyfluoride tellurite glasses may be a potentially useful material for developing blue upconversion optical devices. (c) 2005 Elsevier B.V. All rights reserved.

Microstructure and laser-induced damage threshold of ZrO2 coatings dependence on annealing temperature

ZrO2 coatings were deposited on different substrates of Yb:YAG and fused silica by electron beam evaporation. After annealed for 12 h at 673 and 1073 K, respectively, weak absorption of coatings was measured by surface thermal lensing (STL) technique, and then laser-induced damage threshold (LIDT) was determined also. The crystalline phase of ZrO2 coatings and the size of the crystal grain were investigated by X-ray diffraction. It was found that microstructure of ZrO2 coatings was dependent on both annealing temperature and substrate structure, and coatings containing monoclinic phases had higher damage threshold than others. Due to the strong absorption of Yb:YAG, damage threshold of coatings on Yb:YAG was much less than that on fused silica. (C) 2004 Elsevier B.V. All rights reserved.

Laser conditioning of ZrO2 : Y2O3/SiO2 mirror coatings prepared by E-beam evaporation

Laser conditioning effects of the dielectric mirror coatings with different designs were investigated. Simple quarter-wave ZrO2:Y2O3/SiO2 mirrors and half-wave SiO2 over-coated ZrO2:Y2O3/SiO2 mirror coatings were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously. During the sub-threshold fluence raster scanning, the minor damage about defects size was found and the assumption of pre-damage mechanism, based on the functional damage concept, was put forward. The improvement of the laser induced damage threshold (LIDT) was attributed to the benign damage of the defects and the dependence on the coating design owed to the damage growth behavior of different coating designs. (C) 2004 Elsevier B.V. All rights reserved.