Microstructure of the crystals generated in borate glass irradiated by femtosecond laser pulses

In this study, we examined the microstructure of crystals generated in borate glass by femtosecond laser irradiation (FSLI). The distribution of the high-temperature and low-temperature phases of barium metaborate crystals produced in the borate glass is analyzed using Raman spectroscopy. We then propose the possible mechanism for the generation of crystals in glass by FSLI.

Structural investigation on TeO2-BiCl3 glassy system

Glass systems of composition xBiCl(3)-(1-x)TeO2 (x=0.2, 0.4, 0.5 and 0.6, respectively) have been investigated by means of DSC, infrared absorption spectroscopy and Raman spectroscopy in order to obtain information about the transformation of structure, thermal and optical properties in the formation of the glass network. The results confirm that the addition of BiCl3 network former increases the glass forming ability and the optical transmission range. And also from Raman results a structural evolution was observed where the number of structural units described as [TeO3] trigonal pyramids, [TeO3+1] polyhedra and ionic behavior bonds (NBO) increases at the expense of the [TeO4] trigonal bipyramids. Bi3+ ions exist in network structure as [BiO6] or [BiCl6] octahedral coordination. As upconversion luminescence glass host, this glassy system is desired for optical properties but the thermal stability will still be improved. (c) 2005 Elsevier B.V. All rights reserved.

beam-shaping microstructure optical fiber

Microstructure optical fiber with uniform intensity distribution of the fundamental mode is proposed. The design guide line and characteristics of this kind fiber are demonstrated. The relationship between refractive index profile and structure parameters is investigated. The mechanism of forming uniform fundamental mode in these fibers is analyzed.

Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago

The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We review the terrestrial Late Cretaceous record from Europe and discuss its importance for understanding the paleogeography, ecology, evolution, and extinction of land-dwelling vertebrates. We review the major Late Cretaceous faunas from Austria, Hungary, France, Spain, Portugal, and Romania, as well as more fragmentary records from elsewhere in Europe. We discuss the paleogeographic background and history of assembly of these faunas, and argue that they are comprised of an endemic 'core' supplemented with various immigration waves. These faunas lived on an island archipelago, and we describe how this insular setting led to ecological peculiarities such as low diversity, a preponderance of primitive taxa, and marked changes in morphology (particularly body size dwarfing). We conclude by discussing the importance of the European record in understanding the end-Cretaceous extinction and show that there is no clear evidence that dinosaurs or other groups were undergoing long-term declines in Europe prior to the bolide impact.

Effect of La2O3 on microstructure and transmittance of transparent alumina ceramics

Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H-2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities (T. D.) with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at a wavelength range of 300 - 800 nm.

Nd：YAG透明陶瓷的烧成及其显微结构

由溶胶一凝胶／燃烧合成结合法合成了Nd：YAG(掺钕钇铝石榴石，neodymium—doped yttrium aluminium garnet)粉体，用真空烧结法制备了Nd：YAG透明陶瓷。研究了显微结构随烧结温度和保温时间的变化，并对透明陶瓷的晶界结构和成分分布进行了表征。随着烧结温度的提高和保温时间的延长，Nd：YAG陶瓷的密度增大，晶形发育完整，透过率提高。晶粒内部和晶界的化学组成基本相同。所制备的Nd：YAG透明陶瓷在激光工作波长1064nm的透过率达到75％。

沉积参量及时效时间对SiO2薄膜残余应力的影响

SiO2薄膜由电子束蒸发方法沉积而成。用GPI数字波面光学干涉仪测量了不同沉积条件下玻璃基底镀膜前后曲率半径的变化，并确定了SiO2薄膜中的残余应力。在其他条件相同的情况下，当沉积温度由190℃升高到350℃时，SiO2薄膜中的压应力由一156MPa增大为-289MPa。氧分压由3．0×10^-3Pa升高到13．0×10^-3Pa时，SiO2薄膜中的应力由-223．5MPa变为20．4MPa。通过对薄膜折射率的测量，发现薄膜的堆积密度随沉积条件的改变也发生了规律性的变化。应力的变化主要是由于沉积时蒸发粒子

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.

Effect of microstructure of TiO2 thin films on optical band gap energy

TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4 eV to 3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.

氧分压对电子束蒸发SiO2薄膜机械性质和光学性质的影响

采用ZYGO MarkⅢ-GPI数字波面干涉仪、NamoScopeⅢa型原子力显微镜对不同氧分压下电子束蒸发方法制备的SiO2薄膜中的残余应力及表面形貌进行了研究，结果发现：随着氧分压的增大，薄膜中的压应力值逐渐减小，最后变为张应力状态；同时薄膜的表面粗糙度也随着氧分压的增大而逐渐增大，另外，折射率对氧分压也非常敏感，随着氧分压的增大呈现出了减小的趋势，这些现象主要是由于氧分压的改变使得SiO2薄膜结构发生了变化引起的。