Temperature dependence of femtosecond laser induced refractive index change in Nd3+-doped phosphate glass

We report refractive index change in a femtosecond laser irradiated Nd3+-doped phosphate glass. The effects of annealing temperature on the refractive index change of the glass have been investigated. Absorption spectra of the glass sample before and after femtosecond laser irradiation and subsequent annealing were measured. The results indicate that multiphoton absorption can undertake although there are intrinsic absorption for the glass in irradiation wavelength. The results may be useful for fabrication of three-dimensional integrated optics devices and waveguide laser devices in this glass. (c) 2004 Elsevier B.V. All rights reserved.

Investigation of optical properties of Ce3+-doped Gd2SiO5 crystal irradiated by a femtosecond laser

We report on the optical property changes for Ce3+-doped Gd2SiO5 crystal irradiated by a femtosecond (fs) laser. Absorption spectra showed that Ce-related color centers were formed in this crystal after an 800 nm fs laser irradiation. The annealing temperature-dependence of the refractive index and absorption intensity changes have been investigated. Furthermore, a new way of writing overlapped gratings inside the crystal by use of birefringence of fs laser beam in this crystal was proposed. (c) 2005 Elsevier B.V. All rights reserved.

钛宝石中子辐照色心的研究

研究了中子辐照下钛宝石单晶体缺陷的形成及光学性能的变化。对温度梯度法(TGT)生长的钛宝石晶体进行中子辐照。中子能量为1．5MeV，剂量为4．32×10^18 neutrons／cm^2。辐照后194nm吸收峰强度增加,268nm吸收峰强度则降低。荧光谱检测中发现辐照使得420nm荧光峰强度明显降低，荧光峰位置也蓝移至414nm处。分析表明辐照使得钛宝石晶体内形成F^+缺陷，同时Ti^4+离子则转化成Ti^3+离子。辐照后的钛宝石在247C处有热释光TL出现，通过初始上升法计算出其陷阱深度为0．63eV。

蓝宝石中子辐照色心的研究

研究了中子辐照对蓝宝石(α-Al2O3)单晶体缺陷形成及光学性能的影响，对采用提拉法与温度梯度法生长的蓝宝石晶体进行中子辐照，通过对比辐照前后的吸收及荧光光谱变化，发现辐照使得蓝宝石晶体内形成F、F^+和F2^+色心缺陷，但不同方法生长的晶体样品中色心浓度差异明显。其中提拉法样品的F心浓度要高于温度梯度法样品，而温度梯度法样品中F^+色心浓度要高于提拉法样品。分析表明，这与两种方法生长的晶体中杂质含量差异有关。通过研究辐照后晶体的热致发光谱发现提拉法与温度梯度法生长的蓝宝石晶体分别在145℃与150℃有明

Defects in U3+: CaF2 single crystals grown under different conditions by the temperature gradient technique

Defects in as-grown U3+ : CaF2 crystals grown with or without PbF2 as an oxygen scavenger were studied using Raman spectra, thermoluminescence glow curves, and additional absorption (AA) spectra induced by heating and gamma-irradiation. The effects of heating and irradiation on as-grown U3+: CaF2 crystals are similar, accompanied by the elimination of H-type centers and production of F-type centers. U3+ is demonstrated to act as an electron donor in the CaF2 lattice, which is oxidized to the tetravalent form by thermal activation or gamma-irradiation. In the absence of PbF(2)as an oxygen scavenger, the as-grown U3+:CaF2 crystals contain many more lattice defects in terms of both quantity and type, due to the presence of O2- impurities. Some of these defects can recombine with each other in the process of heating and gamma-irradiation. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of gamma irradiation and air annealing on Yb-doped YAlO3 single crystals

The effects of gamma irradiation on as-grown 5 at% Yb:YAlO3 (YAP) and air annealing on gamma-irradiated 5 at% Yb: YAP have been studied by the difference in the absorption spectra before and after treatment. The gamma irradiation and air annealing led to opposite changes of the absorption properties of the Yb: YAP crystal. After air annealing, the gamma-irradiation effects were totally removed over the wavelength range 390-800 nm and the concentrations of Fe3+ and Yb3+ were slightly increased. For the first time, the gamma-irradiation-induced valence changes between Yb3+ and Yb2+ ions in Yb: YAP crystals have been observed. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of air annealing on the spectral properties of Ce : Y3Al5O12 single crystals grown by the temperature gradient technique

Five absorption hands, at 227, 300 340, 370 and 457nm, were observed in the optical absorption spectrum of Ce:Y3Al5O12 (Ce:YAG) crystals grown by the temperature gradient technique (TGT). The absorption bands at 227, 340, and 457 nm were identified Lis belonging to the Ce3+ -ion in the YAG crystal. A near UV optical emission band at 398nm was observed. with an excitation spectrum containing two bands, at 235 and 370nm. No fluorescence was detected under 300 nm excitation. The pair of absorption bands at 235 and 370 nm and the absorption band at 300 nm were attributed to the F- and F+-type color centers, respectively. The color centers model was also applied to explain the spectral changes in the Ce:YAG (TGT) crystal, including the reduction in the Ce 31 -ion absorption intensity, after annealing in an oxidizing atmosphere (air). (C) 2004 Elsevier B.V. All rights reserved.

V^3＋：YAG晶体的生长、色心与光谱性能研究

采用石墨电阻加热的温梯法生长了V：YAG晶体，晶体的不同部位呈现两种不同的颜色：浅绿色和黄褐色．通过对比分析不同颜色V：YAG晶体的室温吸收光谱，推断出石墨发热体高温下扩散出来的C可以起到还原作用，提高晶体中V^3＋tetra离子的浓度，同时诱导了F心的形成．在1300℃下，对不同颜色的V：YAG晶体进行真空退火处理，发现处于八面体格位中的V^3＋离子在热激发作用下与近邻的四面体格位Al^3＋离子存在置换反应，由此产生一定浓度的四面体格位V^3＋离子．同时，F心在退火过程中被完全消除，释放出来的自由电子被

Characteristics and optical spectra of V : YAG crystal grown in reducing atmosphere

A V:YAG single crystal was grown by the temperature gradient technique (TGT) with graphite-heating elements. The as-grown crystal has different colorations of light green and yellow brown in different parts. Distribution of vanadium in three samples with different colorations was determined by inductively coupled plasma-mass spectrometry. From the absorption spectrum of the yellow-brown part with peaks at 370, 820 and 1320nm, we can deduce that the reducing atmosphere of carbon diffused from the heating elements can increase the concentration of tetrahedral V3+ ions and induce F color centers. All three samples exhibited light-green color after annealing in vacuum or H-2 atmospheres. In the vacuum annealing process, the V3+ ions in tetrahedral positions were enhanced through two methods: one method is the exchanging of octahedral V3+ and tetrahedral Al3+ ions in neighboring sites under thermal excitation, the other is that F color centers were thoroughly eliminated and the escaped free electrons could be captured by V ions with higher valance states to further improve the concentration of tetrahedral V3+ ions. Besides the two mechanisms, the H-2 annealing process greatly improved the V-tetra(3+) ions through the reduction effect of H-2. (c) 2006 Elsevier B.V. All rights reserved.

Effect of annealing and gamma irradiation on undoped and Eu3+-doped Y2SiO5 single crystals

The absorption spectra of the undoped Y2SiO5 and Eu3+-doped Y2SiO5 crystals grown by the Czochralski technique were compared before and after annealing and, similarly, the unannealed and annealed crystals after gamma-ray irradiation. The absorption bands of Eu2+ ions with peaks at 300 and 390 nm were observed in the as-grown Y2SiO5:Eu3+ crystal. These peaks were more intense in H-2-annealed and irradiated Y2SiO5:Eu3+ crystals. The additional absorption peaks at 260 and 320-330 nm which were attributed to F color centers and O- hole centers were observed in irradiated undoped Y2SiO5 and Y2SiO5:Eu3+ crystals, respectively. (c) 2005 Elsevier B.V. All rights reserved.

飞秒激光辐照K9玻璃引起的暗化和折射率变化

对不同辐照条件下近红外飞秒激光在K9玻璃内部诱导产生的暗化现象和永久性折射率改变进行了实验研究。通过辐照前后的显微镜图片、吸收光谱、电子自旋共振谱(ESR)以及激光衍射实验，分析了K9玻璃中暗化现象产生的微观过程，发现暗化是由诱导产生的空穴型色心引起的。暗化程度和折射率改变随激光强度、扫描速度、扫描行间距变化而变化。光致色心的形成与非线性电离有关。对折射率永久性改变进行了简单说明，其机理仍在探索中。

Effect of gamma-irradiation on spectral properties of undoped Y2SiO5 crystals

The absorption spectra of undoped Y2SiO5 crystals were studied before and after gamma-irradiation. After gamma-irradiation, the additional absorption peaks at 260-270 and 320nm were observed in as-grown and H,annealed Y2SiO5 crystal, but it did not occur in air-annealed Y2SiO5 crystal. These absorption peaks were attributed to F color centers and O- hole centers, respectively. Owing to more oxygen vacancies and color centers in H-2-annealed Y2SiO5 crystal than that in as-grown Y2SiO5 crystal after gamma-irradiation, the additional absorption peaks were more intense in the former than that in the latter. With the irradiation dose increasing from 20 to 220kGy, the intensity of additional absorption peaks increased.

近红外超快强激光在LiF晶体内空间选择性诱导产生色心

通过显微镜聚焦近红外超快强激光作用在垂直于激光束移动的LiF晶体样品上，在LiF晶体中连续地诱导产生色心。以一定的间隔．反复移动该激光束的焦斑可在LiF晶体内空间选择性地诱导产生稳定的色心区。测定了不同条件下形成的色心区的吸收光谱，结果表明用近红外超快强激光可在LiF晶体中诱导产生具有激光效应的色心。

Effects of gamma-irradiation and air annealing on Yb-doped Y3Al5O12 single crystal

The effects of gamma-irradiation on the air-annealed 10 at.% Yb:Y3Al5O12 (YAG) and air annealing on the gamma-irradiated 10at.% Yb:YAG have been studied by the difference absorption spectra before and after treatment. The gamma-irradiation and air annealing led to opposite changes of the absorption properties of the Yb:YAG crystal. After air annealing, the gamma-irradiation induced centers were totally removed and the concentration of Fe3+ and Yb3+ were lightly increased. For the first time, the gamma-irradiation induced valence changes between Yb3+ and Yb2+ ions in Yb:YAG crystals have been observed. (C) 2007 Elsevier B.V. All rights reserved.

First-principles study of the electronic structures and absorption spectra for the PbMoO4 crystal with lead vacancy

The electronic structures and absorption spectra for the perfect PbMoO4 crystal and the crystal containing lead vacancy V-Pb(2-) with lattice structure optimized are calculated using density functional theory code CASTEP. The calculated absorption spectra of the PbMoO4 crystal containing V-Pb(2-) exhibit three absorption bands peaking at 2.0 eV (620 nm), 3.0 eV (413 run) and 3.3 eV (375 nm), which are in good agreement with experimental values. The theory predicts that the 390 nm, 430 nm and 580 run absorption bands are related to the existence of V-Pb(2-) in the PbMoO4 crystal.