Upconversion emission of a Er3+-doped glass microsphere under 633 nm excitation (vol 35, pg 353, 2004)

　

Upconversion emission of a Er3+-doped glass microsphere under 633 nm excitation

In this work, The TBS glass microspheres doped with Er3+ for morphology-dependent resonances of upconversion emission were designed. The glass sample components are 25TiO(2)-27BaCO(3)-8Ba(NO3)(2)-6ZnO(2)-9CaCO(3)-5H(3)BO(3)-10SiO(2)-7water glass-3Er(2)O(3) (wt%), and the emission spectra of TBS glass and a TBS glass microsphere (about 48 mum in diameter) were measured under 633 nm excitation and discussed. The strong morphology-dependent resonances of upconversion luminescences in the microsphere were observed. The observed resonances could be assigned by using the well-known Lorenz-Mie Formalism. (C) 2003 Elsevier Ltd. All rights reserved.

Upconversion emission of a Er3+-doped glass microsphere under 633 nm excitation

In this work, The TBS glass microspheres doped with Er3+ for morphology-dependent resonances of upconversion emission were designed. The glass sample components are 25TiO(2)-27BaCO(3)-8Ba(NO3)(2)-6ZnO(2)-9CaCO(3)-5H(3)BO(3)-10SiO(2)-7water glass-3Er(2)O(3) (wt%), and the emission spectra of TBS glass and a TBS glass microsphere (about 48 mum in diameter) were measured under 633 nm excitation and discussed. The strong morphology-dependent resonances of upconversion luminescences in the microsphere were observed. The observed resonances could be assigned by using the well-known Lorenz-Mie Formalism. (C) 2003 Elsevier Ltd. All rights reserved.

具有单元分裂功能的间断有限元方法

介绍一种能够模拟材料开裂过程的有限元方法,该方法引入单元分裂和界面分离技术,结合具体的破坏准则,模拟材料变形中的破坏,同时还可以方便地处理材料中任意分布的界面结构.以三点弯曲实验为例,通过数值模拟结果和实验数据的比较,验证了该方法的适用性.

Squeeze-film Effects in MEMS Devices with Perforated Plates for Small Amplitude Vibration

Squeeze-film effects of perforated plates for small amplitude vibration are analyzed through modified Reynolds equation (MRE). The analytical analysis reckons in most important influential factors: compressibility of the air, border effects, and the resistance caused by vertical air flow passing through perforated holes. It is found that consideration of air compressibility is necessary for high operating frequency and small ratio of the plate width to the attenuation length. The analytical results presented in this paper agree with ANSYS simulation results better than that under the air incompressibility assumption. The analytical analysis can be used to estimate the squeeze-film effects causing damping and stiffness added to the system. Since the value of Reynolds number involved in this paper is low (< 1), inertial effects are neglected.

充液腔体旋转运动的稳定性理论

本文对于具有一个定点,并充满粘性液体的腔,在重力场中绕惯性主轴的平衡旋转运动,采用Movchan直接法,就尽可能多样的Movchan距离,推广了和的稳定性定理,并对尽可能全面的腔参数(包括临界情况在内)给出了具体的稳定性结论。

双套管密相气力输运过程的数值模拟和能耗分析

基于计算流体力学理论,提出一种可用于预测双套管密相气力输送系统能耗的新方法.与以往依靠经验的计算方法不同,本工作将输送管道分为起始段与充分发展段两部分,分别进行详细的计算流体力学模拟后汇总得出整个系统的总能耗.压力梯度为750 Pa/m的情况下,计算所得物料输送速率为10 t/h,耗气量为290 m~3/h,实验所得物料输送速率为8.0 t/h,耗气量240 m~3/h,证明本数模方法是可靠的.

Ce：Mn：LiNbO3晶体紫外记录研究

采用紫外光作记录光在Ce：Mn：LiNbO3晶体中实现非挥发全息记录，灵敏度可达0．0803cm／J，衍射效率（固定）为5．07％，比采用红光为记录光，紫外光为敏化光的非挥发双中心记录方案均提高了50多倍。分析表明，采用紫外光作为记录光，深能级电子被激发比例极大提高，参与光折变过程的电子平均运动周期变短．提高了衍射效率和灵敏度；深浅能级电子光栅的同相位，使得固定空间电荷场变强。文中还研究了退火对记录性能的影响。

LiNbO3∶Fe∶Rh晶体近红外非挥发全息记录

采用双中心记录方案在双掺杂LiNbO3∶Fe∶Rh晶体中实现了近红外非挥发全息记录,研究了LiNbO3∶Fe∶Rh晶体在633 nm,752 nm,799 nm波长下的全息记录性能。结果表明,在使用近红外记录光时,其记录灵敏度随敏化光强的变化趋势与双中心短波长记录时的不同。通过和LiNbO3∶Fe∶Mn等传统双掺杂铌酸锂晶体的近红外波段记录效果对比,发现同时掺杂Fe和Rh可增强晶体对近红外光的吸收,获得更高的浅中心Fe光生伏特系数,从而能够在LiNbO3∶Fe∶Rh晶体中实现近红外波段的光折变全息记录。

Absorption characteristic and nonvolatile holographic recording in LiNbO3 : Cr : Cu crystals

The absorption characteristic of lithium niobate crystals doped with chromium and copper (Cr and Cu) is investigated. We find that there are two apparent absorption bands for LiNbO3:Cr:Cu crystal doped with 0.14 wt.% Cr2O3 and 0.011 wt.% CuO; one is around 480 nm, and the other is around 660 nm. With a decrease in the doping composition of Cr and an increase in the doping composition of Cu, no apparent absorption band in the shorter wavelength range exists. The higher the doping level of Cr, the larger the absorbance around 660 nm. Although a 633 nm red light is located in the absorption band around 660 nm, the absorption at 633 nm does not help the photorefractive process; i.e., unlike other doubly doped crystals, for example, LiNbO3:Fe:Mn crystal, a nonvolatile holographic recording can be realized by a 633 nm red light as the recording light and a 390 nm UV light as the sensitizing light. For LiNbO3:Cr:Cu crystals, by changing the recording light from a 633 nm red light to a 514 nm green light, sensitizing with a 390 nm UV light and a 488 nm blue light, respectively, a nonvolatile holographic recording can be realized. Doping the appropriate Cr (for example, N-Cr = 2.795 X 10(25)m(-3) and N-Cr/N-Cu = 1) benefits the improvement of holographic recording properties. (c) 2005 Optical Society of America.

Effect of wavelength of sensitizing light on holographic storage properties in LiNbO3 : Fe : Ni crystal

By sensitizing with 514 nm green light, 488 nm blue light and 390 nm ultraviolet light, respectively, recording with 633 nm red light, effect of wavelength of sensitizing light on holographic storage properties in LiNbO3:Fe:Ni crystal is investigated in detail. It is shown that by shortening the wavelength of sensitizing light gradually, nonvolatile holographic recording properties of oxidized LiNbO3:Fe:Ni crystal is optimized gradually, 390 nm ultraviolet light is the best as the sensitizing light. Considering the absorption of sensitizing light, to obtain the best performance in two-center holographic recording we must choose a sensitizing wavelength that is long enough to prevent unwanted absorptions (band-to-band, etc.) and short enough to result in efficient sensitization from the deep traps. So in practice a trade-off is always needed. Explanation is presented theoretically. (c) 2005 Elsevier GmbH. All rights reserved.

双中心全息记录的矢量分析与记录方向优化

对描述双掺杂晶体非挥发性全息记录动力学过程的Kukhtarev方程进行了矢量分析, 分析中考虑了体光生伏特效应和外加电场的作用。在小信号近似的基础上给出了双中心全息记录中记录与固定阶段空间电荷场的矢量解析解。在综合考虑空间电荷场的各向异性以及晶体有效电光系数的各向异性后, 给出了双中心全息记录的优化记录方向。结果表明, 对(Fe, Mn):LiNbO3晶体633 nm寻常光记录, 优化记录方向主要由有效电光系数决定, 光栅波矢与光轴夹角为22°, 方位角为30°;对(Fe, Mn):LiNbO3晶体633

Study of near-infrared nonvolatile two-center holographic recording in LiNbO3:Fe:Rh crystal

The near-infrared nonvolatile holographic recording has been realized in a doubly doped LiNbO3:Fe:Rh crystal by the traditional two-center holographic recording scheme, for the first time. The recording performance of this crystal has been investigated by recording with 633 nm red light, 752 nm red light and 799 nm near-infrared light and sensitizing with 405 nm purple light. The experimental results show that, co-doped with Fe and Rh, the near-infrared absorption and the photovoltaic coefficient of shallow trap Fe are enhanced in this LiNbO3:Fe:Rh crystal, compared with other doubly doped LiNbO3 crystals Such as LiNbO3:Fe:Mn. It is also found that the sensitizing light intensity affects the near-infrared recording sensitivity in a different way than two-center holographic recording with shorter wavelength, and the origin of experimental results is analyzed. (C) 2007 Elsevier GrnbH. All rights reserved.

Gain characteristics of Er3+-doped phosphate glass fibres

An erbium-doped phosphate glass fibre has been drawn by the rod-in-tube technique in our laboratory. The gain for the Er3+-doped phosphate glass fibre with different pump powers and with different input signal wavelengths is investigated. The 2.2-cm-long fibre, pumped by a single-mode 980-nm fibre-pigtailed laser diode, can provide a net gain per unit length greater than 1.8dB/cm. The pump threshold is about 50 mW at the wavelength of 1534 nm, and below 70 mW at 1550 nm. The gain linewidth of the Er3+-doped phosphate glass fibre is greater than 34 nm and can cover the C band in optical communication networks.