Localized-Surface-Plasmon Enhanced the 357 nm Forward Emission from ZnMgO Films Capped by Pt Nanoparticles

The Pt nanoparticles (NPs), which posses the wider tunable localized-surface-plasmon (LSP) energy varying from deep ultraviolet to visible region depending on their morphology, were prepared by annealing Pt thin films with different initial mass-thicknesses. A sixfold enhancement of the 357 nm forward emission of ZnMgO was observed after capping with Pt NPs, which is due to the resonance coupling between the LSP of Pt NPs and the band-gap emission of ZnMgO. The other factors affecting the ultraviolet emission of ZnMgO, such as emission from Pt itself and light multi-scattering at the interface, were also discussed. These results indicate that Pt NPs can be used to enhance the ultraviolet emission through the LSP coupling for various wide band-gap semiconductors.

临界点附近气体热传导与粘度的特性和计算方法

应用限定立方模型参数标度状态方程和重整化群理论的一些结果,提出了奇异热传导和奇异粘度的计算公式与计算方法。该方法对热传导和粘度的工程计算具有足够好的正确度,同时又非常简便,从而具有很大的实用价值。对CO_2的计算结果与测量值之间的一致性是令人满意的。它们之间的偏差小于10％。

波浪和波载

<正> 波浪是海水的基本运动形态,是海岸设施、近海结构和海上船舰所遇到的基本海况。因此波浪研究具有重要的理论和实际意义。 大体上说,波浪研究可以分为两个阶段。从19世纪中叶到本世纪50年代为第一阶段。在此期间主要运用流体动力学理论处理波浪,目的是用数学工具描述波浪的基本运动学特性。于是发展了各种确定性波浪理论(包括线性和非线性理论),求出基本方程

岩石破裂滑动过程及其声发射数值模拟

运用岩石破裂与失稳过程分析RFPA2D系统 ,对滑动形成过程进行了数值模拟研究。滑动岩体似为非均匀弹 -脆岩石材料 ,模拟结果再现了滑动形成从变形到破坏直至失稳的全过程及其声发射规律。结果表明 ,剪断面是滑动形成的主要形式 ,并首先在试样一端出现 ,然后再形成由一端及里的剪断面扩展直至另一端最后产生剪断面破坏贯通 ,形成统一的滑动面

可压衰减湍流中被动标量场的直接数值模拟及谱分析

运用高精度迎风差分方法及8阶精度群速度控制型差分格式(GVC8)对初始 Reynolds数为72，初始湍流Mach数0．2-43．9的可压衰减湍流的流场及被动标量场进行了直接数值模拟，被动标量场的Schmidt数为2~10．通过不同计算网格及不同方法的数值计算对本文结果进行了验证．指出了可压衰减湍流中被动标量能谱存在的一1律，压缩性效应使得高波数成分衰减加快．对被动标量场进行了标度律分析，发现可压湍流中被动标量场具有扩展自相似性，而压缩性效应对被动标量标度指数的影响较小．发现随着被动标量Schmidt数增加，其标度指数的奇异性增强．

Adiabatic shear localization: occurrence, theories, and applications

Wavefront measurement of double-clad pulsed ytterbium fiber laser

Because of high efficiencies, compact structure, and excellent heat dissipation, high-power fiber lasers are extremely useful for applications such as cutting, welding, precision drilling, trimming, sensing, optical transmitter, material processing, micromachining, and so on. However, the wavefront of the double clad fiber laser doped with ytterbium is still unknown. In this paper, wavefront of a fiber laser is measured and the traditional Hartmann-shack wavefront sensing method is adopted. We measured a double clad fiber laser doped with ytterbium which produces pulse wave output at infrared wavelength. The wavefront shape and contour are reconstructed and the result shows that wavefront is slightly focused and not an ideal plane wavefront. Wavefront measurement of fiber laser will be useful to improving the lasers' performance and developing the coherent technique for its applications.

Prism coupling of ultrashort light pulses into waveguides

We discuss coupling of ultrashort light pulses into waveguides by use of a prism waveguide coupler configuration. Theoretical analysis indicates that an extra loss induced by the short coherence times of ultrashort pulses, which has a strong effect on the reflected light and the optimum coupling condition, appears in the waveguide. Numerical simulations show that the reflectance strongly depends on the coherence times of ultrashort pulses. A method for realizing optimum coupling by compensating for the extra loss is proposed as well in this paper. A preliminary experiment of employing ultrashort pulses with different coherence times was carried out, and good agreement between theory and experiment was obtained. (c) 2006 Optical Society of America.

混合碱效应对磷酸盐包边玻璃性质的影响

高功率大尺寸激光玻璃硬包边技术对于提高激光玻璃的饱和增益系数具有非常重要的价值。本文采用传统的玻璃熔制方法，研究了Li-Na混合碱效应对磷酸盐包边玻璃折射率、热膨胀系数α、玻璃转变温度Tg、膨胀软化温度Td以及溶解速率（DR）的影响规律。研究结果表明：当Li/(Li+Na)=0.5时，Tg、Td和DR取得极小值，表明混合碱效应既能降低包边玻璃的转变温度，又能提高包边玻璃的化学稳定性，这些性质对于包边玻璃的设计是非常可贵的。

Structural and upconversion fluorescence properties of Er3+/Yb3+-codoped oxychloride lead-germanium-bismuth glass

Structural and infrared-to-visible upconversion fluorescence properties of Er3+/Yb3+-codoped oxychloride lead-germanium-bismuth glass have been studied. The Raman spectrum investigation indicates that PbCl2 plays an important role in the formation of glass network, and has an important influence on the upconversion luminescence owing to lower phonon energy. Intense green and red emissions centered at 525, 546, and 657 nm, corresponding to the transitions H-2(11/2)-->I-4(15/2,) I-4(3/2)-->I-4(15/2), and F-4(9/2)-->I-4(15/2), respectively, were observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation. (C) 2004 Elsevier Ltd. All rights reserved.

Encircled energy measurement for focusing lens based on scanning Hartmann test

The encircled energy of a focusing lens is one of the parameters directly affecting the target efficiency in high-power laser facilities. The direct measurement method of the encircled energy for the focusing lens based on the scanning Hartmann test is proposed in this paper. With the scanning Hartmann test setup, the information in the whole aperture of the focusing lens can be achieved. The encircled energy can be obtained by analyzing the spot diagram on the focal plane of the focusing lens. In experiments, the encircled energy of an aspheric focusing lens is measured using this method. The measurement result is in good agreement with that derived from measurement data by an interferometer and the difference is 7.7%. (C) 2006 Elsevier GmbH. All rights reserved.