Er^3＋／Yb^3＋共掺的氧化镧钇透明陶瓷的光谱性能研究

采用传统无压烧结工艺制备了Er^3＋／Yb^3＋共掺的氧化镧钇透明陶瓷并对其光谱性能进行了研究．样品具有较大的吸收和发射截面．La2O3的添加使样品的荧光寿命（τs）与玻璃接近，当Yb^3＋和Er^3＋的掺杂量分别为5at％和0．5at％时，测得τs=9．65ms．这种荧光寿命长、发射截面大和线宽窄的特性有利于微型、可集成化和大功率激光输出的实现．

Far-field intensity distribution of a beam generated by a resonator with a phase-unifying mirror

The far-field intensity distribution (FFID) of a beam generated by a phase-unifying mirror resonator was investigated based on scalar diffraction theory. Attention was paid to the parameters, such as obscuration ratio and reflectivity of the phase-unifying mirror, that determine the FFID. All analyses were limited to the TEM00 fundamental mode. (c) 2005 Optical Society of America.

Optimization of near-field optical field of multi-layer dielectric gratings for pulse compressor

Multi-layer dielectric (MLD) gratings for pulse compressors in high-energy laser systems should provide high diffraction efficiency as well as high laser induced damage thresholds (LIDT). Nonuniform optical near-field distribution is one of the important factors to limit their damage resistant capabilities. Electric field distributions in the gratings and multi-layer film region are analyzed by using Fourier modal method. Optimization of peak electric field in the gratings ridge is performed with a merit function, including both diffraction efficiency and electric field enhancement when the top layer material is HfO2 and SiO2, respectively. A set of optimized gratings parameters is obtained for each structure, which reduce the peak electric field within the gratings ridge to being respective 1.39 and 1.84 times the value of incident light respectively. Finally, we also discuss the effects of gratings refractive index, gratings sidewall angle and incident angle on peak electric field in the gratings ridge. (c) 2006 Elsevier B.V. All rights reserved.

多层介质膜脉冲压缩光栅近场光学特性分析

利用傅里叶模式理论分析了TE波自准直角入射的使用条件下，多层介质膜光栅的光栅区和多层膜区电场分布的特点．分别讨论了HfO2和SiO2为顶层光栅材料时，光栅结构参数对光栅脊峰值电场的影响，结果表明，对于不同膜厚的顶层材料，存在一个最佳膜厚度，使光栅脊峰值电场最小，并且当膜厚增大时，设计大高宽比的光栅可以降低该电场峰值．最后，在大角度条件下使用多层膜光栅也可以降低光栅脊处的峰值电场．

薄膜材料对TiO2基薄膜激光损伤阈值的影响

abstract {The optical property, structure, surface properties (roughness and defect density) and laser-induced damage threshold (LIDT) of TiO₂ films deposited by electronic beam (EB) evaporation of TiO₂ (rutile), TiO₂ (anatase) and TiO₂ + Ta₂O₅ composite materials are comparatively studied. All films show the polycrystalline anatase TiO₂ structure. The loose sintering state and phase transformation during evaporating TiO₂ anatase slice lead to the high surface defect density, roughness and extinction coefficient, and low LIDT of films. The TiO₂ + Ta₂O₅ composite films have the lowest extinction coefficient and the highest LIDT among all samples investigated. Guidance of selecting materials for high LIDT laser mirrors is given.}

全内反射式衍射光栅近场光学特性

利用傅里叶模式理论分析了具有高衍射效率的全内反射式衍射光栅在TE和TM偏振态下的近场光分布特点，讨论了光栅结构参数以及入射角度对光栅内电场增强的影响。结果表明：全内反射光栅内部电场分布对偏振态较敏感，光栅槽深和占宽比对电场增强影响较小，光栅内的峰值电场随光栅周期增大而增大，并且峰值电场随着入射角度的增大而减小。在应用于高功率激光时，降低光栅内部的电场增强可以有效降低损伤风险。

多层介质膜脉冲宽度压缩光栅与超短脉冲作用时的性能分析

基于啁啾脉冲放大技术的超短脉冲激光系统是提供超快、超强激光的重要途径，具有良好输出波形和高损伤阈值的多层介质膜脉冲宽度压缩光栅是获得高峰值功率脉冲激光的关键。基于傅里叶谱变换方法和严格模式理论，分析了多层介质膜光栅（MDG）在超短脉冲作用下的光学特性。结果表明，当MDG的反射带宽小于具有高斯分布的入射脉冲的频谱宽度时，-1级反射脉冲呈非对称高斯分布，其前沿出现振荡，并且-1级反射脉冲能量开始剧烈下降，讨论了MDG结构参数对其反射带宽的影响。分析了MDG与超短脉冲作用时的近场光分布，对提高其抗激光损伤特性具

大功率微波与臭氧等复合因子对大棚蔬菜根结线虫及土壤的作

虫（nematodes）是世界农业生产的一大障碍，每年给世界农业生产造成约1000亿美元的巨额损失，是世界各国一直关注的重点病害之一。线虫可以危害各种大田作物和各种温室植物，几乎所有的栽培植物都有线虫危害发生。随着人们环保意识的增强以及健康意识的觉醒，传统防治根结线虫的药物如溴甲烷等因对环境的破坏作用，或者由于高毒、使用不便、抗药性等原因而迅速退出历史舞台，研究环保高效防治线虫成为世界各国竞相发展的技术之一。本研究尝试通过物理方式防治蔬菜根结线虫，并调查了对土壤质量的影响，主要内容包括： 1. 设计制造了功率20 Kw，频率为915 MHz的大功率土壤微波处理机，并通过了田间试验; 2. 设计制造了每小时120 g臭氧产量的便携式臭氧土壤处理机，并通过了田间试验; 3. 采用4因素3水平正交法L9(34)在山东寿光蔬菜大棚进行了蔬菜根结线虫的防治试验，综合考察微波、臭氧、微波吸收剂、EM菌等不同处理水平对根结线虫和对土壤质量的影响，结果表明： 1) 大棚土壤经微波60 s照射能够显著降低甜瓜根结线虫数和根结指数（p < 0.05），盆栽试验只需处理10 s即可显著防治甜瓜根结线虫（p < 0.01）;以120 g/h臭氧浓度处理5 s也能显著降低甜瓜根结线虫的数量（p < 0.05）;田间施入5 g/m2的EM菌，能够显著降低甜瓜根结线虫的数量（p < 0.05）;盆栽试验中微波吸收剂具有降低根结线虫数量的趋势，但是不同处理水平之间差异不显著，田间试验则具有增加根结线虫的趋势，不同处理水平之间也没有显著差异。 2) 微波不同处理水平之间对甜瓜单瓜重的影响没有显著差异;以120 g/h臭氧浓度处理甜瓜能够显著增加甜瓜单瓜重（p < 0.05）;200 g/m2微波吸收剂能够显著提高甜瓜单瓜重（p < 0.05）;以5 g/m2EM菌处理土壤则显著降低甜瓜单瓜重（p < 0.05）。 3) 微波、臭氧、微波吸收剂不同处理水平对甜瓜糖度的影响没有显著差异;以3 g/m2的EM菌处理甜瓜能够显著降低甜瓜的糖度。 4) 不同因素对甜瓜硬度的影响没有显著差异。 5) 微波处理60 s能够显著提高甜瓜的果型指数（p < 0.1），臭氧、微波吸收剂、EM菌等因素不同处理水平之间对果型指数影响差异不显著。 6) EM菌5 g/m2处理浓度能够显著降低甜瓜株高（p < 0.1），微波、臭氧、微波吸收剂不同处理水平之间对株高的影响没有显著差异。 7) EM菌5 g/m2处理浓度能够显著降低甜瓜根径（p < 0.1），微波、臭氧、微波吸收剂不同处理水平之间对根径的影响没有显著差异。 8) 微波处理60 s能够显著降低表层土壤（0-5 cm）的有机质含量（p < 0.01）;以120 g/h的臭氧浓度处理，则可以显著提高10-15 cm土壤的有机质含量（p < 0.05），其它处理因素的不同水平对有机质的影响差异不显著。 9) 微波不同处理水平对土壤全氮的影响没有显著差异（p < 0.05）;120 g/h臭氧处理浓度能够显著降低表层土壤（0-5 cm）的土壤全氮量（p < 0.1）;100 g/m2微波吸收剂处理水平能够显著提高10-15 cm土壤全氮量（p < 0.05）;EM菌3 g/m2的处理水平则显著降低5-10 cm土壤全氮量（p < 0.05）。 10) 微波、微波吸收剂、EM菌不同处理水平之间对土壤全磷没有显著影响;240 g/h臭氧浓度处理5 s能够显著降低10-15 cm土层的土壤全磷含量(p < 0.05)。 11) 微波、微波吸收剂对土壤全磷没有显著影响;臭氧处理具有降低土壤有效磷的趋势，EM菌处理则有提高土壤有效磷的趋势，但是 不同处理水平之间差异不显著（p > 0.05）。 12) 微波处理对土壤EC值没有显著影响;臭氧、微波吸收剂、EM菌处理具有降低土壤EC值的趋势，但是不同处理水平之间差异不显著（p > 0.05）。 13) 微波处理30 s能够显著降低表层土壤的pH值（p < 0.05），臭氧、微波吸收剂、EM菌处理具有提高土壤pH值的趋势，但是不同处理水平之间差异不显著。

Solid source MBE growth of quantum cascade lasers

High material quality is the basis of quantum cascade lasers (QCLs). Here we report the solid source molecular beam epitaxy (MBE) growth details of realizing high quality of InGaAs/InAlAs QCL structures. Accurate control of material compositions, layer thickness, doping profile, and interface smoothness can be realized by optimizing the growth conditions. Double crystal x-ray diffraction discloses that our grown QCL structures possess excellent periodicity and sharp interfaces. High quality laser wafers are grown in a single epitaxial run. Room temperature continuous-wave (cw) operation of QCLs is demonstrated.

Controlled growth of III-V compound semiconductor nano-structures and their application in quantum-devices

This paper reviews our work on controlled growth of self-assembled semiconductor nanostructures, and their application in light-emission devices. High-power, long-life quantum dots (QD) lasers emitting at similar to 1 mu m, red-emitting QD lasers, and long-wavelength QD lasers on GaAs substrates have successfully been achieved by optimizing the growth conditions of QDs.

Defects around self-organized InAs quantum dots measured by slow positron beam

Self-organized InAs quantum dots (QDs) have been fabricated by molecular beam epitaxy. The authors try to use a slow positron beam to detect defects in and around self-organized QDs, and point defects are observed in GaAs cap layer above QDs. For the self-organized InAs QDs without strain-reducing layer, it is free of defects. However, by introducing a strain-reducing layer, the density of point defects around larger sized InAs QDs increased. The above results suggest that low energy positron beam measurements may be a good approach to detect depth profiles of defects in QD materials. (c) 2007 American Institute of Physics.

Effect of oxidation on the optical and surface properties of AlGaN

The chemical properties of AlxGa1-xN surfaces exposed to air for different time periods are investigated by atomic force microscopy (AFM), photoluminescence (PL) measurement and X-ray photoelectron spectroscopy (XPS). PL and AFM results show that AlxGa1-xN samples exhibit different surface characteristics for different air-exposure times and Al contents. The XPS spectra of the Al 2p and Ga 2p core levels indicate that the peaks shifted slightly, from an Al-N to an Al-O bond and from a Ga-N to a Ga-O bond. All of these results show that the epilayer surface contains a large amount of Ga and Al oxides. (c) 2006 Elsevier B.V. All rights reserved.

Studies of 6H-SiC devices

Silicon carbide (SiC) is recently receiving increased attention due to its unique electrical and thermal properties. It has been regarded as the most appropriate semiconductor material for high power, high frequency, high temperature, and radiation hard microelectronic devices. The fabrication processes and characterization of basic device on 6H-SiC were systematically studied. The main works are summarized as follows:The homoepitaxial growth on the commercially available single-crystal 6H-SiC wafers was performed in a modified gas source molecular beam epitaxy system. The mesa structured p(+)n junction diodes on the material were fabricated and characterized. The diodes showed a high breakdown voltage of 800 V at room temperature. They operated with good rectification characteristics from room temperature to 673 K.Using thermal evaporation, Ti/6H-SiC Schottky barrier diodes were fabricated. They showed good rectification characteristics from room temperature to 473 K. Using neon implantation to form the edge termination, the breakdown voltage was improved to be 800 V.n-Type 6H-SiC MOS capacitors were fabricated and characterized. Under the same growing conditions, the quality of polysilicon gate capacitors was better than Al. In addition, SiC MOS capacitors had good tolerance to gamma rays. (C) 2002 Published by Elsevier Science B.V.

A novel application to quantum dot materials to the active region of superluminescent diodes

We have proposed a new superluminescent diodes (SLD) aimed at wide spectrum-quantum dot superluminescent diodes (QD-SLD), which is characterized by the introduction of a self-assembled asymmetric quantum dot pairs active region into conventional SLID structure. We investigated the structure and optical properties of a bilayer sample with different InAs deposition amounts in the first and second layer. We find that the structure of a self-assembled asymmetric quantum dot pairs can operate up to a 150 nm spectral width. In addition, as the first QDs' density can modulate the density of the QDs on the second layer, due to relatively high QDs density of the first layer, we can get the strong PL intensity from a broad range. We think that for the broad spectral width and the strong PL intensity, this structure can be a promising candidate for QW-SLD. (C) 2002 Elsevier Science B.V. All rights reserved.

A New Technique for Side Pumping of Double-Clad Fiber Lasers

We report a new technique, called SAP, for side pumping of double-clad, rare-earth-doped fiber lasers using fiber-coupled pump sources. The highest coupling efficiency can even exceed 92% in theory with this structure.