KNSBN晶体猫式互抽动相位共轭光特性

在KNSBN：Ce晶体中，利用二波耦合作用，在单一光束无法获得相位共轭光的条件下，实现了“猫”式互抽运相位共轭光输出，获得较高的共轭光发射率，实验结果表明，晶体的二波耦合作用可以使晶体的自抽运相位共轭光的阈值光强降低。入射光的入射角范围增大，响应时间缩短。     

Raman spectroscopic study of ceramic Sr2Bi4Ti5O18

Raman spectra of ceramic Sr2Bi4Ti5O18 （SBTi5） are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material＇s structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum （FWHM）, which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one.     

二维非正交坐标斜方格金属光子带隙结构

金属光子带隙结构在高能加速器、微波真空电子器件和太赫兹波源等方面具有重要的应用前景.基于实空间传输矩阵理论，详细研究了非正交坐标系下二维斜方格金属光子带隙结构，给出了计算横电模、横磁模完全带隙结构的一般公式，并分析了填充系数、任意斜角及金属柱横截面对带隙结构的影响.计算结果在退化为正方格情况下时，与其他方法的计算结果取得很好的一致. 关键词： 光子晶体 金属光子带隙 传输矩阵法 微波真空电子器件     

Converged properties of clean metal surfaces by all-electron first-principles calculations

All-electron full-potential linearized augmented plane-wave calculations of the surface energy, work function, and interlayer spacings of close-packed metal surfaces are presented, in particular, for the free-electron-like metal surfaces, Mg(0 0 0 1) and Al(1 1 1), and for the transition metal surfaces, Ti(0 0 0 1), Cu(1 1 1), Pd(1 1 1), and Pt(1 1 1). We investigate the convergence of the surface energy as a function of the number of layers in the slab, using the Cu(1 1 1) surface as an example. The results show that the surface energy, as obtained using total energies of the slab and bulk from separate calculations, converges well with respect to the number of layers in the slab. Obviously, it is necessary that bulk and surface calculations are performed with the same high accuracy. Furthermore, we discuss the performance of the local-density and generalized gradient approximations for the exchange-correlation functional in describing the various surface properties.     

High longitudinal selectivity of shifting multiplexing in volume holograms

High longitudinal selectivity of the shifting multiplexing with spherical reference wave is proposed and demonstrated. A simplified method based on wave optics is used for calculating the selectivity, and the result fits well the experimental measurement. Under the paraxial condition, a simple formula for the longitudinal selectivity is introduced. With use of an object lens with effective NA=0.817, we obtain that an FWHM of selectivity is as small as 1 μm.     

晶体学与准晶体学点群的母子群关系

依据群论，得出了准晶体学点群的直积或半直积推导算式；依据结晶学理论，绘出了五角、八角、十角和十二角晶系各点群的极赤投影图.据此推导出了每一个准晶体学点群的全部最大子群，从而推导并绘制出了三维晶体学和准晶体学点群之间的母子群关系(60个点群的“家谱”).该“家谱”以最大子群链的图解形式直观地给出了每个点群的最小母群和最大子群. 关键词： 准晶体 晶体 点群 最大子群 最小母群 群链     

Nd∶NaR(WO_4)_2晶体生长(R=Bi,Y)

采用提拉法生长出了掺钕钨酸铋钠[Nd∶NaBi(WO4)2,简称Nd∶NBW]和掺钕钨酸钇钠[Nd∶NaY(WO4)2,简称Nd∶NYW]晶体,并给出了制备无开裂优质Nd∶NBW和Nd∶NYW晶体的最佳生长工艺参数。从XRD分析得到Nd∶NBW和Nd∶NYW晶体的晶胞参数,并分析了晶体的拉曼光谱,认为二者结构基本相同,为四方晶系、白钨矿结构、I41/a空间群。由吸收光谱可以看出,Nd∶NBW在802nm有较强的吸收峰,Nd∶NYW在804nm、752nm、586nm附近有较强、较宽的吸收峰,二者均适合于LD泵浦;计算了晶体中Nd3+的吸收截面积。     

Density functional theory investigation of the structure of SO2 and SO3 on Cu(1 1 1) and Ni(1 1 1)

Density functional theory (DFT) slab calculations, mainly using the generalised gradient approximation, have been used to investigate the minimum energy structures of molecular SO₂ and SO₃ on Cu(1 1 1) and Ni(1 1 1) surfaces. On Ni(1 1 1) the optimal local adsorption structures are in close agreement with experimental results for both molecular species obtained using the X-ray standing wavefield technique, although for adsorbed SO₂ the energetic difference between two alternative lateral positions of the lying-down molecule on the surface is marginally significant. On Cu(1 1 1) the results for adsorbed SO₂, in particular, were sensitive to the DFT functional used in the calculations, but in all cases failed to reproduce the experimentally-established preference for adsorption with the molecular plane perpendicular to the surface. This result is discussed in the context of previously published DFT results for these species adsorbed on Cu(1 0 0). The optimal geometry found for SO₃ on Cu(1 1 1) is similar to that on Ni(1 1 1), providing agreement with experiment regarding the molecular orientation but not the adsorption site.     

多层光子晶体滤波器研究

从双层结构出发研究了一种由多块不同的单周期光子晶体组合而成的多层结构的滤波器，论述了这种滤波器的工作原理，研究表明这种结构适于制作带通、窄带通过、带阻、宽带带阻、高通以及其它各种性能的滤波器。实验和理论研究的结果相一致。     

Nd:LuVO_4晶体的拉曼光谱研究

采用不同的几何配置测量了Nd:LuVO4晶体的室温拉曼光谱,根据群论对称性分类计算了该晶体的红外和拉曼活性振动模并与实验结果做了比较,指认了测定的特征谱线。测量并分析了Nd:LuVO4晶体A1g全对称类的高温拉曼光谱,讨论了拉曼频移随温度变化的关系,认为晶体的热膨胀是引起拉曼频移变化的主要原因。