First-principles study of the optical properties of PbTiO<Subscript>3</Subscript>

The optical properties of PbTiO₃ were studied from first principles using the density functional theory. The dielectric functions and optical constants are calculated using the full potential–linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). The theoretical calculated optical properties and energy loss (EEL) spectrum yield a static refractive index of 2.83 and a plasmon energy of 23.1 eV for cubic phase. The effective electron number at low energy saturates near 20 eV with the value of 18.1 for the effective electron number. In the tetragonal phase the static refractive index decreases to 2.59 and yields a plasmon energy of 22.7 eV.     

电子辐照对掺铒单模光纤损耗特性的影响

本文介绍了掺铒(Er³⁺)单模光纤电子辐照特性,测量了辐照前后和退火后的光纤参数。发现在0.80-1.60μm范围内辐照引起的损耗很大,在0.80-1.20μm短波部分辐照损耗遵循L_UV=0.342exp[E/0.166];而1.20-1.60μm长波部分遵循L_IR=2.2·10⁴exp[-6.08E](E的单位为eV)。120℃退火60h可使长波辐照损耗减少,但0.80μm附近的损耗反而增加。最后讨论了辐照损耗的机理 关键词：     

Infrared and optical spectroscopy of alpha- and gamma-phase cerium

We determined the optical properties of alpha- and gamma-phase Ce in the photon energy range from 60 meV to 2.5 eV using ellipsometry and grazing incidence reflectometry. We observe significant changes of the optical conductivity, the dynamical scattering rate, and the effective mass between alpha- and gamma-cerium. The alpha-phase is characterized by a Fermi-liquid frequency-dependent scattering rate, and an effective mass of about 20m(e) on an energy scale of about 0.2 eV. In gamma-Ce the charge carriers have a large scattering rate in the far infrared and a carrier mass characteristic of 5d band electrons. In addition, we observe a prominent absorption feature in alpha-Ce, which is absent in gamma-Ce.     

Influence of the core‐hole effect on optical properties of magnesium oxide (MgO) near the Mg L‐edge region

The influence of the core‐hole effect on optical properties of magnesium oxide (MgO) is established through experimental determination of optical constants and first‐principles density functional theory studies. Optical constants (δ and β) of MgO thin film are measured in the spectral region 40–300 eV using reflectance spectroscopy techniques at the Indus‐1 synchrotron radiation source. The obtained optical constants show strong core exciton features near the Mg L‐edge region, causing significant mismatch with Henke's tabulated values. On comparing the experimentally obtained optical constants with Henke's tabulated values, an edge shift of ～3.0 eV is also observed. Distinct evidence of effects of core exciton on optical constants (δ and β) in the near Mg L‐edge absorption spectra are confirmed through first‐principles simulations.     

Optical Properties of Semiconducting Ruthenium Silicide

The optical properties of ruthenium silicide Ru₂Si₃ have been studied theoretically and experimentally. The energy band spectrum and optical properties were simulated with the aid of the firstprinciple selfconsistent method of linear attached plane waves. The spectral dependence of the absorption coefficient in the 0.52.2 eV energy range was measured experimentally by the photothermal refractive spectroscopy method. It is established that ruthenium silicide is a directgap semiconductor having an energy gap of 0.84 eV and a low oscillator strength of the first direct transition.     

有机非线性晶体二苯甲酮光学性质的实验研究

首次从实验上研究了过冷熔体法生长的有机非线性晶体二苯甲酮的光学特性，采用最小偏向角法和干涉法测量了晶体的主折射率，确定了该晶体的负光性双轴结构并求出了光轴夹角，测量了晶体在近紫外到近红外波段的光谱透射率，结果表明，由过冷熔体法生长的有机非线性晶体二苯甲酮在近紫上到近红外波段具有均匀且较高的透射特性．     

有机非线性晶体二苯甲酮光学性质的实验研究

首次从实验上研究了过冷熔体法生长的有机非线性晶体二苯甲酮的光学特性,采用最小偏向角法和干涉法测量了晶体的主折射率,确定了该晶体的负光性双轴结构并求出了光轴夹角,测量了晶体在近紫外到近红外波段的光谱透射率,结果表明,由过冷熔体法生长的有机非线性晶体二苯甲酮在近紫上到近红外波段具有均匀且较高的透射特性。     

镧掺杂BaSnO3薄膜的电学和光学特性

利用射频磁控溅射法在(LaAlO₃)_0.3(SrAl_0.5Ta_0.5O₃)_0.7 (001)单晶基底上生长了镧掺杂BaSnO₃外延薄膜. 通过Hall效应和热电势测量证实了镧掺杂BaSnO₃薄膜具有n型简并半导体特征, 并且基于载流子浓度和Seebeck系数计算出电子的有效质量为0.31m₀ (m₀为自由电子质量). 镧掺杂BaSnO₃薄膜在可见波段具有良好的透明性(透过率大于73%). 基于介电模型对薄膜的透过率曲线进行拟合, 从拟合结果中不仅得到了薄膜的厚度为781.2 nm, 能带宽度为3.43 eV、 带尾宽度为0.27 eV和复光学介电常数随波长的变化规律, 而且也强力地支持了基于电学参数计算电子有效质量的正确性.     

六方氮化硼单层中一种(CN)3VB缺陷的第一性原理计算

二维六方氮化硼(hBN)的点缺陷最近被发现可以实现室温下的单光子发射,而成为近年的研究热点.尽管其具有重要的基础和应用研究意义,hBN中发光缺陷的原子结构起源仍然存在争议.本文采用基于密度泛函理论的第一性原理计算,研究hBN单层中一种B空位附近3个N原子被C替代的缺陷(CN)3VB.在hBN的B空位处,3个N原子各自带一个在平面内的悬挂键及相应的未配对电子,而通过C替换可以消除未配对的电子.系统研究了(CN)3VB缺陷的几何结构、电子结构以及光学性质,结果表明,缺陷可以由一个对称的亚稳态经过原子结构弛豫变成1个非对称的、3个C原子连在一起的基态结构.缺陷的形成在hBN中引入了一些由缺陷悬挂σ键及重构的π键贡献的局域缺陷态.这些缺陷态可以导致能量阈值在2.58 eV附近的可见光内部跃迁.本文的工作有助于进一步理解hBN中点缺陷的构成及光学性质,为实验上探讨发光点缺陷的原子结构起源及其性质提供理论依据.     

Excitation of triplet <Emphasis Type="Italic">D</Emphasis> levels of barium atoms in collisions with electrons

The excitation of triplet D levels of the barium atom by slow electrons, which gives rise to optical emission due to spontaneous transitions from these levels, is experimentally studied. 85 excitation cross sections are measures at an exciting electron energy of 30 eV. 16 optical excitation functions are recorded within the electron energy range of 0–200 eV. The results obtained for seven transitions are compared with previously published experimental data.