纳米尺寸的ZnO晶体高压相变的拉曼散射研究(英文)

Weperformedthehigh-pressureRaman measurementofthethreenanosizedZnOcrystals. Wefoundthesmallerthesize,thehigherthe pressuretoinducethephasetransitionfrom w櫣rzitetorock-saltstructure. High-pressureRamanmeasurementsof nona-shapedZnOcrystalswerepreformed.The…     

Optically tunable chromatic dispersion controller with coupled-cavity etalon structure

We propose and demonstrate a novel optically tunable dynamic dispersion-compensation device with coupled-cavity etalon structure. Experimentally, it was achieved with an all-fiber coupled-cavity etalon made in an Er/Yb codoped fiber pumped by a 980-nm laser diode. The dispersion was tuned from -300 to +400 ps/nm in the experiment. The potential advantages of such optically tunable dispersion compensators include fast response time and remotely controllable operation.     

Potential PDP phosphors with strong absorption around 172 nm: Rare earth doped NaLaP2O7 and NaGdP2O7

NaLaP₂O₇ and NaGdP₂O₇ powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln³⁺ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln³⁺ ions in both hosts show analogous luminescence. For Ce³⁺-doped samples, the five Ce³⁺ 5d levels can be clearly identified. As for Pr³⁺ and Tb³⁺-doped samples, strong 4f-5d absorption band around 172 nm is observed, which matches well with Xe-He excimer in plasma display panel (PDP) devices. As a result, Pr³⁺ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb³⁺-doped NaREP₂O₇(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm³⁺ and Eu³⁺-doped samples, the Tm³⁺-O²⁻ charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu³⁺ is observed at abnormally low energy position, which might originate from multi-position of Eu³⁺ ions. The similarity in luminescence properties of Ln³⁺ in both hosts indicates certain structural resemblance of coordination environment of Ln³⁺ in the two sodium rare earth diphosphates.     

Restrictions on negative energy density for the Dirac field in flat spacetime

This paper investigates the quantum Dirac field in n+1-dimensional flat spacetime and derives a lower bound in the form of quantum inequality on the energy density averaged against spacetime sampling functions. The state-independent quantum inequality derived in the present paper is similar to the temporal quantum energy inequality and it is stronger for massive field than for massless one. It also presents the concrete results of the quantum inequality in 2 and 4-dimensional spacetimes.     

发展中的我国中学物理"四个类型实验"

分析总结了半个世纪来我国中学物理教学“4个类型实验”的历史、内涵、功能和教法。     

Six‐wave mixing induced by free‐carrier plasma in silicon nanowire waveguides

Nonlinear wave mixing in mesoscopic silicon structures is a fundamental nonlinear process with broad impact and applications. Silicon nanowire waveguides, in particular, have large third‐order Kerr nonlinearity, enabling salient and abundant four‐wave‐mixing dynamics and functionalities. Besides the Kerr effect, in silicon waveguides two‐photon absorption generates high free‐carrier densities, with corresponding fifth‐order nonlinearity in the forms of free‐carrier dispersion and free‐carrier absorption. However, whether these fifth‐order free‐carrier nonlinear effects can lead to six‐wave‐mixing dynamics still remains an open question until now. Here we report the demonstration of free‐carrier‐induced six‐wave mixing in silicon nanowires. Unique features, including inverse detuning dependence of six‐wave‐mixing efficiency and its higher sensitivity to pump power, are originally observed and verified by analytical prediction and numerical modeling. Additionally, asymmetric sideband generation is observed for different laser detunings, resulting from the phase‐sensitive interactions between free‐carrier six‐wave‐mixing and Kerr four‐wave‐mixing dynamics. These discoveries provide a new path for nonlinear multi‐wave interactions in nanoscale platforms.

     

混合型间隔层对荧磷混合式白色有机电致发光器件性能的影响

制备了基于新型蓝绿色荧光MQAB与红色磷光Ir(MDQ)2acac的荧磷混合式白色有机电致发光器件,并探讨了TPBI或UGH3两种间隔层及二者的混合间隔层的器件的发光性能.研究发现,采用TPBI和UGH3的混合间隔层可以调控载流子注入与传输的平衡.当m(TPBI)∶ m(UGH3)=1∶1时,可有效地控制发光区域,使得器件性能得到优化,并获得发光亮度高达14 700 cd/m2的白色有机电致发光器件,最高电流效率可达11.60 cd/A,且器件具有较高的色稳定性.采用混合间隔层的器件比单用TPBI或UGH3作为间隔层的器件效率提高了200％ ～ 300％.     

不同临界保留因子下天然有机物亲疏水组分光谱特性

吸附树脂层析法是表征环境水样有机物亲疏水组分分布的常用方法。作为柱层析的基本参数,临界保留因子对亲疏水物质的吸附及分离效果具有潜在影响。以河北某水库的水样为例,将有机物分为亲水物(HIS)、疏水酸(HOB)、疏水碱(HOA)和疏水中性物(HON),考察了在不同临界保留因子分离条件下(k′_cr=5, 10, 25, 50, 100)亲疏水组分有机物含量分布,并着重考察了其光谱学特性。研究发现,亲疏水组分的浓度分布取决于k′_cr值的设置,疏水组分的比例和疏水程度随k′_cr的增大而增大。在250~280 nm波长范围内,亲水组分HIS的紫外吸光度随k′_cr的增高而增高,而疏水组分HOA和HOB则呈现相反趋势,亲水与疏水组分之间的紫外光谱差异性随k′_cr增大而增大。此外,疏水组分单位质量浓度的吸光度对k′_cr的取值敏感,推测k′_cr可能影响所得组分的芳香族官能团性质。进一步考察了各组分的三维荧光光谱,并采用荧光区域积分和荧光指数对图谱进行解析。结果表明,亲疏水组分的荧光峰形态、荧光区域分布和荧光团密度与k′_cr值有关,荧光指数BIX,HIX_em和Peak T/C对k′_cr的取值敏感,说明k′_cr可能对所得组分的具体化学组成乃至迁移转化行为产生影响。因此在分离并表征环境水样的亲疏水组分分布时,应特别注意临界保留因子的设置并明确标明其取值。     

Gravitational Waves,baryon asymmetry of the universe and electric dipole moment in the CP-violating NMSSM

In this work, we make the first study of electroweak baryogenesis(EWBG) based on the LHC data in the CP-violating next-to-minimal supersymmetric model(NMSSM) where a strongly first order electroweak phase transition(EWPT) is obtained in the general complex Higgs potential. With representative benchmark points which pass the current LEP and LHC constraints, we demonstrate the structure of EWPT for those points and how a strongly first order EWPT is obtained in the complex NMSSM where the resulting gravitational wave production properties are found to be within the reaches of future space-based interferometers like BBO and Ultimate-DECIGO. We further calculate the generated baryon asymmetries where the CP violating sources are(1): higgsino-singlino dominated,(2): higgsino-gaugino dominated or(3): from both sources. It is shown that all three representing scenarios could evade the strong constraints set by various electric dipole moments(EDM) searches where cancellations among the EDM contributions occur at the tree level(higgsino-singlino dominated) or loop level(higgsino-gaugino dominated).The 125 GeV SM like Higgs can be either the second lightest neutral Higgs H_2 or the third lightest neutral Higgs H_3. Finally, we comment on the future direct and indirect probe of CPV in the Higgs sector from the collider and EDM experiments.     

Coherent beam combination of adaptive fiber laser array with tilt-tip and phase-locking control

We present an experimental study on tilt-tip(TT) and phase-locking(PL) control in a coherent beam combination(CBC) system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics collimator(AFOC),and the PL control is realized by the phase modulator(PM).Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent(SPGD) algorithm are investigated in this paper.Two-fiber-laser-,four-fiber-laser-,and six-fiber-laser-arrays are employed to study the TT and PL control.In the cascaded control system,only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller.In a simultaneous control system one high-speed CMOS camera and one photonic detector(PD) are employed,and a computer and a control circuit based on field programmable gate array(FPGA) are used as the controllers.Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective.Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly.The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other,so the control effect is limited.