Directional scattering and self-pumped phase conjugation in photorefractive crystal

The directional scattering in photorefractive SBN crystal is reported.The self-pumped phase conjugation has been realized with the feedback of this directional scattering andthe performance parameters are compared with those of cat self-pumped phase conjugator.     

Anomalous changes in CuO2 plane in YBa2Cu4O8 under pressure

We report the results of an atomistic simulation study of the pressure-induced structural changes in YBa₂Cu₄O₈ from 0 to 20 GPa. It is found that the crystal has similar compressibilities in the a- and b-directions over the whole pressure range, whereas in the c-direction there are quite different compressibilities at different pressures. Our results suggest that there exists a correlation between the charge transfer and the change in the Cu(2)---O(1) bond length, but we do not support the suggestion of a direct dependence of T_c on the length of this bond. However, we predict that there are anomalous changes in the CuO₂ plane with pressure, which we propose may lead to a charge carrier redistribution on in-plane copper and in-plane oxygens, which in turn may be related to the optimum carrier concentration in the CuO₂ plane.     

硬脂酸晶体压力效应的FT-IR光谱研究

 本文在0~4 GPa范围内研究了预压力对硬脂酸晶体的相关场劈裂和固态-熔融态相变过程的影响。通过γCH₂面内摇摆振动模和γ'CH₂相关场模的强度和频率变化,发现预压力对晶体内的相关场合分子链取向有明显的影响。预压力对硬脂酸的熔点虽然没有影响,但对γ'CH₂模有“硬化”作用。并且由此出发,对硬脂酸的预熔过程作了讨论。     

分布反馈光纤激光器的研制

利用相位掩膜板,直接在掺饵光纤上紫外写入π／２相位光栅,研制出１０ｃｍ长相移分布反馈（ＤＦＢ）光纤激光器,并对其调制特性进行了研究。     

Superheating of confined Pb thin films

In this work we report, for the first time, an experimental observation of a superheating phenomenon in metal thin films. By means of cold rolling, Pb thin films of about 20 nm thick were sandwiched by Al layers, and between them semicoherent epitaxial Pb/Al interfaces were formed. In situ x-ray diffraction analysis indicated that the confined Pb thin films could be superheated for at least 6 degrees C. Thermodynamic analysis indicated that such a substantial superheating in the confined two-dimensional thin films may originate from suppression of growth of the molten droplets by the epitaxial Al/Pb/Al confinement, instead of suppression of melt nucleation for the confined particle superheating.     

半无限规划与方向导数

本文对半无限凸规划提出一个用方向导数表述的对偶问题，其对偶间隙为零．     

Influence of NH beam bombarding energy on structural characterization and cell attachment of CNx coating

The carbon nitride (CN_x) coating with its novel properties will be excellent candidate for biomedical applications. CN_x coatings were prepared on the surface of Ti–6Al–4V by ion-beam-assisted deposition (IBAD) with different NHⁿ⁺ beam bombarding energies at low substrate temperature. The coatings were characterized by Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The result showed that the wear-resistance of CN_x coatings was better at higher beam bombarding energy. The cell attachment tests also gave interesting results that CN_x coatings exhibited low macrophage attachment and provide desirable surface for the normal cellular growth and morphology of the fibroblasts. Structural analysis showed that NHⁿ⁺ beam bombardment at the energies of 300–400 eV could result in more nitrogen concentration and fraction of sp³CN bonds in the structure of CN_x coatings, which may be responsible for the improvement in the wear-resistance and the cell attachment.     

STABILITY OF BRIGHT SCREENING-PHOTOVOLTAIC SPATIAL SOLITONS

We present a theoretical analysis of the stability of screening-photovoltaic (SP) spatial solitons in biased photovoltaic-photorefractive materials in the case of neglecting the loss of the material and the effect of diffusion. When an incident optical beam is a SP soliton, this beam propagates along a linear path with its shape kept unchanged. When the maximum amplitude, width and functional form of an incident optical beam are slightly different from those of a SP soliton, the beam reshapes itself and tries to evolve into a solitary wave after a short distance. That is, these SP solitons are stable against small perturbations. However, optical beams that significantly differ from SP soliton solutions tend to experience larger cycles of compression and expansion, and their maximum amplitudes oscillate with propagation distances. The larger the perturbations, the stronger the oscillation.     

静水压对立方钙钛矿CsSnX3(X=I, Br, Cl)光电性质的第一性原理探究

全无机无铅卤化物钙钛矿已经成为重要的新一代太阳能电池材料.采用密度泛函理论的第一性原理研究了不同静水压下CsSnX₃(X=I, Br, Cl)材料的晶体结构,电子结构和光学性能,并分析了其内在联系.结果表明施加静水压可使材料中Sn-X键长减小,使原子之间的耦合增强,带隙值减小,且随着卤族元素半径的增大,压力效应越明显;随着压力的增加,材料的吸收系数和复折射率增大,吸收光谱出现红移现象,在可见光区和近红外光区吸收增强.相比CsSnBr₃和CsSnCl₃,CsSnI₃在可见光区吸收最佳且受压力作用影响最小,更适用于钙钛矿太阳能电池材料.