Nonclassicality and Decoherence of the Variable Arcsine State in a Thermal Environment

A kind of non-Gaussian state—variable arcsine state is studied by using the input-output theories which relate the statistical properties of the output field to those of the input field. The variable arcsine state (VAS) is generated by using a variable beam splitter (BS), which means that the transmissivity (reflectivity) of the BS is adjustable continuously. The nonclassicality is investigated by studying the negativity of Wigner function (WF). It is shown that the variable arcsine state has negative values of WF when transmissivity is not equal to 1 or 0. The decoherence effect of the VAS is then studied by analytically deriving the time evolution formula of WF.     

用于CARS激发源的全光纤飞秒脉冲谱压缩

进行了基于光纤预啁啾和自相位调制的多模/单模组合式全光纤啁啾谱压缩研究.提出利用多模光纤模式估计群速度色散均值的方法,并将该估计值作为啁啾参量分析的计算参数,仿真计算了50/125μm折射率渐变多模光纤的群速度色散均值及其与单模光纤在不同长度比值下的光谱压缩效果.采用三种折射率渐变多模光纤进行实验,对比分析了折射率渐变多模光纤的芯径大小及其与单模光纤的长度比值对光谱压缩效果的影响.实验结果表明使用50/125μm折射率渐变多模光纤获得光谱最大压缩比为5.796,谱宽为2.243 nm,与理论仿真一致;使用105/125μm折射率渐变多模光纤,可进一步提高压缩比至152.941,输出谱宽为0.085 nm的光脉冲.将此脉冲用于相干反斯托克斯拉曼散射光谱探测,理论光谱分辨率可达1.386 cm~(-1).     

High-temperature impedance spectroscopy of BaFe0.5Nb0.5O3 ceramics doped with Bi0.5Na0.5TiO3

Bi_0.5Na_0.5TiO₃ (BNT)-doped BaFe_0.5Nb_0.5O₃ (BFN) ceramics were synthesized by a two-step solid-state reaction. Temperature dependence of dielectric properties measured at different frequencies was investigated over broad temperature and frequency ranges. Impedance spectroscopy and universal dielectric response were employed to study the relaxation behavior and conductivity mechanism of the ceramics in a frequency range from 40 Hz to 100 MHz and a temperature range from 300 K to 800 K. The complex plane impedance data revealed the bulk and grain boundary contributions toward conductivity processes in the form of semicircular arcs. The high-temperature conductivity of ceramics is attributable to thermally activated second ionized oxygen vacancy.     

使用PTB7作为阳极修饰层提高有机发光二极管的性能

采用poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-?uoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7)作为有机发光二极管器件的阳极修饰层,制备了结构为indium tin oxide(ITO)/PTB7(不同浓度)/N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)benzidine(NPB,40 nm)/8-hydroxyquinoline(Alq3,60 nm)/LiF(1 nm)/Al的系列器件,同时研究了不同浓度的PTB7对器件性能的影响.PTB7的最佳浓度为0.25 mg/mL,器件性能得到明显的改善,起亮电压为4.3 V.当驱动电压为14.6 V时,最大亮度为45800 cd/m2,最大电流效率为9.1 cd/A.与没有PTB7修饰的器件相比,其起亮电压降低了1.9 V,最高亮度提升了78.5%.器件性能提高归因于PTB7的插入使得空穴注入和传输能力大大改善.     

近地层大气光学湍流的分形和间歇性特征分析

利用光纤湍流测量系统获得了合肥西郊科学岛上气象观测场内下垫面平坦的水面上方0.48m、草地上方1.8m和23m高处的大气折射率起伏的观测数据,采用R/S分析法计算了近地层大气光学湍流的赫斯特指数和分形维数,统计分析了分形维数的日变化特征及概率分布特征。结果表明:对于一天的不同时段,分形维数在一定范围内动态变化,且中午时段相对稳定;在三种下垫面条件下,全天分形维数的值大多在1.3~1.4之间,其最可几概率位于1.35处,从均值来看,草地上方1.8m的分形维数最大,水面上方0.48m次之,草地上方23m处最小。最后,初步探讨了近地层大气光学湍流分形维数、间歇性指数和湍流发展程度的相关性。     

Narrowband optical parametric amplifier for efficient conversion of high-energy pulse with high beam quality

In a two-stage optical parametric amplifier based on KTiOAO4 crystals, we apply beam-overlapping technique to nanosecond signal pulse amplification, which results in high conversion efficiency and good beam quality. A signal pulse energy of 66 mJ at 1.572 μm wavelength is generated with 220 mJ of pump pulse input. A maximum gain of 66 and a maximum pump depletion of as high as 44% are determined. The spectral linewidth of the amplified signal pulse is around 50 MHz, and the beam quality factor of M 2 is less than 2.3.     

Influence of laser power density on damage of comb by photodynamic therapy—simulation and validation of mathematical models

Photodynamic therapy （PDT） has poor therapeutic outcomes for the treatment of port-wine stain （PWS） lesions with long drug-light intervals （DLIs）. This letter investigates the possibility of improving the treatment efficacy through increasing the laser power density using a computer simulation and a cock comb model. The computational model includes a Monte Carlo simulation for the laser distribution and a calculation of the singlet oxygen concentrations （102）. Both simulation and experimental results show that increasing the power density from i00 to 140 mW/cm^2 not only improves the PDT efficacy, but also results in the unwanted skin damage.     

巧用二极管的创新性实验

结合物理实验的教学功能,介绍几款巧用二极管的创新性物理实验的设计与制作。     

Corrosion resistance and blood compatibility of lanthanum ion implanted pure iron by MEVVA

Pure iron is a potential material applying for coronary artery stents based on its biocorrodible and nontoxic properties. However, the degradation characteristics of pure iron in vivo could reduce the mechanical stability of iron stents prematurely. The purpose of this work was to implant the lanthanum ion into pure iron specimens by metal vapor vacuum arc (MEVVA) source at an extracted voltage of 40 kV to improve its corrosion resistance and biocompatibility. The implanted fluence was up to 5 × 10¹⁷ ions/cm². The X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state and depth profiles of La, Fe and O elements. The results showed lanthanum existed in the +3 oxidation state in the surface layer, most of the oxygen combined with lanthanum and form a layer of oxides. The lanthanum ion implantation layer could effectively hold back iron ions into the immersed solution and obviously improved the corrosion resistance of pure iron in simulated body fluids (SBF) solution by the electrochemical measurements and static immersion tests. The systematic evaluation of blood compatibility, including in vitro platelets adhesion, prothrombin time (PT), thrombin time (TT), indicated that the number of platelets adhesion, activation, aggregation and pseudopodium on the surface of the La-implanted samples were remarkably decreased compared with pure iron and 316L stainless steel, the PT and TT were almost the same as the original plasma. It was obviously showed that lanthanum ion implantation could effectively improve the corrosion resistance and blood compatibility of pure iron.     

A compact passively Q-switched intra-cavity frequency doubled Nd:YAG/Cr4+:YAG composite crystal green laser

A compact diode-end-pumped passively Q-switched intra-cavity frequency doubled Nd:YAG/Cr⁴⁺:YAG composite crystal laser was demonstrated. The pulsed laser at 532 nm was produced and the dependence of the average out power, pulse width and pulse repetition rate on incident pump power were measured. Under the pump power of 14 W, the minimum pulse width of 3.5 ns with repetition rate of 27.5 kHz was obtained, corresponding single-pulse energy of 18 μJ and peak power of 5.3 kW.