40 Gb/s, secure optical communication based upon fast reconfigurable time domain spectral phase en/decoding with 40 Gchip/s optical code and symbol overlapping

We propose and experimentally demonstrate a 40 Gb/s secure optical communication system with on-off-keying (OOK) modulation format by using a time domain spectral phase en/decoding scheme, which employs a highly dispersive element and high-speed phase modulator for introducing significant symbol overlapping for both the encoded and incorrectly decoded noiselike signals to enhance the information security against eavesdropping using a power detector. The influence of dispersion and chip modulation rate on the symbol overlapping of the incorrectly decoded signal has been analytically investigated and experimentally verified. Security enhancement for 40 Gb/s OOK data using fast reconfigurable 40 Gchip/s optical codes with code lengths of up to 1024 has been demonstrated and compared with a 10 Gb/s system.     

溴到铷的类钠离子能级辐射跃迂几率和能级寿命

本文在多组态Dirac-Fock(MCDF)理论框架下计算了水窗波段(λ:23.3～43.8A,相当于Z:34～46)的溴到铷的类钠离子1s~22s~22p~6nlj(n=3～15,l=0～6)各能级能量及各能级n_il_ij_i—n_kl_kj_k(n_i≤6,n_h≤15)间的电偶极辐射跃迁几率,并由此得出可能产生软X射线激光跃迁(4f-5g,4d-5f,4f-6g,4d-6f)的激光上能级的寿命,把计算得到的跃迁波长与实验测量值进行比较,其相对误差小于0.35％。     

GaAs被动调Q Nd:YAG激光器激光特性的研究

报道了用半导体材料 Ga As实现氙灯抽运 Nd:YAG激光器的被动调 Q运转 ,测量了激光器的阈值、脉冲宽度和输出能量。从 Ga As的能级结构出发 ,理论上研究了 Ga As材料的饱和吸收原理 ,建立了调 Q激光器速率方程并给出了数值解 ,对理论结果与实验结果进行了比较和讨论。     

红外光谱统计波长选择方法用于废气检测

为了从含有噪声的大气红外光谱中提取微量待测污染组分的定量特征,进而建立校正模型,本文提出了一种基于统计理论的波长选择方法。该方法针对待测组分,在对光谱各波长位置的噪声强度进行统计估计的基础上,提出了选择最佳波长子集的目标函数。该目标函数包含波长子集的噪声和长度参数,这使得在最小化模型误差的同时也防止了模型规模的无限制膨胀。为了检验该方法的性能。文章利用含背景噪声的实测光谱数据针对三种气体进行了波长选择,并利用神经网络技术分别建立了校正模型。实验结果与波长子集的优化结果相符,所选择的波长子集的长度不足光谱波长总点数的2％,同时,光谱中的噪声也在校正模型中得到了明显的抑制。实验结果证明了该波长选择方法的有效性。     

非晶态Fe0.5Al0.5PO4表面上激光促进甲烷直接氧化合成甲醇的研究

用溶胶－凝胶法合成了非晶态Ｆｅ０．５Ａｌ０．５ＰＯ４。用ＸＲＤ和ＴＰＲ表征了其结构和晶格氧的活性;用ＩＲ和ＴＰＤ表征了ＣＨ４在其表面上的吸附行为;用ＬＳＳＲ方法考察了ＣＨ４直接氧化合成ＣＨ３ＯＨ的反应规律。结果表明,Ｆｅ０．５Ａｌ０．５ＰＯ４具有非晶态的结构,ＦｅＰＯ４和ＡｌＰＯ４的微区被均匀地相互隔离,导致固体本身不具有长程有序性。非晶态的Ｆｅ０．５Ａｌ０．５ＰＯ４与晶态的Ｆｅ０．５Ａｌ０．５Ｐ     

激光光束传输因子M2的一些问题

本文讨论与M²因子有关的一些问题,指出在近轴近似条件下由光束的二阶强度矩定义的M²因子满足M²≥1,其中只有对基模高斯光束等式才成立.由光束的功率通量值定义的M²因子(M_pc²)有可能小于1,M_pc²的大小取决于所定义的光斑半径内包含的光功率的百分数.通过计算光场的二阶矩,我们获得了轴向相干叠加的高斯光束的M²因子的解析解.     

利用衍射光学技术进行激光光强叠加的研究

采用模拟退火算法研究了利用衍射光学元件(DOE)进行激光光强叠加的可能性,并分析了由于蚀刻误差和入射激光束位置偏离引起的误差.数值模拟结果表明在DOE相位是16阶量化的情况下,设计误差小于1.7e-3,效率大于98.9%,可以很好地实现光束叠加功能.     

Note on rare Z-boson decays to double heavy quarkonia

Within the standard model, we have investigated rare Z-boson decays into double heavy quarkonia, \begin{document}$ Z\to VV $\end{document} and \begin{document}$ Z\to VP $\end{document}, with V and P denoting vector and pseudoscalar quarkonia, respectively. It is assumed that the leading-order QCD diagrams would give the dominant contributions to these processes, and the corresponding branching fractions, for instance, \begin{document}$ {\cal B}(Z\to J/\Psi J/\Psi) $\end{document}, have been estimated to be approximately\begin{document}$ 10^{-13} $\end{document} in literature. However, these decays could also happen through electromagnetic transitions \begin{document}$ Z\to V\gamma^* $\end{document} and \begin{document}$ Z\to P\gamma^* $\end{document}, with the virtual photon transforming into V. Interestingly, the smallness of the vector quarkonium mass can give rise to a large factor \begin{document}$ m_Z^2/m_V^2 $\end{document} relative to the QCD contributions, which thus counteracts the suppression from the electromagnetic coupling. We systematically include these two types of contributions in our calculation to predict branching fractions for these decays. Particularly, owing to the virtual photon effects, it is found that \begin{document}$ {\cal B}(Z\to J/\Psi J/\Psi) $\end{document} will be significantly enhanced, up to \begin{document}$ 10^{-10} $\end{document}.     

苄基保护甘露糖羧酸酯的NMR研究

应用NMR技术研究了1-0-(3,5-二硝基苯甲酰基)-2、3、4、6-四-0-苄基-D-吡喃甘露糖的α、β异构体的构型和糖环上碳氢归属情况,总结了苄基保护甘露糖羧酸酯构型的确证方法及影响糖环上碳氢化学位移的一些规律;并对其它13种四苄基甘露糖羧酸酯的NMR谱进行了研究,提供了这些化合物的¹³C和¹H NMR数据.     

Z=18—82原子的同步辐射内壳层光电离积分截面的计算和讨论

此文计算了Ｚ＝１８－８２的原子在北京同步辐射４Ｂ９Ａ束线的白色Ｘ光照射下的光电离积分截面Ｇ值。结果表明，有三个Ｇ值较大的区域，Ｚ＝１８－２０，３９－４７和５９－８２，最大值分别为３．８×１０－６，１．６×１０－５和３．５×１０－５ｐｈｏｔｏｎｓ·ｃｍ２／ｓ。同时，估计了平衡时主要多重电荷态离子数目，分析了用同步辐射和离子阱进行多重电荷态实验的新的候选原子，讨论了有关实验方法和技术。