ZnO/ZnS核-壳量子点的双光子吸收效应

利用飞秒激光Z-扫描与泵浦-探测技术,研究了室温下ZnO/ZnS与ZnO/ZnS/Ag核-壳胶体量子点的双光子吸收效应.研究发现:ZnO基核-壳量子点的本征双光子吸收系数比ZnO体材料增大了3个数量级;测量得到的660 nm处的ZnO/ZnS核-壳量子点双光子吸收截面约为4.3×10^-44 cm⁴·s·photon^-1,比相应的ZnS、ZnSe及 CdS量子点大2个数量级;当ZnO/ZnS核-壳量子点镶嵌了银纳米点时,非线性吸收有所增强.ZnO基复合纳米结构的双光子吸收增强可归因于量子限域与局域场效应.     

520nm泵浦780nm+1560nm双共振光学参量振荡器

我们在实验中演示了520nm单频绿光泵浦的基于周期极化磷酸钛氧钾(PPKTP)晶体的780nm+1560nm双共振光参量振荡器,高效制备780nm+1 560nm连续可调谐双色下转换光场。该参量振荡器可输出93.3 mW的1 560nm单频激光和44.6mW的780nm单频激光。通过改变PPKTP晶体的温度所得到的波长粗调范围为:信号光1 529.81nm~1 573.83nm(~44nm),闲置光788.26nm~777.20nm(~11nm);通过连续调谐520nm泵浦激光频率初步得到的闲置光在780.24nm(铷原子D2线)处频率连续调谐范围约1.6GHz。     

大型相关失效工程网络系统可靠度的近似算法

为避开失效模式(或系统可靠路径)的NP难题(non—polynomial increase hard problem)，提出递推分解算法，降低大型工程网络系统可靠度分析中的计算复杂性，同时，将改进的多维正态变量积分公式，引入递推分解算法之中，计算多失效模式(或系统可靠路径)的联合概率，并最终计算工程网络系统的失效概率和可靠度，对于特别复杂的工程网络系统，采用上下界的方法，给出具有很高精度的可靠度近似值。实例分析表明，本文提出的方法，具有较高的精度和计算效率。     

Structural first failure times under non-Gaussian stochastic behavior

An analytical moment-based method for calculating structural first failure times under non-Gaussian stochastic behavior is proposed.In the method,a power series that constants can be obtained from response moments (skewness,kurtosis,etc.) is used firstly to map a non-Gaussian structural response into a standard Gaussian process,then mean up-crossing rates,mean clump size and the initial passage probability of a critical barrier level by the original structural response are estimated,and finally,the formula for calculating first failure times is established on the assumption that corrected up-crossing rates are independent.An analysis of a nonlinear single-degree-of-freedom dynamical system excited by a Gaussian model of load not only demonstrates the usage of the proposed method but also shows the accuracy and efficiency of the proposed method by comparisons between the present method and other methods such as Monte Carlo simulation and the traditional Ganssian model.     

Identification and separation of local and nonlocal optical nonlinear refraction effects: theory and experiment

Understanding the nonlinear optical effect of novel materials plays a crucial role in the fields of photonics and optoelectronics. Herein, we theoretically and experimentally investigate the simultaneous presence of third-order locally refractive nonlinearity and thermally induced nonlocal nonlinearity saturation. We present analytical expressions for the closed-aperture Z-scan trace and the number of spatial self-phase modulation(SSPM) rings,which allows one to unambiguously and conveniently separate the contributions of local and nonlocal nonlinear refraction in the case that both effects occur simultaneously. As a test, we study both the local and thermally induced nonlocal nonlinear refraction in fullerene/toluene solution by performing continuous-wave Z-scan and SSPM measurements at two different wavelengths. This work enriches the understanding of the physical mechanism of the optical nonlinear refraction effect in solution dispersions of nanomaterials, which can be exploited for nonlinear photonic devices.     

不同光场二阶相干度的实验研究

基于Hanbury Brown-Twiss(HBT)实验,我们借助于两个单光子计数模块,一个50/50分束器和一个快速计数卡(FastCom-P7888)研究了不同光场的二阶相干度。我们首先制备了脉冲相干光,连续相干光以及单原子发出的单光子源,并测量这几种不同光场的二阶相干度g(2)(τ)。我们通过测量俘获在磁光阱(MOT)和远失谐偶极阱(FORT)中的单原子在近共振连续激光激发下所辐射的荧光的二阶相干度,分别得到了g(2)(τ=0)=0.08和g(2)(τ=0)=0.09,借助于实验中产生的脉冲光与单原子,接下来我们将进行触发式单光子源的实验研究。     

微型光学偶极阱中单原子相干操控Rabi振荡的实现及其应用

文章综述了Rabi振荡的基本原理以及微型光学偶极阱中单原子相干操控Rabi振荡的研究进展,同时介绍了其在单光子源、量子寄存器、量子计算等方面的应用,并简要介绍了作者所在小组在微型光学偶极阱中单原子操控方面的实验进展.     

Cr2O3和CrO3/Cr2O3催化剂的2-氯-1,1,1-三氟乙烷气相氟化反应的活性物种和失活

采用沉淀法和浸渍法制备了2种铬基（Cr₂O₃和CrO₃/Cr₂O₃）催化剂,用于气相氟化2-氯-1,1,1-三氟乙烷合成1,1,1,2-四氟乙烷。研究发现含有低价铬（Cr³⁺）物种的Cr₂O₃催化剂上2-氯-1,1,1-三氟乙烷的稳态转化率为18.5%,而含有高价铬（Cr⁶⁺）物种和低价铬（Cr³⁺）物种的CrO₃/Cr₂O₃催化剂初始转化率达到30.6%,然而存在明显的失活。含有Cr⁶⁺物种的CrO₃/Cr₂O₃催化剂的2-氯-1,1,1-三氟乙烷氟化反应初始TOF值为1.71×10^-4 mol_HCFC-133a·mol_Cr（Ⅵ）^-1·s^-1,高于含有Cr³⁺物种的Cr₂O₃催化剂（4.16×10^-5 mol_HCFC-133a·mol_Cr（Ⅲ）^-1·s^-1）。Cr₂O₃催化剂在氟化反应前后催化剂的物相结构保持不变;而含有高价铬物种的CrO₃/Cr₂O₃催化剂经HF反应后生成了CrO_xF_y活性物种。然而,CrO_xF_y物种在反应中挥发或转化成稳定但无活性的CrF₃,从而导致催化剂失活。     

Possible hidden-charm molecular baryons composed of an anti-charmed meson and a charmed baryon

Using the one-boson-exchange model, we studied the possible existence of very loosely bound hidden-charm molecular baryons composed of an anti-charmed meson and a charmed baryon. Our numerical results indicate that the Σ_cD^* and Σ_cD states exist, but that the Λ_cD and Λ_cD^* molecular states do not.