微腔增强发射的半导体量子点单光子源

单光子源是实现量子密匙分配、线性光学量子计算的基本单元。作者回顾了单光子源在量子信息科学发展中的作用,讨论了光子的统计特性,分析了具有类似原子二能级结构的半导体量子点作为单光子发射源的特点,介绍了微腔与二能级系统的耦合以及微腔量子电动力学基本原理。在弱耦合区,Purcell效应导致微腔中量子点激子复合寿命降低,因此可用微腔来改善量子点单光子发射效率。文章总结了近年来在半导体微腔增强量子点单光子发射领域的进展,探讨了分布式布拉格反射微腔、柱状微腔和光子晶体微腔等结构对改善半导体量子点单光子发射和收集效率、光子极化以及光子全同性等方面的作用,并对未来半导体量子点单光子源的发展进行了展望。     

掺杂对CH样品Rayleigh-Taylor不稳定性增长的影响

在神光II激光装置上进行了辐射驱动不同掺杂样品的单模Rayleigh-Taylor(RT)不稳定性实验.结果显示:与纯碳氢(CH)样品相比,掺Br的CH样品的扰动更早、更快地进入非线性区,产生二次谐波,并且掺Br比例越高,CH样品扰动进入非线性区的时间越早,相同时刻扰动的二次谐波的幅度越高.这是因为密度梯度效应抑制了二次谐波的产生,掺Br比例越高,密度梯度标长越小;同时密度梯度效应还抑制三次谐波对基模增长的负反馈,造成基模具有更大的线性增长,导致线性饱和幅值大于经典值0.1λ.     

Tunable light emission and decaying process of photoluminescence from a nanostructured Si-in-SiNx film

Strong photoluminescence (PL) covering the green-violet band was measured at room temperature in an as-deposited amorphous Si-in-SiN_x film, which was prepared by plasma-enhanced chemical vapor deposition on cold (below 60 °C) Si(1 0 0) wafer. With an increase in photon energy of excitation, the PL shifts its peak position from 510 to 416 nm at yet-comparable intensities, thus allowing an energy-selected excitation in practical application. Also, a time-resolved analysis was performed for the emissions at various wavelengths, which showed a decay time shorter than 1.0 ns. These results indicate that the nanostructured Si-in-SiN_x can be a promising candidate material for the fabrication of silicon-based optical interconnections and switches.     

锕系核集体运动的负宇称态

从锕系区40多个核的正负宇称态的实验数据,如激发能、J^π、电偶极跃迁等,得到一系列与核结构有关的物理量,如宇称劈裂能级差δE_I,正负宇称带的第一和第二类转动惯量J⁽¹⁾和J⁽²⁾及第一负宇称态的电偶极跃迁强度比等,以及它们与角动量I或转动角频率ω的动力学和核子数A的系统行为,从而为研究锕系核负宇称态的产生机制及动力学特点提供了信息.     

Accurate, high-order representation of complex three-dimensional surfaces via Fourier continuation analysis

We present a new method for construction of high-order parametrizations of surfaces: starting from point clouds, the method we propose can be used to produce full surface parametrizations (by sets of local charts, each one representing a large surface patch – which, typically, contains thousands of the points in the original point-cloud) for complex surfaces of scientific and engineering relevance. The proposed approach accurately renders both smooth and non-smooth portions of a surface: it yields super-algebraically convergent Fourier series approximations to a given surface up to and including all points of geometric singularity, such as corners, edges, conical points, etc. In view of their C^∞ smoothness (except at true geometric singularities) and their properties of high-order approximation, the surfaces produced by this method are suitable for use in conjunction with high-order numerical methods for boundary value problems in domains with complex boundaries, including PDE solvers, integral equation solvers, etc. Our approach is based on a very simple concept: use of Fourier analysis to continue smooth portions of a piecewise smooth function into new functions which, defined on larger domains, are both smooth and periodic. The “continuation functions” arising from a function f converge super-algebraically to f in its domain of definition as discretizations are refined. We demonstrate the capabilities of the proposed approach for a number of surfaces of engineering relevance.     

相变域硅薄膜材料的光稳定性

采用RF-PECVD技术，通过改变反应气体的硅烷浓度制备了一系列不同晶化率不掺杂的硅薄膜材料，研究了工艺变化对材料结构的影响及材料光电特性同微结构的关系.随后进行了光衰退试验，在分析光照前后光电特性变化规律的基础上，认为材料中的非晶成分是导致材料光电特性衰退的主要原因.在靠近过渡区非晶一侧的硅材料比普通非晶硅稳定，衰退率较少；高晶化率微晶硅材料性能稳定，基本不存在光衰退；在靠近过渡区微晶一侧的硅材料虽然不是完全不衰退，但相比高晶化率硅材料来说更适合制备高效微晶硅电池. 关键词： 射频等离子体增强化学气相沉积 硅薄膜 Staebler-Wronski(SW)效应 稳定性     

考虑量子效应的Zakharov方程组的孤波解

借助Maple程序，利用扩展的双曲函数法和双函数法求解了考虑量子效应的Zakharov方程组，得到了多种孤波解，其中包括亮孤波解、W型孤波解、M型孤波解和奇性孤波解. 关键词： 量子效应 Zakharov方程组 扩展的双曲函数法 孤波解     

密闭高温高压溶样ICP-MS测定24个国际地质标样中的Sb和Bi

研究了ICP-MS分析中Bi,Sb,Te和As产生的记忆效应,其记忆效应Bi>Sb>Te>As。在低浓度硝酸介质中(0.01%～1%),贮存样品的聚丙烯瓶和ICP-MS的进样管道会对Bi元素产生严重的吸附作用。0.1%氢氟酸的清洗效果优于6%的硝酸,而6%的硝酸的清洗效果要优于0.1%高氯酸。在给定的仪器操作条件下,Sb和Bi的检出限分别为0.001和0.000 1 ng·mL-1。采用该清洗方法,结合密闭高温高压溶样,测定了24个国际地质标样中的Bi和Sb。大部分标样的测定结果与已有参考值吻合较好。文章还给出了国际标样AGV-2(安山岩)、BHVO-2(玄武岩)和BCR-2(玄武岩)中Bi和Sb的测定值。     

甲醇在γ-Al2O3,CeO2及其负载Pd催化剂上吸附和分解的原位红外光谱研究

利用原位傅里叶变换红外光谱 (FTIR)技术对甲醇在γ Al2 O3,CeO2 以及Pd/Al2 O3,Pd/CeO2 催化剂上的吸附和分解行为进行了研究。综合考虑了载体和活性组分的作用 ,分析了甲醇在不同载体负载Pd催化剂上可能的分解途径。在Pd/CeO2 催化剂上 ,活性组分和载体对甲醇分解的过程表现出了一种协同效应。     

Enhancement of charge and spin Seebeck effect in triple quantum dots coupling to ferromagnetic and superconducting electrodes

We theoretically study the thermoelectric transport properties through a triple quantum dots (QDs) device with the central QD coupled to a ferromagnetic lead, a superconducting one, and two side QDs with spin-dependent interdot tunneling coupling. The thermoelectric coefficients are calculated in the linear response regime by means of nonequilibrium Green's function method. The thermopower is determined by the single-electron tunneling processes at the edge of superconducting gap. Near the outside of the gap edge the thermopower is enhanced while thermal conductance is suppressed, as a result, the charge figure of merit can be greatly improved as the gap appropriately increases. In the same way, charge figure of merit also can be greatly improved near the outside of the gap edge by adjusting interdot tunneling coupling and asymmetry coupling of the side QDs to central QD. Moreover, the appropriate increase of the interdot tunneling splitting and spin polarization of ferromagnetic lead not only can improve charge thermopower and charge figure of merit, but also can enhance spin thermopower and spin figure of merit. Especially, the interdot tunneling splitting scheme provides a method of controlling charge (spin) figure merit by external magnetic field.