How the effective boson-boson interaction works in Bose-Fermi mixtures in periodic geometries

We study mixtures of spinless bosons and not spin-polarized fermions loaded in two dimensional optical lattices. We approach the problem of the ground state stability within the framework of the linear response theory; by the mean of an iterative procedure, we are able to obtain a relation for the dependence of boson-boson effective interaction on the absolute temperature of the sample. Proceeding from such a formula, we write down analytical expressions for supersolid (SS) and phase separation (PS) transition temperatures, and plot the phase diagrams.     

绿光抽运准周期光学超晶格产生红光与蓝光的研究

使用一块准周期LiTaO3光学超晶格晶体,利用准相位匹配技术,通过光参变产生与和频两个非线性过程,将一束532nm绿色抽运光转变成666nm红光与443nm蓝光。具体过程为,通过参变过程获得红色信号光和红外闲频光,再通过绿色抽运光与红外闲置光和频获得蓝光,两个过程在同一块准周期光学超晶格中实现,准周期超晶格的两个倒易矢量分别补偿这两个过程中的相位失配。抽运光的脉宽为40ps,重复频率为10Hz,在平均功率为0．5mW时,测得红光和蓝光功率分别0．15mW和16．6μW,转换效率达到34％和3％。这一方法,提供了一种用一块超晶格晶体同时获得三原色输出的有效途径。     

双波长敏感的光致聚合物全息存储材料

介绍了一种以聚乙烯醇为粘结剂,丙烯酰胺和亚甲基双丙烯酰胺作为单体,赤藓红和亚甲基蓝作为光引发剂,三乙醇胺作为共引发剂的光致聚合物材料。材料能同时对红光和绿光敏感,用红光和绿光分别对材料曝光,测得的两种衍射效率分别不低于30％,灵敏度不低于25cm^2／J。该材料对红光的最大响应空间频率为2274 lp／mm,相应的衍射效率为27．73％,响应范围为1600∽2800lp／mm;对绿光的最大响应空间频率为2350 lp／mm．相应的衍射效率为25、72％,响应范围为1700∽3000 lp／mm。在材料的同一点上进行红光和绿光的波长复用全息存储,当用红光或绿光再现时单幅图像清晰,信噪比高,两幅图像之间无任何干扰,该材料适合双波长全息存储。     

正三角形及正方形微光学腔模式特性研究

微谐振腔模式特性研究是利用微腔研制新型光电器件的基础．为了研制出能采用平面工艺制作的定向输出的微腔激光器，文章采用解析和数值模拟方法深入研究了正三角形及正方形光学微腔的模式特性，并得到与数值模拟结果符合非常好的解析场分布及模式波长．对正方形光学微腔，把模式组合成满足正方形对称性的场分布，发现其类WG模式只存在品质因子比它小一个数量级以上的偶然简并模式，因此正方形微腔有利于实现真正的单模工作．     

Highly Selective Optical Detection of Fe3+ Ions in Aqueous Solution Using Label‐Free Silicon Nanocrystals

High brightness amine‐terminated silicon nanocrystals (Si NCs) have been utilized in a simple and rapid assay for the highly selective and sensitive detection of Fe³⁺ via quenching of their strong blue luminescence, without the need for analyte‐specific labeling groups. Sensitive detection of Fe³⁺ is successfully demonstrated, with a linear relationship observed between luminescence quenching and Fe³⁺ concentration from 5 × 10^?6 to 900 × 10^?6m and a limit of detection of 1.3 × 10^?6m . The Si NCs show excellent selectivity toward Fe³⁺ ions, with no quenching of the luminescence signal induced by the presence of Fe²⁺ ions, allowing for solution phase discrimination between the ionic species in different charge states.     

TheB 2Σ-X 2Σ system of the CaF molecule

The spectrum of theB ²Σ-X ²Σ system of the CaF molecule has been photographed in the second order of a 10.6 m concave grating spectrograph with 0.33 Å/mm dispersion. The rotational structure of the (0, 0) and (1, 0) bands has been analysed and the precise molecular constants have been obtained. Using the constants so determined the band origins of a large number of bands with 0 <v′,v″ < 10 have been calculated and used to obtain the accurate vibrational constants forB andX states and these are presented.     

超分辨重建技术及其研究进展

超高分辨成像技术一直是航天、遥感、目标识别等领域的研究热点。随着光学成像到光电数字成像的转变,如何提高CCD的几何分辨率,已成为研制高分辨光电成像系统亟待解决的问题。本文从理论和工程实现的角度介绍了超分辨成像的技术原理,分析了实现超分辨重建技术的几种方法,主要描述了微扫描和亚像元两种重建技术的实现方式,指出了目前超分辨技术存在的缺陷。最后,针对超分辨技术中无混淆重建带宽较窄的问题,提出了一种新的技术方案。该方案将光学编码技术与目前的亚像元技术相结合,可将重建带宽拓展3倍。研究结论指出：融合了光学,光电子学和信号处理的成像系统的综合设计,将是未来成像领域的一个重要研究方向。     

单晶YSZ的Xe+离子辐照效应研究

200keV Xe+离子辐照使单晶YSZ由无色透明变成紫色透明,结果表明,能量为200keV,注量为1×1017cm-22的Xe+离子辐照YSZ单晶产生的损伤高达350dpa,在损伤区产生高密度的缺陷,但仍然没有发生非晶化转变。吸收光谱测试结果表明,产生吸收带的注量阈值大约为1016cm-2。注量为1×1016cm-2和1×1017cm-2的样品,吸收带峰值分别位于522nm和497nm。光吸收带可能与Zr阳离子最近邻的氧空位捕获电子形成的F型色心和Y阳离子近邻的氧离子捕获空穴形成的V型色心有关。     

New results on quadratic stabilization of switched linear systems with polytopic uncertainties

^** Corresponding author. Email: longwang{at}pku.edu.cn^*** Email: jizj{at}mech.pku.edu.cn In this paper, the quadratic stabilization of switched linearsystems with polytopic uncertainties is considered. Comparedwith the existing result, a more general switching control methodis proposed to guarantee the quadratic stabilization. This switchingcontrol method is based on the partition of the vertex matrixset of each subsystem. By this method, the matrix inequalitiesneeded to be solved are always less than those needed to besolved before except one extreme case; for this case, it isequal. The switched control synthesis problem is also studiedfor both switched state feedback and output feedback. Severalbilinear matrix inequality based conditions are derived forboth cases.