High-Q TM whispering-gallery modes in three-dimensional microcylinders

We present a generation condition for realizing high-Q TM whispering-gallery modes (WGMs) in semiconductor microcylinders. For microcylinders with symmetry or weak asymmetry vertical waveguiding, we show that TM WGMs can have a high Q factor, with the magnitude of 10(4) at the radius of the microcylinder of 1 mu m, by three-dimensional numerical simulation. The Q factor of TE WGMs is much less than that of TM WGMs in the semiconductor microcylinders due to a vertical radiation loss caused by mode coupling with the vertical propagating mode. The results open up a possible application of TM WGMs in semiconductor microcylinders for efficient current injection microlasers and single photon sources.

The role of Sb in the molecular beam epitaxy growth of 1.30-1.55 mu m wavelength GaInNAs/GaAs quantum well with high indium content

Sb-assisted GaInNAs/GaAs quantum wells (QWs) with high (42.5%) indium content were investigated systematically. Transmission electron microscopy, reflection high-energy electron diffraction and photoluminescence (PL) measurements reveal that Sb acts as a surfactant to suppress three-dimensional growth. The improvement in the 1.55 mu m range is much more apparent than that in the 1.3 mu m range.. which can be attributed to the difference in N composition. The PL intensity and the full-width at half maximum of the 1.55 mu m single-QW were comparable with that of the 1.3 Am QWs. (c) 2006 Elsevier B.V. All rights reserved.

Mode characteristics for equilateral triangle optical resonators

Mode characteristics of equilateral triangle resonators (ETRs) are analyzed based on the symmetry operation of the point group C-3v. The results show that doubly degenerate eigenstates can be reduced to the A(1) and A(2) representations of C-3v, if the longitudinal mode number is a multiple of 6; otherwise, they form the E irreducible representation Of C-3v. And the one-period length for the mode light ray is half of the perimeter of the ETR. Mode Q-factors are calculated by the finite-difference time-domain (FDTD) technique and compared with those calculated from far-field emission based on the analytical near-field pattern for TE and TM modes. The results show that the far-field emission based on the analytical field distribution can be used to estimate the mode Q-factor, especially for TM modes. FDTD numerical results also show that Q-factor of TE modes reaches maximum value as the longitudinal mode number is a multiple of 7. In addition, photoluminescence spectra and measured Q-factors are presented for fabricated ETR with side lengths of 20 and 30 mu m, and the mode wavelength intervals are compared with the analytical results.

Analysis of the interfaces of [NiFe/Mo](30) and [Fe/Mo](30) multilayers

The interface states of [NiFe/Mo](30) and [Fe/Mo](30) multilayers have been investigated by x-ray small angle reflection and diffuse scattering. Significant interface roughness correlation was observed in both ultrathin [NiFe/Mo](30) and [Fe/Mo](30) multilayers. An uncorrelated roughness of about 27-3.1 Angstrom was revealed in the [NiPe/Mo](30) multilayers, which is explained as originating from a transition layer between the NiFe and the Mo layers. By the technique of diffuse scattering, it is clearly indicated that the interfacial roughness of NiFe/Mo is much smaller than that of Fe/Mo although the lattice mismatch is the same in both multilayers.

High Q-factor TM modes in three-dimensional semiconductor microresonators

We have investigated the mode characteristics for three-dimensional (3D) semiconductor microresonators by finite-difference time-domain (FDTD) technique. The results show that the quality-factors (Q-factors) of TM-like modes are much larger than those of TE-like modes as the vertical waveguidng formed by semiconductor materials.

Continuous-wave electrically injected InP/GaInAsP equilateral-triangle-resonator lasers

Equilateral-triangle-resonator (ETR) microlasers with an output waveguide connected to one of the vertices of the ETR are fabricated using standard photolithography and inductively-coupled-plasma etching techniques. Continuous-wave electrically injected 1550 nm ETR laser with side length ranged from 15 to 30 tm are realized at room temperature.

Study on the hydrolysis/precipitation behavior of Keggin Al-13 and Al-30 polymers in polyaluminum solutions

The hydrolysis/precipitation behaviors of Al3+, Al-13 and Al-30 under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl3, PAC(A113) and PAC(A130) were 6.5-7.5, 8.5-9.5, and 7.5-9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl3 >> PAC(A130) > PACA113. The precipitates' size increased when the dosage increased from 50 mu M to 200 mu M, but it decreased when the dosage increased to 800 AM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The isoelectric points of the freshly formed precipitates for AlCl3, PAC(A113) and PAC(A130) were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl3 hydrolysis precipitates were lower than those of PAC(A113) and PAC(A130) when pH > 5.0. The Zeta potential of PAC(A130) hydrolysis precipitates was higher than that of PACA113 at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al-Ferron research indicated that the hydrolysis precipitates of AlCl3 were composed of amorphous AI(OH)3 precipitates, but those of PACA113 and PACA130 were composed of aggregates of Al-13 and Al-30, respectively. Al3+ was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al-13 and Al-30 species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al-Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al--Ferron method. The chemical composition of Al-a, Al-b and Al-c depended on coagulant and solution pH. The Al-b measured in the current case was different from Keggin Al-13, and the high Alb content in the AlCl3 hydrolysis precipitates could not used as testimony that most of the Al3+ Was converted to highly charged Al-13 species during AlCl3 coagulation.

On the acid-base stability of Keggin Al-13 and Al-30 polymers in polyaluminum coagulants

The acid-base stabilities of Al-13 and Al-30 in polyaluminum coagulants during aging and after dosing into water were studied systematically using batch and flow-through acid-base titration experiments. The acid decomposition rates of both Al-13 and Al-30 increase rapidly with the decrease in solution pH. The acid decompositions of Al-13 and Al-30 with respect to H+ concentration are composed of two parallel first-order and second-order reactions, and the reaction orders are 1.169 and 1.005, respectively. The acid decomposition rates of Al-13 and Al-30 increase slightly when the temperature increases from 20 to ca. 35 A degrees C, but decrease when the temperature increases further. Al-30 is more stable than Al-13 in acidic solution, and the stability difference increases as the pH decreases. Al-30 is more possible to become the dominant species in polyaluminum coagulants than Al-13. The acid catalyzed decomposition and followed by recrystallization to form bayerite is one of the main processes that are responsible for the decrease of Al-13 and Al-30 in polyaluminum coagulants during storage. The deprotonation and polymerization of Al-13 and Al-30 depend on solution pH. The hydrolysis products are positively charged, and consist mainly of repeated Al-13 and Al-30 units rather than amorphous Al(OH)(3) precipitates. Al-30 is less stable than Al-13 upon alkaline hydrolysis. Al-13 is stable at pH < 5.9, while Al-30 lose one proton at the pH 4.6-5.75. Al-13 and Al-30 lose respective 5 and 10 protons and form [Al-13] (n) and [Al-30] (n) clusters within the pH region of 5.9-6.25 and 5.75-6.65, respectively. This indicates that Al-30 is easier to aggregate than Al-13 at the acidic side, but [Al-13] (n) is much easier to convert to Alsol-gel than [Al-30] (n) . Al-30 possesses better characteristics than Al-13 when used as coagulant because the hydrolysis products of Al-30 possess higher charges than that of Al-13, and [Al-30] (n) clusters exist within a wider pH range.

Prediction of simultaneously large and opposite generalized Goos-Hanchen shifts for TE and TM light beams in an asymmetric double-prism configuration

It is predicted that large and opposite generalized Goos-Hanchen (GGH) shifts may occur simultaneously for TE and TM light beams upon reflection from an asymmetric double-prism configuration when the angle of incidence is below but near the critical angle for total reflection, which may lead to interesting applications in optical devices and integrated optics. Numerical simulations show that the magnitude of the GGH shift can be of the order of beam's width.

30.4nm极紫成像探测器实验研究

中国科学院知识创新方向性项目(061Z291213) 资助课题

人类带3蛋白胞质片段的表达纯化及其性质表征

带3蛋白胞质片段(cdb3)具有多种生理功能：它可以将膜和膜骨架蛋白相联，起着维持细胞形状以及沟通内外环境的作用。而且，它还通过与多个糖酵解酶的相互作用来调节红细胞内糖酵解速率。它的这些功能很大程度上归因于它的分子柔性大，可以通过各种构象与膜蛋白、糖酵解酶等竞争性结合。 在本文中，我们首先运用分子克隆技术在大肠杆菌BL21(DE3)中成功地构建pET28b-cdb3表达体系。经37℃培养至OD600达0.6时，加入1mM IPTG ，于30℃诱导表达cdb3蛋白。经离子交换和亲和层析两步纯化得到电泳纯的具有生物活性的cdb3蛋白。之后，我们首次较为系统地表征了cdb3蛋白的构象特点：在常规的生理环境下, cdb3蛋白呈现典型的α-螺旋、β折叠二级结构， cdb3的四个Trp残基很大程度地包埋于疏水环境中；随溶液GuHCl浓度增加，cdb3 的四个Trp残基逐渐暴露于极性环境中；当pH值从6.0升高到10.0时，cdb3的Tm值逐渐降低约15℃，其内源荧光强度增加两倍，并在pH 7.2和pH9.2处呈现拐点，而蛋白的二级结构却没有发生变化。金属离子Cd2+、Ca2+、Cu2+、Co2+、Mg2 、Zn2+的结合位点在cdb3蛋白的Trp残基附近，而50μM的金属离子对重组cdb3蛋白的二级结构影响微小。最后，我们合成了cdb3蛋白N端肽段1－23，发现其在水溶液中呈无规卷曲结构，TFE可诱导其形成α螺旋，当TFE浓度增至80%时α螺旋含量达最高。无规卷曲的肽段不与醛缩酶相结合，其以α螺旋形式与醛缩酶相结合。 ATP可与肽段、重组cdb3蛋白结合，并对其光谱学性质有一定影响。当ATP浓度达到3mM时，重组cdb3蛋白发生聚集。

分子组装体的扫描探针显微学研究

本文简要评述了扫描探针显微学研究的发展过程、目前状况及发展方向，着重介绍了扫描探针显微学(SPM)在分子组装体研究中的一些应用。采用扫描探针显微学结合电化学的方法对自组装膜(SAMs)、表面活性剂(surfactant)、纳米颗粒(nanoparticles)等分子组装体系进行了研究，并结合IR、QCM、XPS、XRD等多种手段对分子组装体在电极表面的形态和结构进行了探讨。主要结果如下：1．SPM研究以杂多酸为基础的分子组装体我们通过将AsMo_(11)V0_(40)~(4-)杂多酸阴离子从其酸性溶液中自吸附至金表面的方法，制备了一类新的无机自组装膜。我们利用QCM、STM和电化学方法分别研究了AsMo_(11)VO_(40)~(4-)自组装膜的吸附过程、在Au表面的结构和电化学性质。QCM数据表明这个自组装过程可以用Langmuir吸附等温式来描述，其吸附自由能为-20 KJ/mol。 通过QCM测得的AsMo_(11)VO_(40)~(4-)自组装膜的表面覆盖度的最大值为1.7 * 10~(-10)mol/cm~2，这相当于一个AsMo_(11)VO_(40)~(4-)阴离子的密堆积单层。AsMo_(11)VO_(40)~(4-)自组装膜的循环伏安图上出现三对可逆的氧化还原峰，每对峰所对应的自组装膜的表面覆盖度都亦为1.78 * 10~(-10) mol/cm2，和QCM结果一致。现场STM图像显示AsMo_(11)VO_(40)~(4-)自组装膜十分的均一没有如何多层或聚集体的结构。高分辨STM图进一步显示在Au(111)表面的sMo_(11)VO_(40)~(4-)自组装膜于+0.7 V(vs．Ag | AgCl)表现出二维有序的四方晶体结构，晶格间距为10-11 A。这个值与sMo_(11)VO_(40)~(4-)阴离子的直径十分接近。从STM图我们也估算出AsMo_(11)VO_(40)~(4-)自组装膜的表面覆盖度为1.8 * 10~(-10) mol/cm~2，这和QCM以及电化学的实验结果都很接近。我们进一步研究了一种新的以杂多酸为基础的有机无机复合膜--砷钼钒杂多酸的十一烷基吡啶盐(CPMVA)--的制备、结构和电催化性质。通过在这种盐的丙酮溶液中循环电位扫描，我们可以在HOPG电极表面制备稳定的CPMVA膜。我们利用XPS、STM和电化学多种手段来表征CPMVA膜的结构和性质。这些研究表明：在新剥离HOPG表面CPMVA膜的结构为自聚集的分子团，而在预阴极化HOPG表面CPMVA膜的结构为自有序单层。CPMVA膜在酸性和丙酮溶剂中部表现出可逆的氧化还原动力学行为，这说明这种新类型的膜甚至能在有机溶剂中用作催化剂。当溶液的pH值大于7.O时，CPMVA膜也能维持其稳定性，它对pH值的依赖程度明显小于其无机物形式的膜(H_4AsMo_(11)VO_(40))对pH值的依赖程度。CPMVA膜对Br0_3-的还原表现出很好的电催化活性，催化电流与BrO_3~-的浓度的平方成正比。这种有很高稳定性的新类型杂多酸膜在催化剂领域中将有很广阔的应用前景。2．电化学STM研究吸附在金属表面的表面活性剂聚集体由于电位诱导引起的结构变化表面活性剂在表面的吸附已广泛地被用于限制电极表面的活性和稳定溶液中的胶体和纳米粒子，但是人们对表面活性剂在电极表面的结构和由于电位变化所引起的结构改变并不清楚。在这个工作中我们利用现场STM观察了电位控制下表面活性剂十二烷基磺酸钠(SDS)在Au(111)表面的吸附。STM图像显示通过控制电位SDS在Au(111)表面有一从半圆柱胶束单层向致密双层膜过渡的构象变化。我们也建立了SDS聚集体在Au(111)表面电位诱导结构变化的模型。就我们所知，这是第一次系统地研究表面活性剂聚集体在金属表面的电位诱导结构变化。3．在固体表面构筑有序的聚苯胺分子导线我们提出了一种新的通过分子设计构筑有序聚苯胺分子导线的新方法。首先，根据Saveant的方法我们在HOPG表面修饰上有序的4-氨基苯单层，然后溶液中的苯胺分子通过阶跃的方法被层层电聚合在4-氨基苯单层修饰的HOPG表面，形成有序的聚苯胺分子导线。FTIR-ERS和XPS结果证实HOPG表面上形成了聚苯胺。SPM图显示在HOPG表面的聚苯胺平面结构为有序的3~(1/2) * 3~(1/2) R 30°。小角X-射线反射结果表明聚苯胺分子导线是垂直站立在HOPG表面。电化学测量进一步表明聚苯胺分子导线的形成有利于加速电子传递速率。这种先分子设计后电聚合的方法可能会成为一类在固体表面制备有序导电聚合物分子导线的新方法。依据上一个实验，我们在金表面通过自组装的方法构筑了绝缘分子导线。我们选择β-环糊精(β-CD)作为包络4-氨基硫酚的理想主体分子。β-CD和4-氨基硫酚形成的包络物首先被自组装到Au表面，然后也通过阶跃的方法被层层电聚合在自组装膜修饰的Au表面，形成有序的聚苯胺分子导线。FTIR-ERS和XPS结果证实Au表面上形成了聚苯胺。低电流STM(LC-STM)图像表明在Au(111)表面的聚苯胺分子线为六角的二维有序，分子与分子之间的最相邻距离为15.5±0.5 A。这种先进行CD超分子自组装后电聚合的方法可能会成为一类制备导电聚合物绝缘分子导线的新方法。4．SPM研究在HOPG表面电化学合成的纳米材料我们通过脉冲恒电位方法从稀的苯胺酸性溶液(1mM苯胺 + 1 M HClO_4)在HOPG表面制备聚苯胺纳米颗粒。我们利用FTIR-ERS、XPS、TM-AFM手段来表征聚苯胺纳米颗粒的组成和结构。FTIR-ERS和XPS结果表明制得的聚苯胺纳米颗粒主要以亚胺形式存在。TM-AFM图像显示分散于HOPG表面的聚苯胺纳米颗粒的表面覆盖度约为10~(10)cm~(-2)。这些纳米颗粒都为圆盘型，直径为200到600埃，高度为10到30埃。这些纳米颗粒的大小随聚合电量由5.7 μC/cm~2增加到19.3 μC/cm~2而增大。我们提出了一种通过分子设计在HOPG表面制备金属纳米粒子的新方法。第一步，根据Saveant的方法我们在HOPG表面修饰上一个4-氨基苯单层。第二步，通过配位相互作用Ag~+能在4-氨基功能化的HOPG表面形成单层。第三步，通过脉冲恒电位方法我们就能在4-氨基苯功能化的HOPG制备Ag纳米颗粒。电化学测量证明了在HOPG表面上Ag纳米颗粒的形成。STM图像显示通过这种方法制得的Ag纳米颗粒的大小十分均一且在HOPG表面上的分散度很高。这种新方法可被广泛地用来在碳表面制备各种金属纳米粒子。