反射率对入射角扫描测定单轴晶体的折射率

通过分析波矢沿任意方向的单轴晶体的折射率,在光轴位于入射面内时,给出了入射光分别为s光和p光的反射率拟合函数。利用改进的反射率扫描仪,测量了CaCO3晶体的s光和p光反射率随入射角变化情况,由理论拟合获得单轴晶体的两个主折射率,分别为no=1.6559和ne=1.4851。这种方法不需要对样品进行加工,其精度达到0.0001。另外,对于晶体光轴未知的情况,采用改进的布儒斯特技术分别测出三个晶体表面的布儒斯特角,由此可以确定光轴的方向。

Nonpolarizing guided-mode resonance filter

A normal-incidence nonpolarizing guided-mode resonance filter is designed. There are two waveguide layers and one grating layer in the filter. By adjusting the distance between the two waveguide layers, the same resonance wavelength for both TE and TM polarization can be achieved. An antireflection design method is also used to decrease the sideband reflection of the filter. The results show that the filter has high reflection, more than 99.9% at 500 nm, and the FW-HMs of TE- and TM-polarized light are 2.16 and 0.15 nm, respectively. (C) 2009 Optical Society of America

Surface plasmon resonance transmission filters at 1053 nm based on metallic grating with narrow slit

Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the transmission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.

三氟拉嗪抑制钙-钙调素对白杄花粉管生长的调节

花粉管是种子植物受精过程中雄性生殖单位的载体，具有典型的极性顶端生长模式，因此成为研究细胞极性生长机理的理想模式体系。本研究以裸子植物白杄（Picea meyeri Rehd.et Wils）花粉为材料，并以对花粉萌发和花粉管生长起关键作用的Ca2+作为切入点，分析钙-钙调素在花粉萌发及花粉管极性生长中的作用，同时也为进一步探讨它们在其他植物细胞中的作用机理研究提供重要参考。 通过细胞化学定位证明，白杄花粉中含有丰富的游离钙离子和钙调素，在花粉管顶端呈现明显的梯度分布;钙调素特异拮抗剂三氟拉嗪（trifluoperazine，简称TFP）可以在钙离子存在的情况下与钙调素特异性结合，从而抑制钙-钙调素复合物对下游效应蛋白的激活。微摩尔浓度的TFP明显抑制白杄花粉萌发以及花粉管的生长，并导致大部分花粉管畸形生长。TFP处理后的花粉管（约80%以上）中游离钙离子梯度消失或梯度不明显，由此说明钙调素参与花粉管顶端游离钙离子梯度的维持。抑制剂处理显著影响钙调素在花粉管顶端的梯度分布模式，梯度落差明显减小。 应用鬼笔环肽标记花粉管微丝骨架表明，正常生长的花粉管中微丝骨架沿花粉管长轴平行的方向呈网络状分布，但是在花粉管顶端仅有杂乱的微丝片断分布;低浓度TFP处理之后，微丝骨架分布的方向性丧失并开始卷曲，花粉管顶端的微丝片断消失，高浓度TFP处理之后微丝骨架完全断裂，聚集成短粗的束状。FM4-64标记花粉管后发现，经TFP处理的花粉管顶端胞吞速度明显加快，最终染料集中分布在紧贴质膜下很小的区域内，同时胞吞过程加快主要表现在染料进入花粉管细胞的速度加快，而随后染料在细胞内的扩散速度并无明显变化。以酸性磷酸酶为标志的胞吐活性也显著下降。通过MitoTracker染色发现，TFP处理之后花粉管中线粒体的形态和分布都发生了显著变化;在电子显微镜下观察显示，抑制剂处理的花粉管中液泡化现象严重，线粒体膨大变形，其内嵴的结构遭到严重破坏，同时高尔基体和内质网的形态也都发生了不同程度的异常变化，另外线粒体和液泡还出现了类似于自体吞噬的现象。 在荧光显微镜下观察发现，在标准培养基中培养的花粉管经苯胺兰染色后，胼胝质分布于整根花粉管侧壁上，而顶端区域胼胝质分布却很少或不存在。但经TFP处理之后，在花粉管细胞壁的个别区域有胼胝质大量沉积，同时在花粉管中还出现能被苯胺兰特异染色的许多颗粒状物质。此时花粉管顶端细胞壁中的纤维素含量明显减少。以单克隆抗体JIM5、JIM7标记果胶质，在激光扫描共聚焦显微镜下观察发现，标准培养基中培养的花粉管，酸性果胶质分布于整根花粉管的侧壁中，但在其顶端的含量很低或不存在，与此相反，酯化果胶质只分布在花粉管的顶端;而经TFP处理的花粉管中，酸性果胶质均匀分布于花粉管细胞壁上，酯化果胶质仅出现在花粉管基部的细胞壁中。单克隆抗体LM2和LM6标记结果显示，正常生长的花粉管细胞壁中AGPs呈周期性的环状分布，TFP处理后AGPs仅仅分布在花粉管基部的细胞壁中。SDS-PAGE电泳分析显示，抑制剂处理之后花粉管细胞壁蛋白的表达也发生明显变化。由FT-IR分析进一步证实了上述两种果胶质及纤维素在花粉管顶端细胞壁中相对含量的变化趋势。 利用双向电泳技术分离花粉管全蛋白，结果发现正常生长和TFP处理后的花粉管的大部分蛋白斑点都处于pI 4-8以及分子量在14-97 KD的范围内，主要是一些中等分子量大小、微酸性和中性的蛋白类群。由软件分析显示，除其中76个蛋白外，大部分蛋白质的表达并未发生变化。将上述76个表达量发生变化的差异蛋白进行胶内酶解，并经ESI-MS/MS分析鉴定，以及质谱数据库搜索，最终鉴定出57个蛋白，其中23个表达量上调，其余34个表达量下调。根据其生物学功能可以分为碳水化合物及能量代谢、胁迫及防御反应、细胞扩展、信号转导等功能蛋白类群。经TFP处理后，花粉管中碳水化合物及能量代谢过程整体水平下降，氧化磷酸化水平减低，但是丙酮酸脱羧酶旁路代谢水平却略有上升。由此暗示，花粉管在生长停滞的环境条件下，该途径可作为能量供应的替代机制;参与转一碳单位反应的蛋白表达量普遍上调，参与细胞延展（如细胞骨架重构、细胞壁多糖合成）的蛋白表达量下调，此项研究结果与上述的细胞生物学分析结论基本一致。 综上所述，当钙调素蛋白功能受到抑制后，顶端游离钙离子浓度梯度消失同时胞质钙离子浓度显著升高;细胞代谢水平（糖酵解和三羧酸酸循环）整体下降，而可能通过丙酮酸脱羧酶旁路来维持最低限度的能量供应;同时花粉管微丝骨架发生解聚，花粉管细胞壁组成成分合成水平下降，细胞延展相关的能力减弱，最终导致花粉管生长的停滞。钙-钙调素信号存在于白杄花粉萌发和花粉管生长这一特定的细胞生物学事件中，并参与花粉管顶端游离钙离子梯度的维持和定向生长。

Phylogeny and zoogeography of the cyprinid genus Epalzeorhynchos Bleeker (Cyprinidae : Ostariophysi)

A total of 62 variable osteological and external characters was found among the five currently recognized species of Epalzeorhynchos. When the genera Crossocheilus and Paracrossocheilus are combined as the outgroup, only 30 of these characters can be polarized. This includes six autapomorphies. The remaining 24 polarized characters form a data matrix which yields a single, 26-step tree with a Consistency Index (CI) of 1 and a Retention Index (RI) of 1, The analysis was also performed on a combined dataset in which the 32 unpolarized characters (characters for which the combined outgroup was dimorphic) were added and coded as missing data (i.e., "?"), Analyzing this data matrix with all multistate characters ordered generates the same single most-parsimonious tree with a length of 63 steps, a CI of 0.98 and a RI of 0.97, When either Crossocheilus or Paracrossocheilus is used as the sole outgroup, the same single most-parsimonious tree is produced although the numbers of informative characters and some of the polarities differ. Evidence is presented to support the following hypotheses: (1) E, kalopterus + E, frenatus + E. bicolor + E. munensis form a monophyletic group; (2) E. frenatus + E, bicolor + E, munensis form a monophyletic group with E, kalopterus as its sister group; this speciation event is congruent with the predictions of vicariant speciation mode I; and (3) E. bicolor and E. munensis are sister groups, again congruent with vicariant speciation mode I, Evidence presented here also supports the zoogeographical hypothesis that the faunas of the Indochinese region and the Greater Sundas are more closely related to each other than either of them is to the lower Salween basin fauna and that the lower Mekong, Chao Phraya, and Mac Khlong basin faunas are more closely related to each other than any of them is to the Greater Sundas, In addition, the monophyly of Epalzeorhynchos is also preliminarily discussed by including either Paracrossocheilus or Crossocheilus in the ingroup. It is demonstrated that E. bicornis clusters with Paracrossocheilus when Paracrossocheilus is included in the ingroup. It seems likely that the taxonomic position of E. bicornis will be resolved as more fishes of the Crossocheilus group are included in future studies.

Rashba electron transport in one-dimensional quantum waveguides

The properties of Rashba wave function in the planar one-dimensional waveguide are studied, and the following results are obtained. Due to the Rashba effect, the plane waves of electron with the energy E divide into two kinds of waves with the wave vectors k(1)=k(0)+k(delta) and k(2)=k(0)-k(delta), where k(delta) is proportional to the Rashba coefficient, and their spin orientations are +pi/2 (spin up) and -pi/2 (spin down) with respect to the circuit, respectively. If there is gate or ferromagnetic contact in the circuit, the Rashba wave function becomes standing wave form exp(+/- ik(delta)l)sin[k(0)(l-L)], where L is the position coordinate of the gate or contact. Unlike the electron without considering the spin, the phase of the Rashba plane or standing wave function depends on the direction angle theta of the circuit. The travel velocity of the Rashba waves with the wave vector k(1) or k(2) are the same hk(0)/m*. The boundary conditions of the Rashba wave functions at the intersection of circuits are given from the continuity of wave functions and the conservation of current density. Using the boundary conditions of Rashba wave functions we study the transmission and reflection probabilities of Rashba electron moving in several structures, and find the interference effects of the two Rashba waves with different wave vectors caused by ferromagnetic contact or the gate. Lastly we derive the general theory of multiple branches structure. The theory can be used to design various spin polarized devices.

Ultrafast photo-induced turning of magnetization and its relaxation dynamics in GaMnAs

We report that, by linearly polarized pumping of different wavelengths, Kerr transients appear at zero magnetic field only in the case when GaMnAs samples are initialized at 3 K by first applying a 0.8 Tesla field and then returning to zero field. We find that, instead of magnetization precession, the near-band gap excitation induces a coherent out-of-plane turning of magnetization, which shows very long relaxation dynamics with no precession. When photon energy increases, the peak value of the Kerr transient increases, but it decays rapidly to the original slow transient seen under the near-band-gap excitation.

Design of a compact polarizing beam splitter based on a photonic crystal ring resonator with a triangular lattice

We propose and simulate a new kind of compact polarizing beam splitter (PBS) based on a photonic crystal ring resonator (PCRR) with complete photonic bandgaps. The two polarized states are separated far enough by resonant and nonresonant coupling between the waveguide modes and the microring modes. Some defect holes are utilized to control the beam propagation. The simulated results obtained by the finite-difference time-domain method show that high transmission (over 95%) is obtained and the polarization separation is realized with a length as short as 3.1 mu m. The design of the proposed PBS can be flexible, thanks to the advantages of PCRRs.

Enhanced mid-infrared transmission in heavily doped n-type semiconductor film based on surface plasmons

Transmission of electromagnetic wave in a heavily doped n-type GaAs film is studied theoretically. From the calculations, an extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies is found. This extraordinary transmission is attributed to the coupling of the surface-plasmon polariton modes and waveguide modes. By selecting a set of groove parameters, the transmission is optimized to a maximum. Furthermore, the transmission can be tuned by dopant concentrations. As the dopant concentration increases, the peak position shifts to higher frequency but the peak value decreases.

Microstructure and Optical Properties of Nonpolar m-Plane GaN Films Grown on m-Plane Sapphire by Hydride Vapor Phase Epitaxy

Thick nonpolar (10 (1) over bar0) GaN layers were grown on m-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) using magnetron sputtered ZnO buffers, while semipolar (10 (1) over bar(3) over bar) GaN layers were obtained by the conventional two-step growth method using the same substrate. The in-plane anisotropic structural characteristics and stress distribution of the epilayers were revealed by high. resolution X-ray diffraction and polarized Raman scattering measurements. Atomic force microscopy (AFM) images revealed that the striated surface morphologies correlated with the basal plane stacking faults for both (10 (1) over bar0) and (10 (1) over bar(3) over bar) GaN films. The m-plane GaN surface showed many triangular-shaped pits aligning uniformly with the tips pointing to the c-axis after etching in boiled KOH, whereas the oblique hillocks appeared on the semipolar epilayers. In addition, the dominant emission at 3.42eV in m-plane GaN films displayed a red shift with respect to that in semipolar epilayers, maybe owing to the different strain states present in the two epitaxial layers. [DOI: 10.1143/JJAP.47.3346]

Electronic structure and optical properties of GaN with Mn-doping

Calculations of the electronic structure and the density of states of GaN with Mn are carried out by means of first-principles plane-wave pesudopotential method based on density functional theory. The results reveal a 100% spin polarized impurity band in band structure of Ga1-xMnxN due to hybridization of Mn 3d and N 2p orbitals. The material is half metallic and suited for spin injectors. In addition, a peak of refractive index can be observed near the energy gap. The absorption coefficient increases in the UV region with the increase of the Mn content.

Design of a compact polarization beam splitter based on a deformed photonic crystal directional coupler

In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric (TE) guided mode and transverse-magnetic (TM) guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguides is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.5 mu m. A finite-difference time-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.

Electronic structure and optical gain of wurtzite ZnO nanowires

The electronic structure and optical gain of wurtzite ZnO nanowires are investigated in the framework of effective-mass envelope-function theory. We found that as the elliptical aspect ratio e increases to be larger than a critical value, the hole ground states may change from optically dark to optically bright. The optical gain of ZnO nanowires increases as the hole density increases. For elliptical wire with large e, the y-polarized mode gain can be several thousand cm(-1), while the x-poiarized mode gain may be 26 times smaller than the former, so they can be used as ultraviolet linearly polarized lasers. (C) 2008 American Institute of Physics.

Analytical model of spin filtering effect and its experimental verification in a forward-biased iron-metal-Al2O3-n-type GaAs tunneling structure under optical spin orientation

An analytical model for the spin filtering transport in a ferromagnetic-metal - Al2O3 - n-type semiconductor tunneling structure has been developed, and demonstrated that the ratio of the helicity-modulated photo-response to the chopped one is proportional to the sum of the relative asymmetry in conductance of two opposite spin-polarized tunneling channels and the MCD effect of the ferromagnetic metal film. The performed measurement in an iron-metal/Al2O3/n-type GaAs tunneling structure under the optical spin orientation has verified that all the aspects of the experimental results are very well in accordance with our model in the regime of the spin filtering. After the MCD effect of the iron film is calibrated by an independent measurement, the physical quantity of Delta G(t)/G(t) (Delta G(t) = G(t)(up arrow) - G(t)(down arrow) is the difference of the conductance between two opposite spin tunneling channels, G(t) =( G(t)(up arrow) + G(t)(down arrow))/2 the averaged tunneling conductance), which concerns us most, can be determined quantitatively with a high sensitivity in the framework of our analytical model. Copyright (c) EPLA, 2008.

Mid-infrared heavily n-doped GaAs extraordinary transmission through subwavelength grooves

Transmission of an electromagnetic wave from a heavily doped n-type GaAs film is studied theoretically. The calculations are performed using the two-dimensional finite-different time-domain method. From the calculations, we find the extraordinary transmission of p-polarized waves through the film with subwavelength grooves on both surfaces at mid-infrared frequencies. By determining a set of groove parameters, we optimize the transmission to as high as 55.2%. We ascribe this extraordinary transmission to the coupling of the surface-plasmon polariton modes and waveguide modes. Such an enhanced transmission device can be useful for mid-infrared wave filters, emitters, and monitors.