Renormalization Effects in the Spectrum of a Coherently Driven Exciton–Biexciton System

Starting from the total Hamiltonian of an excited exciton–biexciton system, nonresonant renormalizations in the electronic spectrum of a coherently driven direct semiconductor are considered. Stringent group-theoretical inclusion of the particle spin in the Hamiltonian allows one to account for the dependence of different renormalization effects on polarizations of the incident laser fields. On the example of circularly polarized driving and probing pulses it is shown that the kind of observed renormalization is defined by the pump-and-probe polarization geometry. Thus, the exciton optical Stark effect must appear in the case of co-circular pump-and-probe, whereas a mixing of the polariton and biexciton spectra is possible only in the case of counter-circular pump-and-probe. The polariton--biexciton dispersion renormalization may manifest itself as synchronous splittings of the exciton--polariton and biexciton spectra under resonant pumping at a frequency of the polariton--biexciton transition, or in their shifts in opposite directions under near-resonant pumping. The mechanisms of both kinds of renormalization effects are analyzed, and the dependence of their characteristics on the pump parameters and microscopic parameters of the exciton–biexciton–photon system is established. An evaluation of the characteristics shows that the effect of polariton–biexciton dispersion renormalization dominates in the spectra of semiconductors with stable biexciton formation. Results of the theoretical study provide an adequate explanation of available experimental data.     

锥形光纤的偏振特性

随着光通信技术的不断发展，光纤的应用越来越广泛，而锥形光纤以其独特的传光方式越来越多地应用于光纤连接、成像及测量等领域。实验测定了不同锥角和不同长度锥形光纤的偏振特性。理论上，根据麦克斯韦方程组以及边界条件给出了光在理想光纤中的场分布，阐明了实际光纤中光的传输特性。论证了锥形光纤长度与其偏振特性的关系，进而利用几何光学方法对锥形光纤锥角与其偏振特性的关系作了定性说明。并用具体数据进行了定量计算，得出偏振光经锥形光纤传输或耦合后再传输到其终端所得到均是椭圆偏振光的结论。     

Simulation of polarization effects in AlGaN/GaN heterojunction

Because of their large band-gap, large high-field electron velocity, large breakdownfield, and large thermal conductivity, GaN and its heterojunction with AlGaN and InGaNhave foreseeable potential in the applications of high-power/temperature electronics, andoptoelectronic devices operative in UV and visible wavelength. Polarization inducedelectric field can reach the magnitude of ~MV/cm[1,2]. For AlGaN/GaN based FETs theconcentration of sheet carrier induced by polarization in the cha…     

复合型铁氧体全极化器

应用耦合波理论 ,对有两组NS/N′S′四磁极磁化铁氧体中极化传输进行了分析 .在X、S波段对多种椭圆极化进行了测试 ,还完成了 0°～ 180°范围内多种线极化波测试 .最后对全极化器应用作了简单介绍 .     

激光水下偏振特性用于目标图像探测

利用激光水下偏振特性获得偏振差分图像(PDI),并运用PDI技术,从理论和实验上对水下目标探测进行了研究.介绍了PDI基本概念和实验系统原理,然后比较分析了不同条件下普通图像与PDI在辨别目标距离及其纹理上的差别和PDI中背景偏振光的影响,得出利用目标和背景偏振光的差异区分二者,从而提高探测距离的结论,并取得了较好的效果.在此基础上提出了通过处理有关PDI偏振参量来进一步辨别目标与背景的设想.     

Polarization Sensitive Spectral Interferometric Optical Coherence Tomography for Biological Samples

A spectral interferometric optical coherence tomography (OCT) system which has polarization sensitivity is developed. This system reduces the mechanical scanning dimension by employing the principle of spectral interferometry, and measures a two dimensional cross-sectional image of biological tissue with one dimensional mechanical scanning. Sixteen OCT images with different polarization conditions are measured, and two dimensional distributions of each element of the Müller matrix of a sample to be measured are calculated.     

北京同步辐射装置3B1B生物光谱实验站

本文介绍北京同步辐射装置（ＢＳＲＦ）３Ｂ１Ｂ光束线、生物光谱实验站和圆二色谱仪的基本情况。报道北京正负电子对撞机（ＢＥＰＣ）同步辐射专用光期间，我们在站测量了１１种手征性生物和药物样品的圆二色（ＣＤ）谱，首次在国内利用同步辐射光获取了Ｄ－苯丙氨酸等样品的ＣＤ谱和Ｄ－及Ｌ－亮氨酸对称的ＣＤ曲线。     

Holographic image subtraction using a polarization technique

A holographic image subtraction technique is proposed. The vector nature of light is utilized in introducing a phase difference of π between the two reconstructed object waves. The experimental results are also presented.     

Circular dichroism and theoretical studies on the inclusion of the antimalarian drug Licochalcone-A in β-cyclodextrin

The Induced Circular Dichroism of the complex formed by inclusion of Licochalcone-A (a powerful antimalarian of natural origin) and β-cyclodextrin was measured and calculated. The association constant was determined by titration experiments of ICD and fluorescence. The lowest energy conformations of the complex were obtained through docking procedures and their Circular Dichroism was evaluated within the Tinoco framework. The geometry of the complex was found to be consistent with the main experimental features.     

Antiplane time-harmonic green’s functions for a circular inhomogeneity with an imperfect interface

Two-dimensional antiplane time-harmonic Green’s functions for a circular inhomogeneity with an imperfect interface are derived. Here the linear spring model with vanishing thickness is employed to characterize the imperfect interface. Explicit expressions for the displacement and the stress fields induced by time-harmonic antiplane line forces located both in the unbounded matrix and in the circular inhomogeneity are presented. When the circular frequency approaches zero, our results reduce to those for the static case. Numerical results are presented to show the influence of the frequency and the imperfection of the interface on the stress and displacement fields.