Multi-band giant circular dichroism based on conjugated bilayer twisted-semicircle nanostructure at optical frequency

Plasmonic circular dichroism (CD) effect has been drawn great attention increasingly for its wide application in the fields of bio-sensing, biological detection, pharmaceuticals, and analytical chemistry. In this paper, we propose a chiral metasurface (CMS) to achieve strong multi-band CD effect at optical frequency. The designed CMS is composed of a periodic array of conjugated bilayer twisted-semicircle nanostructures. The numerical simulation results show that the CMS can produce strong multi-band CD effect due to the different coupling resonance modes under the excitations of left-handed circular polarization (LCP) light and right-handed circular polarization (RCP) light. It is shown that the chiral-selective absorption peaks can reach 89.4% and 95% for LCP light, 79% and 78.2% for RCP light, and the maximum CD is about 0.69 and −0.61 at 198.75 THz and 352.25 THz, 0.69 and −0.54 at 291.75 THz and 402.25 THz, respectively. The mechanism of the giant CD effect of the CSM has been revealed by analyzing the coupling mode of electric dipoles on the top and bottom layer through surface current distributions. Furthermore, the geometric parameter dependences of CD effect in the proposed CMS have been also studied numerically. The present results will guide the design of plasmonic chiral nanostructures for enhancing the CD effect.     

Photoinduced anisotropic edge states and signatures of nonequilibrium spin polarization in silicene nanoribbons

Most topological phase transitions are accompanied by the emergence of surface/edge states with spin dependence. Usually, the quantized Hall conductivity cannot characterize the anisotropic transports and spin dependence of topological states. Here, we study the intricate topological phase transition and the anisotropic behavior of edge states in silicene nanoribbon submitted to an electric field or/and a light irradiation. It is interesting to find that a circularly polarized light can induce a type-II quantum anomaly Hall phase, which is manifested as the high Chern number and the strong anisotropic edge states. Besides the measurement of the quantized Hall conductivity, we further propose to probe these topological phase transitions and the anisotropy of edge states by measuring the current-induced nonequilibrium spin polarization. It is found that the spin polarization exhibits more signatures about the behavior of surface/edge states, beyond the quantized Hall conductivity, especially for spin-dependent transports with different velocities.     

The effect of two ferromagnetic metal stripes on valley polarization of electrons in a graphene

As the key factor for designing the valleytronic devices is to well understand the valley-dependent transport mechanism in graphene, we investigate, in this work, the effect of two ferromagnetic (FM) metal stripes on the valley polarization in a graphene nanostructure with a strain. The nearly 100% valley polarization is observed at certain energy windows and it can be easily controlled through changing the width and the position of the FM stripe as well as the strength of the magnetic field induced by the FM stripe. Our interesting findings reveal the valley-dependent transport mechanism of electrons and promote the realization of the new types of valleytronic devices modulated by the FM stripe and the strain.     

基于斜向背散射偏振拉曼光谱的{100}c-Si面内应力分析

复杂应力状态下应力分量的解耦分析对半导体的设计和制造具有重要意义。本文开展了方法学研究,首先建立了{100}晶面族单晶硅面内应力分量解耦分析模型,基于该模型,通过改变入射光和散射光的几何构型和偏振构型,可得到单晶硅拉曼频移与应力分量的解析关系。在此基础上,提出了一种利用斜向背散射偏振拉曼光谱在不同倾角、偏振方向和样品旋转角度下开展原位拉曼探测实现应力分量解耦分析的实用技术。本文通过实验验证了该方法的可靠性和适用性。     

TracePro在“光的偏振实验”中的应用

为提高光的偏振实验教学效果和教学质量,在教学中引入专业的光学设计软件--TracePro,利用该软件仿真了光的双折射过程和现象,以及偏振片的原理;建立光的偏振实验系统实体模型,完成光的偏振态判断实验;仿真光通过波片后的偏振态转换现象;验证马吕斯定律,并仿真了多层介质膜对光的分离和旋光现象.结果表明该方法可以提高教学效率,激发学生探索科学的主观能动性,仿真结论与理论推导和实际实验结果一致.     

The Influence of Signal Polarization on Quantum Bit Error Rate for Subcarrier Wave Quantum Key Distribution Protocol

In this paper, we consider the influence of a divergence of polarization of a quantum signal transmitted through an optical fiber channel on the quantum bit error rate of the subcarrier wave quantum key distribution protocol. Firstly, we investigate the dependence of the optical power of the signal on the modulation indices’ difference after the second phase modulation of the signal. Then we consider the Liouville equation with regard to relaxation in order to develop expressions of the dynamics of the Stokes parameters. As a result, we propose a model that describes quantum bit error rate for the subcarrier wave quantum key distribution depending on the characteristics of the optical fiber. Finally, we propose several methods for minimizing quantum bit error rate.     

Microstructure and dielectric study of pure BST and doped BSTF ceramic materials by broadband dielectric spectroscopy

Pure BST and doped BSTF (with BSTF2: Fe₂O₃ 2 wt % and BSTF4: Fe₂O₃ 4 wt %) ceramics were prepared by solid state reaction. XRD pattern showed the different phases were formed depend on the weight percent of Fe₂O₃. The crystal size and lattice parameters increased while the lattice strain decreased. The topography of the sintered samples shows increase of the grain size with increasing Fe₂O₃ ratio and hence enhances the compaction of ceramics. Broadband dielectric spectroscopy was employed to investigate the effect of magnetite nanoparticle on the dielectric properties of the pure BST ceramic. The interfacial polarization and the conductivity contribution reflect the high values of permittivity and its gradual increase as frequency decreases. The two BSTF samples show relaxation peak dynamic originated from presence of immobile species/electrons at low temperatures and defects/vacancies results from the formation of oxygen vacancies originates from the spontaneous change in oxidation states of Fe ions (Fe ^3+/Fe²⁺) at high temperatures. The relaxation rate obeys Arrhenius law at high temperatures in case of BST sample with activation energy 225 kJ/mol. This high value of activation energy at higher temperatures reflects and confirms the slowed down of the dynamics at the interphase and the decoupling nature of the OH-dynamic and the interfacial polarization.     

Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect

A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.     

Experimental review of the ϒ(1S, 2S, 3S) physics at e+e− colliders and the LHC

The three lowest-lying \mathrm{\Upsilon } states, i.e., \mathrm{\Upsilon }(1S), \mathrm{\Upsilon }(2S), and \mathrm{\Upsilon }(3S), composed of bb¯ pairs and below the BB ¯ threshold, provide a good platform for the researches of hadronic physics and physics beyond the Standard Model. They can be produced directly in e⁺e⁻ colliding experiments, such as CLEO, Babar, and Belle, with low continuum backgrounds. In these experiments, many measurements of the exclusive \mathrm{\Upsilon }(1S) and \mathrm{\Upsilon }(2S) decays into light hadrons, which shed light on the “80% rule” for the Okubo–Zweig–Iizuka suppressed decays in the bottomonium sector, were carried out. Meanwhile, many studies of the charmonium and bottomonium productions in \mathrm{\Upsilon }(1S, 2S, 3S) decays were performed, to distinguish different Quantum Chromodynamics (QCD) models. Besides, exotic states and new physics were also extensively explored in \mathrm{\Upsilon }(1S, 2S, 3S) decays at CLEO, BaBar, and Belle. The \mathrm{\Upsilon }(1S, 2S, 3S) states can also be produced in pp collisions and in collisions involving heavy ions. The precision measurements of their cross sections and polarizations at the large hadron collider (LHC), especially in the CMS, ATLAS, and LHCb experiments, help to understandΥproduction mechanisms in pp collisions. The observation of the sequentialΥsuppression in heavy ion collisions at CMS, LHCb, and ALICE is of great importance for verifying the quark–gluon plasma predicted by QCD. In this article, we review the experimental results on \mathrm{\Upsilon }(1S, 2S, 3S) at e⁺e⁻ colliders and the LHC, and summarize their prospects at Belle II and the LHC.     

随机介质背散射二维Mueller矩阵的数值模拟与分析

推导了随机介质背散射Mueller矩阵的直接计算公式,并运用矢量Monte Carlo方法进行了数值模拟.结果表明随机介质背散射二维Mueller矩阵方位关系随散射系数的减小而增强,而与微粒大小关系不大;Mueller矩阵元素绝对值的空间分布随径向呈近似指数规律衰减,矩阵元素的方位变化具有周期性.对称系统的二维Mueller矩阵的花样图中仅有7幅独立,其余9幅可通过对称、旋转变换得到.