Theoretical study of photon emission from single quantum dot emitter coupled to surface plasmons

Motivated by the recent pioneering advances on nanoscale plasmonics and also nanophotonics technology based on the surface plasmons (SPs), in this work, we give a master equation model in the Lindblad form and investigate the quantum optical properties of single quantum dot (QD) emitter coupled to the SPs of a metallic nanowire. Our main results demonstrate the QD luminescence results of photon emission show three distinctive regimes depending on the distance between QD and metallic nanowire, which elucidates a crossover passing from being metallic dissipative for much smaller emitter-nanowire distances to surface plasmon (SP) emission for larger separations at the vicinity of plasmonic metallic nanowire. Besides, our results also indicate that, for both the resonant case and the detuning case, through measuring QD emitter luminescence spectra and second-order correlation functions, the information about the QD emitter coupling to the SPs of the dissipative metallic nanowire can be extracted. This theoretical study will serve as an introduction to understanding the nanoplasmonic imaging spectroscopy and pave a new way to realize the quantum information devices.     

一维金属光栅的光学反射吸收

利用RCWA(rigid coupled-wave analysis)方法研究了一维金属光栅的反射特性,考察了 瑞利反常、表面等离激元驻波共振和几何共振三种共振吸收机理,分析了这三种机理的相互作用,如表面等离激元驻波共振和几何共振可以形成混合模式. 在反射式复合金属光栅中,确认了第四种共振形式,即相位共振. 数值计算表明相位共振对光学吸收的影响有两种形式: 当光栅周期大于一个波长时,相位共振导致尖锐的吸收峰,峰位在几何共振吸收峰一侧;当光栅周期小于一个波长时,相位共振导致混合模式的共振吸收峰发生劈裂. 对一维金属光栅反射特性的研究增加了对金属光栅共振吸收模式及其相互作用的认识. 关键词： 一维金属光栅 瑞利反常 表面等离激元 相位共振     

Frequency dispersive complex permittivity and permeability of ferromagnetic metallic granular composite at microwave frequencies

We experimentally studied the frequency dependent complex permittivity ε and permeability μ of composite composed of carbonyl iron powder (CIP) and epoxy resin in the frequency range 1-18 GHz. We found that the intrinsic ε and μ of CIP extracted from the measured ε and μ of composites follow the classical Maxwell equations and the Landau-Lifshitz-Gilbert (LLG) equation, respectively. The dependences of ε and μ of composites on the volume fraction of CIP (vf_CIP) were investigated using the two-exponent phenomenological percolation equation (TEPPE). We found that the TEPPE can fit the experimental results very well. Comparing the results of percolation parameters derived by experimental data at different frequencies, we show that the TEPPE is frequency independent for the composites at microwave frequencies. The results also show that the ε and μ spectrums of composites with definite vf_CIP can be correctly calculated by combining the TEPPE with the theoretical models of intrinsic ε and μ.     

Sensitive determination of diuron on zinc oxide nanoparticles modified carbon paste electrode in soil and water samples

An electrochemical sensor based on Zinc oxide nanoparticles (ZnONPs) modified carbon paste electrode was designed for the toxic diuron pesticide detection. The ZnONPs were synthesized through the hydrothermal route and their structural properties were investigated via scanning electron microscopy (SEM) and X-ray diffraction powder (XRD). The designed ZnONPs-modified carbon paste electrode (ZnONPs-CPE) was characterized using cyclic voltammetry and electrochemical impedance spectroscopy. The sensor showed significantly enhanced sensitivity on the diuron oxidation peak current, compared to the bare carbon paste electrode. Qualitative and quantitative analysis were performed using cyclic voltammetry (CV) and square wave voltammetry (SWV). Experimental parameters such as pH, amount of ZnONPs and frequency were evaluated and the optimized conditions were obtained with 0.1 M phosphate buffer solution at pH=8, a frequency of 50 Hz and a quantity of 5 mg of ZnONPs. Under these conditions, linear responses ranging from 1.3 to 7.7 μM and 8.6 to 30 μM of diuron were obtained, with correlation coefficients of R²=0.994 and 0.996 respectively. Detection and quantification limits of 0.22 μM and 0.84 μM (S/N=3) were respectively achieved based on the 3σ method. The interference of some ions on the oxidation peak of diuron on ZnONPs-CPE was also evaluated and no interference was observed, therefore demonstrating the selectivity of the sensor. The proposed sensor, designed with ecofriendly materials, is sensitive, selective and was effectively used for diuron determination in soils and water samples with recoveries ranging from 98 % to 101.5 %.     

基于圆微带天线阵的射频涡旋电磁波的产生

射频涡旋电磁波等相位面呈涡旋状,是一种携有新自由度-轨道角动量的电磁波。在轨道角动量模式理论分析的基础上,提出了在中心频率6 GHz处产生携有轨道角动量的涡旋电磁波的一种圆微带天线阵新结构,设计了以双层圆形微带天线为阵元组成的圆形阵列天线,通过控制馈源的相位差,得到模式量子数为0,1,2, 3, 4的轨道角动量。仿真结果表明：携轨道角动量的电磁波矢量电场图具有涡旋波阵面的特性,合适的阵列半径和馈线排列分布将产生携有良好轨道角动量特性的涡旋电磁波,而不当的阵列半径或馈线排列分布将出现能量的分散或者相互耦合的问题。     

New MgLi based Mg-Li-Cu-(Y, Gd) BMGs: Preparation, glass forming ability and mechanical properties

Through calculating the forming enthalpy by Modified Miedema Model, new MgLi-based bulk amorphous alloys Mg-Li-Cu-(Y, Gd) have been successfully designed and fabricated by conventional copper mold injection casting method. The X-ray diffractometer and differential scanning calorimeter results indicated that the as-cast Mg-Li-Cu-(Y, Gd) alloys were fully amorphous structure after casting to critical diameter as large as 4 mm and 2 mm. The experimental results also proved that with increasing Li content (3 at.%-8 at.%), the supercooled liquid region temperature of Mg-Li-Cu-(Y, Gd) alloys gradually decreased accompanying the reduce of glass forming ability. It was also found that appropriate addition of metal Li effectively increased the fracture strength and elastic strain and reduced their corresponding densities. The maximal fracture strength reached 468 MPa and 478 MPa, respectively, which were much higher than normal MgLi-based crystalline alloys (~ 300 MPa).     

The Resonant Wave Numbers of Eccentric Ring Microstrip Antennas for All Modes

The method, connected with the concentric ring microstrip antenna and based on the perturbation , for the resonant wave numbers of eccentric ring microstrip antennas for all modes is suggested. The usefulness and accuracy of the method is shown through the comparison of the calculation used here with the measurement and other method from the reference.     

组合振子天线磁偶特性实验研究

通过对组合振子的实验研究,验证了磁偶极子回路所具有的优势：能够极大地改善天线低频传输以及辐射特性,具有明显的低频补偿能力。此外,通过设置磁偶回路周长比,比较了不同磁偶回路状态下的天线特性,发现双磁偶回路对于低频特性的改善要优于单磁偶回路,后者的优势主要体现在高频。根据这一现象,采用单磁偶回路结构设计工作频带为300 MHz~5 GHz组合振子接收天线。     

卵形钢弹对铝合金靶板侵彻问题的数值模拟

 基于球形空穴膨胀理论（SCE）,采用ABAQUS有限元商业软件并结合其子程序的二次开发功能对钢弹侵彻金属靶进行3D有限元数值模拟。根据空穴膨胀理论,靶体对侵彻弹体的影响可以用一个作用在弹体表面的力函数代替,这样在进行数值模拟时就无须划分靶体网格,也避免了复杂的接触问题,从而使模拟大大简化。模拟所用卵形弹为VAR 4340钢弹,靶体为6061-T6511铝合金。模拟过程中考虑到弹体的可变形性和入射时的微小偏航角等实际情况,并且考虑到了弹身在运动过程中和靶体的接触分离效应。所得模拟结果与文献中的实验结果进行了比较,发现模拟结果与实验结果吻合得很好,并得到了一些有意义的推论。     

Electromagnetic coupling reduction in dual-band microstrip antenna array using ultra-compact single-negative electric metamaterials for MIMO application

In this paper, an ultra-compact single negative(SNG) electric waveguided metamaterial(WG-MTM) is first investigated and used to reduce the mutual coupling in E H planes of a dual-band microstrip antenna array. The proposed SNG electric WG-MTM unit cell is designed by etching two different symmetrical spiral lines on the ground, and has two stopbands operating at 1.86 GHz and 2.40 GHz. The circuit size is very compact, which is only λ_0/33.6 ×λ_0/15.1(where λ_0 is the wavelength at 1.86 GHz in free space). Taking advantage of the dual-stopband property of the proposed SNG electric WG-MTM, a dual-band microstrip antenna array operating at 1.86 GHz and 2.40 GHz with very low mutual coupling is designed by embedding a cross shaped array of the proposed SNG electric WG-MTM. The measured and simulated results of the designed dual-band antenna array are in good agreement with each other, indicating that the mutual coupling of the fabricated dual-band antenna array realizes 9.8/11.1 d B reductions in the H plane, 8.5/7.9 d B reductions in the E plane at1.86 GHz and 2.40 GHz, respectively. Besides, the distance of the antenna elements in the array is only 0.35 λ_0(where λ_0 is the wavelength at 1.86 GHz in free space). The proposed strategy is used for the first time to reduce the mutual coupling in E H planes of the dual-band microstrip antenna array by using ultra-compact SNG electric WG-MTM.