Landau damping in a bounded magnetized plasma column

The damping decrement of Landau damping and the effect of thermal velocity on the frequency spectrum of a propagating wave in a bounded plasma column are investigated.The magnetized plasma column partially filling a cylindrical metallic tube is considered to be collisionless and non-degenerate.The Landau damping is due to the thermal motion of charge carriers and appears whenever the phase velocity of the plasma waves exceeds the thermal velocity of carriers.The analysis is based on a self-consistent kinetic theory and the solutions of the wave equation in a cylindrical plasma waveguide are presented using Vlasov and Maxwell equations.The hybrid mode dispersion equation for the cylindrical plasma waveguide is obtained through the application of appropriate boundary conditions to the plasma-vacuum interface.The dependence of Landau damping on plasma parameters and the effects of the metallic tube boundary on the dispersion characteristics of plasma and waveguide modes are investigated in detail through numerical calculations.     

Higher-order Dirac solitons in binary waveguide arrays

We study optical analogues of higher-order Dirac solitons (HODSs) in binary waveguide arrays. Like higher-order solitons obtained from the well-known nonlinear Schrödinger equation governing the pulse propagation in an optical fiber, these HODSs have amplitude profiles which are numerically shown to be periodic over large propagation distances. At the same time, HODSs possess some unique features. Firstly, the period of a HODS depends on its order parameter. Secondly, the discrete nature in binary waveguide arrays imposes the upper limit on the order parameter of HODSs. Thirdly, the order parameter of HODSs can vary continuously in a certain range.     

硅基槽式微环谐振腔型偏振解复用器全矢量分析

提出一种紧凑型偏振解复用器, 其中两条常规硅基波导作为输入/输出信号通道, 居于其中的槽式微环谐振腔用于偏振态/波长选择组件. 采用全矢量频域有限差分法详细分析了硅基常规及槽波导的模式特性, 结果发现其横磁模的模场布及其有效折射率相似, 而其横电模相应的特性则差异明显, 结果输入横磁模能够在谐振工作波长下从下路端口输出, 而输入横电模与微环耦合可以忽略, 直接从直通端口输出, 从而实现两偏振态的高效分离. 采用全矢量时域有限差分法详细分析了该偏振解复用器的光波传输特性, 结果表明, 当微环半径为3.489 μm时, 在1.55 μm工作波长下, 横磁模与横电模的消光比与插入损耗分别为 ～ 26.12 (36.67) dB与 ～ 0.49 (0.09) dB. 另外, 论文详细讨论了器件关键结构参数的制作容差, 并给出了输入模场在器件中的传输演变情况.     

浅海波导界面对点源振速方向的影响

采用“虚源法”分析计算了浅海波导环境中接收点处点源总振速方向与水平面夹角,侧重讨论确定性界面反射对总振速方向的影响。研究结果表明：总振速方向和接收点与声源的水平距离、两者深度,海底、海面特性以及声速剖面等有关。在等声速均匀浅海波导中,由于确定性界面反射的影响,当直达声掠射角为1°～50°时,合成总振速方向偏离直达声方向达1.5°～10.5°,声速剖面呈负梯度时,偏离程度更甚.     

过模矩形波导中硅芯片与基模亚毫米波的作用

模拟研究了过模矩形波导WR10中n型硅探测芯片对TE10模亚毫米波的响应。针对过模波导WR10中内置n型硅芯片的亚毫米波探测结构,推导了基模工作时的灵敏度表达式。采用三维电磁场时域有限差分方法,模拟计算了过模波导中300～400GHz频带的TE10模亚毫米波与硅芯片的相互作用,分析了探测结构中电压驻波比和芯片内平均电场随硅芯片参数变化的规律。结果表明,在相同的芯片参数下,过模探测结构并不影响电压驻波比和芯片内平均电场的大小,但两者随频率变化的波动程度增大。在300～400GHz工作频带内,优化得到了性能较优的过模探测结构,其电压驻波比不大于2.75(335～380GHz频带内不大于1.8),线性工作区的相对灵敏度约为0.127kW-1,频率响应的波动范围在±20.5%内,最大承受功率约为0.53kW,响应时间为100ps量级,满足亚毫米波大功率脉冲的直接探测需求。     

Monte Carlo Study of Slot-waveguide Liquid Crystal Phase Shifters

Abstract

We present detailed Monte Carlo simulations of a simple model of a nematic liquid crystal slot waveguide shifter, investigating the effect of an applied electric external field. The simulations are based on the Lebwohl-Lasher lattice spin model with boundary conditions chosen to mimic the planar alignment as in Silicon Organic Hybrid waveguides and the homeotropic anchoring appropriate for Polydimethylsiloxane polymer walls. The external field is modeled by adding a term to the Hamiltonian which describes its coupling to the mesogenic molecules. We have investigated the effect of the external field on the optical transmission and the ordering across the cell.     

Propagating surface plasmon polaritons for remote excitation surface-enhanced Raman scattering spectroscopy

To illustrate the attractive potentials of remote-excitation surface enhanced Raman scattering (RE-SERS), we review the fundamental concepts and typical applications of propagating surface plasmon polaritons (PSPPs). Based on the RE-SERS technic, the adsorbed molecules are protected from being directly illuminated, while the merits of SERS still remained. However, the critical limitations of applying RE-SERS hinder its rapid development. Hence, drawing an overview about the PSPPs would be beneficial for further promoting the significance of RE-SERS in biological application and investigating the mechanism of surface catalytic reactions.     

Accurate Measurement of a Small Defect in a Planar Waveguide

Abstract

A non-destructive test method of a small defect (a dust particle or an air bubble) in a strongly confined planar waveguide is demonstrated in this work. Based on strong resonances between the small defect and some special incident wavelengths, an accurate reconstruction of the defect parameters can quickly be obtained from our previous numerical method. An example is given to verify the validity of the present measurement method.     

Elastic Organic Crystals Based on Barbituric Derivative: Multi-faceted Bending and Flexible Optical Waveguide

Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT , which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH₃OH (v/v=2/8). Upon applying or removing the mechanical force, both the (100) and (040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28±0.01 GPa and 4.56±0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (C−H⋅⋅⋅π and C−H⋅⋅⋅C), H-bond (C−H⋅⋅⋅O) and π⋅⋅⋅π interactions between molecules were responsible for the generation of the crystal elasticity. Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm⁻¹ (straight state) and 0.9 dBmm⁻¹ (bent state), while the optical loss coefficient (α) were 1.5 dBmm⁻¹ (straight state) and 1.8 dBmm⁻¹ (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices.