PPQ共轭有机聚合物平面光波导的非线性传输特性的实验研究

从实验上研究了聚苯基喹恶啉（ＰＰＱ）共轭有机物平面光波导中的飞秒光脉冲的非线性传输特性，难过研究其光波导中由于自相位调制效应而导致的光谱展宽，得到了ＰＰＱ的非线性折射率，同时表明ＰＰＱ共轭有机物平面光波导中具较大的非线性效应，有可能制作较理想的全光器件。     

Interferometric optical isolator with Si guiding layer fabricated by wafer bonding

An interferometric optical isolator, with a Si guiding layer, employing a nonreciprocal phase shift was studied. The optical isolator was comprised of a magneto-optic waveguide with a magnetic garnet/Si/SiO₂ structure, which was fabricated by wafer bonding technique. The nonreciprocal phase shift in the magneto-optic waveguide with the Si guiding layer was calculated at a wavelength of 1.55 μm. Several kinds of layer structures in the magneto-optic waveguide were discussed.     

Induced steepening of femtosecond pulses

The femtosecond pulse conversion to the XUV has been studied theoretically for the first time in a gas-filled waveguide, including the influence of the pump-induced phase modulation on the phase matching conditions, waveguide propagation and signal pulse shape. The conversion of femtosecond pulses from excimer amplifiers to the range of 83 nm to 88 nm is discussed     

Theoretical Study for Folded Waveguide Traveling Wave Tube

A wideband folded waveguide traveling-wave tube (TWT) amplifier has advantages of simpler coupling structures and robust structure over the conventional helix TWT. The phase velocity of waves in folded waveguide is slowed down to the velocity of electron beam. Slow-wave interaction with the electron beam in folded waveguide is studied in a linear fashion. For a cold beam, the linear theory predicts a gain of 2 dB/cm and a bandwidth of 37% at the center frequency of 14 GHz. A closed algebraic dispersion relation for the frequency and the axial phase shift per period is obtained using an equivalent circuit model. Numerical solution calculated from the dispersion relation and three-dimensional electromagnetic code, HFSS simulations predict a mode coalescing in the folded waveguide. And a theoretical phase velocity prediction of the electromagnetic wave in this circuit is verified by HFSS simulations.     

太赫兹波在有限电导率金属空芯波导中的传输特性

研究了太赫兹波在具有有限电导率的金属镀层空芯波导中的传输特性.从其传输的特性方程出发,利用Newton-Raphson迭代方法数值模拟了传输损耗和相位常数随太赫兹波频率、波导内径以及波导中金属镀层的电导率的变化关系.结果表明,采用大芯径波导和高电导率的金属镀层能有效降低太赫兹波的传输损耗. 关键词： 太赫兹波 空芯波导 特征方程     

基于手性声子晶体的谷拓扑声输运

研究手性风车形散射体构建的谷拓扑声波导。具有右手与左手手性风车形散射体的声子晶体具有截然不同的声谷拓扑特性。当两种手性风车形散射体从-60°旋转到60°时,其所构建的声子晶体均出现2次偶然简并的狄拉克点与谷霍尔相变。基于两种具有相反谷霍尔相的手性声子晶体构建的谷拓扑声波导,在其重叠体带隙内存在一对局域在波导分界面处的谷态边缘态。实验研究表明,该边缘态可以很好的支持谷拓扑声输运,且对弯曲与无序两种缺陷具有一定的鲁棒性.      

Analysis of a Metal-Coated Planar Dielectric Waveguide with Chiral Cladding

The propagation characteristics of a metal-coated planar waveguide with chiral media filled in the cladding are presented. The effects of chirality on cutoff, dispersion characteristics and field distributions of the waveguide are studied. The results show that cladding chirality brings phase chopping to the transverse electric field component of those modes with odd mode numbers.     

Nonlinear Phase Shift by Parametric Amplification in Leaky Waveguides

In this article, the cascaded second-order nonlinear phase shifts induced in the signal wave are studied using the three-wave parametric interaction in a four-layered QPM leaky waveguide configuration in Z-cut LiNbO 3 . In this interaction, the pump-andsignal waves are guided modes and the idler is radiated into the substrate. We have analyzed the nonlinear phase shifts induced in the signal wave due to cascaded second-order effects, as a function of different waveguide parameters. These studies should find application in realizing practical all-optical signal processing devices.     

Nonlinear Phase Shift by Parametric Amplification in Leaky Waveguides

In this article, the cascaded second-order nonlinear phase shifts induced in the signal wave are studied using the three-wave parametric interaction in a four-layered QPM leaky waveguide configuration in Z-cut LiNbO 3 . In this interaction, the pump-andsignal waves are guided modes and the idler is radiated into the substrate. We have analyzed the nonlinear phase shifts induced in the signal wave due to cascaded second-order effects, as a function of different waveguide parameters. These studies should find application in realizing practical all-optical signal processing devices.     

Computation of the tracking force acting on a relativistic electron beam propagating in a conducting waveguide under the ohmic and ion-focused regimes

The force of interaction between a relativistic electron beam deflected by resistive hose instability and the eddy current induced in a tubular plasma channel of finite conductivity is computed. Dependences of the force on channel ohmic conductivity and current rise time in a beam pulse are studied. For a beam propagating through a perfectly conducting waveguide under the ion-focused regime, the interaction of the beam with the ion-channel electrostatic image on the waveguide wall is studied for the case when the beam and the channel are deflected from the waveguide axis as a result of ion hose instability. The dependence of the force on both deflection amplitudes is ascertained for the nonlinear phase of instability. It is demonstrated that the force under study may become comparable to the beam-channel interaction force if the deflections are large.     

AWG中波导间耦合造成的相位畸变的分析

用(1,1)阶Pad啨近似的广角BPM计算了阵列波导光栅(AWG)中由于阵列波导间耦合造成的相位畸变以及由于相位畸变引起的相位误差分别考虑了光从中心/非中心输入波导入射两种情况结果表明,波导间的耦合会造成显著的相位畸变,但由此引起的相位误差却很小,光从中心输入波导入射时对应的相位误差10-3rad,从非中心输入波导入射时的相位误差约为10-2rad针对波导阵列边缘效应引起的相位畸变,设计AWG结构时,在阵列部分两侧增加了边缘辅助波导结构,从而消除了边缘效应,使得边缘阵列波导对应的相位误差从10-1rad量级减小为10-3(10-2)rad量级.     

A Simple and Effective Method for Calculating the Bending Loss and Phase Enhancement of a Bent Planar Waveguide

A simple and effective method is introduced to calculate the bending loss and phase enhancement of a bent planar waveguide. The wave field is represented in terms of Airy functions and an eigenvalue equation is derived by matching the boundary conditions and the radiation condition in the outer cladding layer. The complex propagation constant is obtained by solving the eigenvalue equation with the Newton-Raphson method, and the imaginary part of the propagation constant gives directly the bending loss of the bent waveguide. The results are compared with the previous experimental and numerical results and are shown to be highly accurate and effective. The phase enhancement due to the bending is also studied.     

Nanofocusing of terahertz wave on conical metal wire waveguides

The nanofocusing of the terahertz (THz) radiation energy is studied. By using a conical metal nanowire waveguide, we focus the energy of the terahertz surface plasmon polaritons (THz SPPs) to several nanometers’ scale. Another interesting property of the THz SPPs propagation on the waveguide is that the peak electric field at the waveguide tip enhances many times. What is more, both the phase velocity and the attenuation coefficient versus the wire radius are obtained. The terahertz energy nanofocusing opens the way to observe terahertz propagating and imaging on the nanoscale.     

The use of effective phase velocity to decrease the direction finding error for a low-frequency signal in a waveguide

The mode, interference, and phase structures of the low-frequency sound field and the spatial responses of the extended linear array in a waveguide are studied. The wide-angle parabolic approximation and the normal mode method are used to perform calculations. A possibility of approximating the field in the zone of interference maxima by the equivalent plane wave model with the real amplitude and averaged effective phase velocity (EPV) calculated or measured from the phase gradient at the array aperture is investigated. The use of EPV in the zone of interference maxima is shown to decrease substantially the direction finding error. The conclusion is drawn that the array and the transfer function of the waveguide can be approximately matched if the speed of sound in water is substituted with the EPV in the bearing algorithm.     

一种高功率微波金属片波导移相器设计与特性分析

设计了一种高功率微波矩形波导移相器,在矩形波导中平行于电场放置金属片,沿波导宽边移动金属片,实现波导内的可变相移。通过优化设计波导和金属片的结构尺寸可实现0~360°相移,通过优化设计金属片过渡匹配结构可实现较低的插损。设计波导内为全金属结构,不存在介质材料,采用真空绝缘可以承受较高的功率传输。设计了中心频率为9.4GHz的金属片波导移相器,移相器最大插损小于0.2dB,功率容量设计达到64 MW。实验测试,移相器最大插损小于0.5dB,相频曲线呈线性关系。     

Generation of a sequence of frequency-modulated pulses in longitudinally inhomogeneous optical waveguides

The conditions for the generation and efficient amplification of frequency-modulated soliton-like wave packets in longitudinally inhomogeneous active optical waveguides have been studied. The possibility of forming a sequence of pico- and subpicosecond pulses from quasi-continuous radiation in active and passive optical waveguides with the group-velocity dispersion (GVD) changing over the waveguide length is considered. The behavior of a wave packet in the well-developed phase of modulation instability with a change in the waveguide inhomogeneity parameters has been investigated based on the numerical analysis.     

94 GHz回旋管过模波导模式转换与传输

 在耦合波理论的基础上,研究了94 GHz回旋管内置TE₀₃-TE₀₂-TE₀₁模式转换器和外接的TE₀₁-TE₁₁模式转换器。采用半径渐变微扰和轴线微扰几何结构以及不同的相位重匹配技术进行优化分析,得到了可靠的最优几何参量,设计出了紧凑、高效的94 GHz波纹波导模式转换器和蛇形线模式转换器。回旋管的热测实验中测出的模式样图表明,所设计的内置模式变换器有效地实现了TE₀₃-TE₀₂-TE₀₁的模式转换。     

Nondestructive measurement of loss performance in channel waveguide devices with phase modulator

A novel method using a phase modulator is proposed for the nondestructive measurement of propagation loss in a channel waveguide. The phase modulator was fabricated on a Ti-diffused LiNbO3 crystal. Tuning the effective optical length of a waveguide by application of an electrical field on the phase modulator, the contrast of the resultant Fabry-Perot resonator in a channel waveguide device can be measured. The associated propagation attenuation coefficients are determined from the experimental results. Coordination of the phase modulator with an optical channel waveguide device not only allows measurement of the bending loss, but improvement in the relative intensity noise owing to the reduction of the reflected power.     

相匹配契伦可夫辐射式倍频

用波导产生倍频波时,如果倍频波进入辐射模区,仍然有相匹配问题。契伦可夫辐射式倍频不是自动地实现相匹配的。相匹配要求导波基波模式场,倍频传输场(自由波),倍频触发场,以及经多次反射透射后的辐射场的迭加形成的总辐射场处于同步的相匹配状态。根据这个相匹配的分析,提出波导契伦可夫相匹配的特有的方法,那就是对波导的模色散进行设计,并指出非对称波导的特有优点,是改变一个边界上的反射相变,即选择不同色散的线性材料作包层,由此可得到相匹配的高效契伦可夫倍频辐射。     

Modeling of a bimetallic eccentric cylindrical plasma waveguide based on a transmission line for TEM-mode

In this paper, a plasma waveguide made of two eccentric cylindrical metallic walls have been studied according to the theory of transmission lines. The inductance per unit length L, the capacitance per unit length C, the resistance per unit length R and the shunt conductance per unit length G are obtained. The graphs of variations of the mentioned parameters vs. geometrical dimensions of waveguide are investigated. This investigations have been done for two different types of plasma waveguide. At first stage, plasma region will be considered in cold and collisional approximation and in second stage, a drift plasma in cold collisionless approximation will be considered. Also, graphs of phase velocity variation vs. the main parameters of the waveguide are presented.