Eigenfrequency Shift of Higher-Order Modes in a Coaxial Cavity with Eccentric Inner Rod

The eigenvalues of a coaxial cavity must be modified by the structural eccentricity (for instance, by the misalignment of the inner rod), which causes an eigenfrequency shift. In this paper the eigenfrequency shift of the higher-order modes is numerically investigated in terms of the eigenvalue equation. Taking the TE_{31, 17, 1}, TE_{32, 17, 1}, TE_{33, 17, 1} and TE_{34, 17, 1} modes as examples, calculations show that the eigenfrequency of a mode may have a down-shift or up-shift, which depends on the ratio of the outer conductor radius to the inner rod radius R _out/R _in. For a higher-order mode, the greater the value of R _out/R _in, the smaller the influence of the structural eccentricity on the eigenfrequency shift. Moreover, the structural eccentricity may have a weaker influence if the azimuthal index of the mode is higher.     

聚合物电光波导传播常数和损耗系数的微扰解

对于聚合物电光波导,依据理想光波导耦合理论的微扰理论,推导传播常数和损耗系数的近似表达式,从而将求解本征值的复杂复数运算简化成简单实数运算。数值计算表明,这些近似解与正确解很好相符。给出的近似公式和特征曲线可供聚合物电光波导及其器件的设计和制备作参考。     

渐变折射率波导传播特性微扰计算的代数递推公式

应用量子力学的超位力定理（HVT）和赫尔曼－费恩曼（Hellmann-Feynman）定理（HFT），导出了用微扰法计算渐变折射率平面波导传播常数各级近似值的代数递推公式，并给出了由传播常数近似值计算模场近似表达式的代数式。计算了几个典型实例，此法的特点是便于直接计算任意级近似的传播常数及模场分布，且可推广到二维波导的计算。     

二次多项式型平面光波导模式

用一级微扰理论，对二次多项式折射分布平面光波导，进行了波方程的解析求解，推得用Ａｉｒｙ函数表示的场解和色散方程。用一级微扰近似计算了传播常数，并与实验值进行了比较，其结果是符合的。     

矩形介质光波导的条形传递函数方法

将条形传递函数方法引入矩形介质光波导传播特性的分析计算,从标量波动方程的变分表达式出发,推导和建立了条形传递函数方法的基本方程和两种应用模型,作为算例,给出了阶跃型折射率分布矩形介质光波导的数值计算结果,并与其它方法进行了比较,表明了此方法的精度及对光波导问题的适用性。     

Ti∶LiNbO_3二维渐变折射率光波导传播常数的计算

从Ti∶LiNbO3波导截面折射率分布的特点出发，得出一套计算传播常数简单而精确的方法。文中对该法进行了分析，并应用该方法计算了钛扩散波导的色散关系。该方法为钛扩散光波导集成光学器件的设计提供了一种较可靠的理论手段。     

多层平面介质波导辐射模

介绍一种精确计算多层平面介质波导归一化正交辐射模的方法，在全辐射模的情况下，为了保证模的正交性，给出了准奇模和准偶模的确定方法，这此方法地计算机编程，为模传播法的建立和实际应用奠定了基础，本文最后给出几个应用的实例。     

强流环形电子束在同轴永磁Halbach结构磁路中传输的初步分析

利用有限元程序SUPERFISH计算求解了同轴永磁Halbach结构磁路的磁场, 并推导出该磁场位形磁感应强度各分量的近似表达式. 利用流体模型分析了作用在电子束上的力并导出了改进马丢方程形式的径向力平衡方程, 给出了平衡条件; 利用2.5维全电磁粒子模拟程序研究了强流环形电子束在该周期系统中传输的物理过程. 计算得出强流相对论电子束的稳定传输与电子束电流, 电子束厚度, 磁场强度, 电子束入射角度等因素有关. 分析认为利用同轴永磁Halbach结构磁路导引数KA的环形电子束, 并使之稳定传输是可能的. 同时该磁场聚焦形式也为Ubitron中的束--波相互作用提供了一个作用机制.     

Oscillating Guided Modes in Graphene-Based Asymmetric Waveguides

We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the structures of the guided modes are discussed under three distinct cases. For the cases of the classical motion and the Klein tunneling, the asymmetric structure does not influence the mode structures dramatically compared with that in the symmetric waveguide. But for the mixing case of the former two, the mode structures and the motion characteristics for the electron and the hole exhibit different behaviors at same condition. The results may be helpful for the practical application of graphene-based quantum devices.     

Oscillating Guided Modes in Graphene-Based Asymmetric Waveguides

We investigate the guided modes in monolayer graphene-based waveguides with asymmetric quantum well structure induced by unequal dc voltages. The dispersion relation for the guided modes is obtained analytically, the structures of the guided modes are discussed under three distinct cases. For the cases of the classical motion and the Klein tunneling, the asymmetric structure does not influence the mode structures dramatically compared with that in the symmetric waveguide. But for the mixing case of the former two, the mode structures and the motion characteristics for the electron and the hole exhibit different behaviors at same condition. The results may be helpful for the practical application of graphene-based quantum devices.     

Lognormal Modes of Dielectric Optical Waveguides

It is shown that, at a critical point where the effective refractive index of a mode coincides with the bulk index of a cladding region, optical waveguide modes exhibiting a lognormal feature are supportable for a hyperlongrange refractive-index profile. As a typical example of waveguides that support lognormal modes a parabolic-index core surrounded by a depressed-index cladding is presented.     

二次多项式折射率分布平面光波导的模式

对于折射率分布为二次多项式的非对称平面光波导,求解了Helmholtz方程,推得用抛物柱函数表示的模式场分布和模方程.结果可用于处理这类波导(如银离子交换玻璃光波导等)的模耦合或有关器件的问题.     

阵列波导传播常数的分析

在波导传输模中,涉及到一个基本的模式物理量传播常数。用紧束缚近似微扰法计算了阵列波导的传播常数与输入光角谱的关系,由此计算出传播常数的带宽。分析结果对器件的优化设计有一定的指导意义。     

Hybrid Modes in Highly Oversized Corrugated Rectangular Waveguides

Using a scattering matrix formalism the relative TE/TM eigenmode contents of hybrid modes in oversized corrugated rectangular waveguides has been calculated. The influences of slot depth and corrugation period on the eigenmode mixture have been examined.     

SOI及GeSi/Si脊形光波导的模式与波导几何结构

用有效折射率方法对SOI（绝缘体上硅）及GeSi/Si脊形光波导的单模条件进行了模拟,与Soref的单模条件进行了比较,将两者与实验结果进行了比较,得到了与实验结果符合得非常好的单模条件。同时对多模波导进行了模拟,得到了波导承载一阶和二阶模的条件。     

基于有限元的平面光波导粘接热应力分析

基于有限元理论对阵列光纤和波导芯片粘接情况进行了建模与仿真,分析了在温度变化下不同粘接区域厚度的热应力和微位移的产生和分布,结果表明粘接界面的边缘区域对温度变化最敏感.根据光弹效应定性分析了粘接区域的应力双折射,并利用光束传播法计算了由此微位移所导致的光功率损耗,结果表明若以附加损耗小于0.15 dB的标准考察,则必须要求粘胶厚度的理论值在16 μm以内.总结了温度变化和在相同条件下不同粘胶厚度对平面光波导封装性能的影响规律.     

内外开槽同轴潘尼管波导传播特性

推导了内外开槽同轴波导和外开槽圆波导的特征方程。数值模拟了内外开槽同轴波导及外开槽圆波导中2π模式的传播特性,研究了开槽深度与截止波数的关系及内外开槽潘尼管频率与各个半径之间的关系。结果表明：内外开槽同轴波导的特征值随内开槽深度的增加而增大,随外开槽深度的增加而减小;内槽半径对频率的影响很小,外槽半径起主要作用。     

复合结构偏心对同轴波导电磁特性的影响

采用三维电磁仿真软件CST Microwave Studio,数值模拟了内外导体轴线复合结构偏心对同轴波导电磁特性的影响。结果表明:当内外导体的轴线同时存在平行偏心和倾斜偏心时,改变了波导的边界条件,从而导致同轴波导的S21参数和电场幅值实质性下降。随着复合结构偏心程度的加剧,同轴波导的S21参数和电场幅值减小越大。同时,复合结构偏心比平行偏心或倾斜偏心单独存在时对同轴波导电磁性能的影响更大。因此,在同轴波导的实际制作过程中,应尽力避免发生复合结构偏心。     

聚合物脊形光波导TM模色散特性的偏振修正

有机聚合物脊形光波导的色散特性对聚合物光子学器件性能具有重要影响.本文利用标量变分理论计算脊形光波导的有效折射率,其用到的近似光场分布运用变分有效折射率法获得.考虑折射率分布的横向变化,基于导模满足的矢量波动方程,利用微扰法对标量变分理论所得有效折射率进行偏振修正,求得精度更高的色散特性.对聚合物多模脊形光波导基模和高阶模的色散特性进行分析,研究了波导结构参数对色散特性的影响,分析了单模波导TM、TE基模的偏振色散特性.研究结果表明,运用本征方程分析TM模的色散特性误差大,必须加以修正;而对于TE模,其误差相对较小.     

Gyrokinetic Analysis of Influence of Electron Beam Eccentricity on Operation of Higher-Order Mode in a Coaxial Cavity Gyrotron

A gyrokinetic analysis is presented to the influence of the electron beam eccentricity on the power and starting current of a coaxial cavity gyrotron, which operates in a higher-order mode TE_{31, 17, 1} with a frequency of 165 GHz. It is found that the starting current becomes larger because of the existence of the electron-beam eccentricity. Especially, the power will be decreased substantially by the electron beam eccentricity, for example, down to 93% of the power without any eccentricity even if the eccentricity is 1% of the outer conductor radius. The acceptable range of the electron beam voltage and operating magnetic field for the establishment of the electromagnetic oscillation is narrowed by the electron-beam eccentricity.