电子注对谐振腔中TM模式谐振频率和电磁场分布的影响

将电子注视为等离子体柱,从填充等离子体柱的谐振腔的物理模型出发,推导了圆柱腔填充中心电子注时TM0m0模式的特征方程,并重点分析了填充电子注的圆柱腔中TM010模式和TM020模式的谐振频率和电磁场分布随等离子频率的变化情况。研究结果表明,随着电子注的等离子体频率不断增大,谐振频率也不断增大,谐振腔内电场和磁场的分布也随之发生改变。当电子注的等离子体频率超过谐振腔的谐振频率时,谐振腔内的电磁场分布将发生很大的变化,出现了电子注内外电场方向相反和趋肤效应等现象。     

A partially reflecting metal cladding: its effect on the modes of dielectric optical waveguides

If the metal cladding of a dielectric optical waveguide is sufficiently thin to be only partially reflecting, then the waveguide modes differ from those of the conventional metal-clad waveguide. The TE modes are little affected by a variation in the metal thickness but the TM modes change considerably due to a coupling between the waveguide modes and the surface plasma waves supported by both the metal: dielectric interfaces and the metal film. It is the refractive index of the dielectric cladding which is remote from the guiding core that determines whether the lowest order TM mode is the TM₀ or TM₁ mode. This dielectric cladding also strongly influences the attenuation of the TM modes and, if the guide supports a TM₀ mode, then the attenuation of the TM modes far from cut-off are an order of magnitude higher than that of the corresponding modes when the guide cannot support a TM₀ mode. If the guide can support a TM₀ mode then its dimensions can be chosen such that it will support the TE_N and TM_N modes with equal phase velocities. A lossless approximation is used to develop an expression which will specify the required guide dimensions directly and parametric plots of these dimensions are discussed.     

Dual-core leaky optical waveguide as an integrated-optic polarizer

We present a design of a dual-core leaky waveguide that can be used as an integrated-optic polarizer. The proposed polarizer works on the principle of mode filtering. The structure is characterized by two cores, namely core-1 and core-2 and a high index layer in the upper-most region, such a structure supports leaky modes. The leakage losses of the modes have been calculated by using the transfer matrix method (TMM). Single polarization operation is ensured by high differential leakage loss between fundamental TE and TM modes. We show TE-pass operation with 0.5 dB/mm loss in TE₀ mode and 13 dB/mm loss in TM₀ mode, and TM-pass operation with 0.36 dB/mm loss in TM₀ mode and 7.45 dB/mm loss in TE₀ mode. Besides single-polarization operation, single-mode operation of the structure is ensured by high leakage loss of all the other higher-order modes.     

X波段过模弯曲圆波导TM01-HE11模式变换器研究

在波束波导和反射面天线的馈源应用中, 为了产生低副瓣且方向图等化的高斯波束, 需要将高功率微波转换为准高斯模HE₁₁模辐射. 本文利用弯曲圆波导可同时从TM₀₁模产生TE₁₁模和TM₁₁模的原理, 提出了采用双弯曲过模圆波导结构直接将TM₀₁转换为HE₁₁的模式变换器, 避免了常规微波领域中首先将TM₀₁转换为TE₁₁再用波纹式或半径渐变式TE₁₁-HE₁₁转换器转换为准高斯波束功率容量不足或尺寸过长的不足. 基于模式耦合理论和Taguchi优化算法对模式变换器的弯曲半径、相移直端长度及引入位置进行了优化, 使输出的TE₁₁和TM₁₁成一定比率, 以组成HE₁₁模式, 并对设计的模式变换器进行了全电磁波仿真分析, 结果表明输出波束的标量高斯含量在9.05–9.8 GHz范围内均高于99%, 理论功率容量可达4.5 GW. 关键词： 高功率微波 模式耦合理论 Taguchi优化算法 模式变换器     

Effects of a lossy thin plasma-film on metal-diffused LiNbO3 optical waveguides

I intend to investigate the effects of different kinds of partially reflecting metal film (plasma layer) on the wave characteristics of a stratified titanium-diffused LiNbO₃ optical waveguide. The mode number, the equivalent indices, the extinction coefficients, the field distributions and the powers carried in each layer are given as a function of the free-space wavelength, of the diffusion parameters, and of the opticc-axis orientation. Of course, the power of TM-like hybrid waves flows in opposite directions in the plasma and the other regions.For ac-axis varying in the transverse plane, the ith-order hybrid mode is rather complicated in the guide with an aluminum layer. There, in fact, the field mapping can be seen as an overlap of a TE _i with a TM _i+1, mode because of a sudden transformation of the TM₀ mode into a superficial plasma wave (SPW). On the contrary, with a silver layer, the hybrid field is a simple combination of a TE _i with a TM _i mode with no SPW growing.The guide losses assume the lowest values (1 dB/cm) for an Ag layer which is the prime candidate for making electro-optical or acoustic-optical devices. On the other hand, the nickel film causes the highest losses (66 dB/cm).     

On‐chip silicon 8‐channel hybrid (de)multiplexer enabling simultaneous mode‐ and polarization‐division‐multiplexing

An 8‐channel hybrid (de)multiplexer to simultaneously achieve mode‐ and polarization‐division‐(de)multiplexing is proposed and demonstrated experimentally on a silicon‐on‐insulator platform to improve the link capacity of an on‐chip optical interconnect. The present hybrid (de)multiplexer has four channels for each polarization. A polarization beam splitter based on a three‐waveguide coupler is used to combine/separate the fundamental modes of TE‐ and TM‐polarizations (TE₀ and TM₀). Six asymmetric directional couplers are cascaded for (de)multiplexing the high‐order modes (TE₁, TE₂, TE₃, TM₁, TM₂, and TM₃). The experimental results show all eight channels have low loss and low crosstalk (<−10 dB) over a ∼ 30 nm wavelength range.     

Numerical modelling of 8mm TM01-TE11 mode converter

A numerical study of TM₀₁-TE₁₁ circular waveguide mode converter, with its optimized size and structure, is presented in this paper. Many factors such as spurious modes, backward wave, perturbation functions of waveguide axis or radius, phase-rematching techniques and ohmic losses are taken into account for the influence to mode converter's efficiency and bandwidth. And the dimensions of an optimized model (f₀=35GHz. with input and output radius a₀=13.6mm) are given.     

高功率微波在等离子体填充波导中的谐波产生

采用等离子体流体理论，研究了高功率微波在等离子体填充波导中的谐波产生，导出了非线性波动方程. 对二次谐波产生进行了数值计算与分析. 理论分析和数值计算表明，高功率微波将在等离子体填充波导中激发起谐波，TE_0n模式与TM_0n模式的基波都将激发起TM类型的谐波. 关键词： 高功率微波 谐波产生 等离子体填充波导     

基于二维结构薄膜的偏振选择相位光栅的研究

利用二维结构薄膜构建了具有偏振选择特性的新型相位光栅,借助严格耦合波分析(RCWA)方法计算了光栅各级衍射强度随入射光波长及入射角的变化,发现在垂直入射情况下,波长600—640 nm范围内,相位光栅对横向电学(TE)模主要产生0级衍射,而对横向磁学(TM)模产生±1级衍射,在波长633nm处,0级衍射光的偏振消光比为109.8,±1级衍射光的偏振消光比为334.6.利用时域有限差分方法对这种相位光栅的偏振分束现象进行了模拟,偏振分离角在玻璃基板内可以达到10°左右,最后模拟了入射角为23°时光栅对不同偏     

X波段高功率微波选模定向耦合器

高功率、长脉冲是高功率微波技术发展的趋势,提高微波器件的功率容量成为一项重要的任务,使用过模器件可以有效提高微波源的功率容量,然而却会带来微波源中同时存在多种模式的问题。为了识别一个X波段长脉冲过模高功率微波源的输出主模TM01模式,设计了一种在线选模定向耦合器,进行了理论分析和模拟优化设计。当频率范围为9.2~9.6 GHz时,模拟结果显示该选模耦合器对TM01模的耦合度为-54 dB,在400 MHz带宽内定向性大于35 dB,对TM02模的抑制度大于15 dB,功率容量可达到3 GW以上。     

等离子体填充盘荷波导高频特性分析

从麦克斯韦方程和流体理论出发，推导了填充磁化等离子体慢波结构的基本方程.在大磁场情况下，对等离子体填充盘荷波导的色散特性和耦合阻抗作了研究，结果表明填充等离子体使色散曲线上移，耦合阻抗提高.等离子体填充产生出模式谱非常丰富的周期性低频等离子体模式(TG模式).当等离子体密度增加到一定程度后，场模TM₀₁模的频率范围和TG₀₁模的频率范围相近，两个模式互相耦合产生出新的混合模G₁,G₂.如果相对论行波管工作在混合模上，将会产生新的工作机理. 关键词： 盘荷波导 等离子体填充 色散特性 相对论行波管     

Dispersion characteristics of a slow wave structure with a modified photonic band gap

This paper studies the dispersion characteristics of a modified photonic band-gap slow-wave structure with an open boundary by simulation and experiment.A mode launcher with a wheel radiator and a coupling probe is presented to excite a pure TM 01-like mode.The cold test and simulation results show that the TM 01-like mode is effectively excited and no parasitic modes appear.The dispersion characteristics obtained from the cold test are in good agreement with the calculated results.     

双微波源共轴辐射馈线结构的设计

设计了一种将两个不同波段微波源输出微波馈向同一个馈源喇叭的双波段馈线结构。该结构不仅对两个微波源输出的TM01模进行了有效的模式转换,而且实现了两个波段的微波共用辐射天线。采用双弯曲圆波导模式转换器实现高频段微波源输出微波的模式转换和轴线的定量平移;采用中间模式为矩形波导TE10模的圆波导TM01模-同轴波导TE11模的模式转换器,实现低频段微波源输出微波的模式转换及与高频段微波源输出微波的共轴输出。数值仿真结果验证了设计思路的正确性。     

Method for synthesis of wideband multimode waveguide elements

We propose a modification of the iterative method for synthesis of waveguide mode converters, which allows obtaining various elements of microwave transmission lines with a wide operating frequency band. The efficiency of the synthesis is illustrated by the calculated waveguide components. This method makes it possible to synthesize converters with significantly improved characteristics, e.g., a converter of the TM_0,1 mode to the rotating TE_3,1 mode, a converter of the TM_0,1 to the TE_1,1 mode, a converter of the TE_1,1 mode of a smooth waveguide to the HE_1,1 mode of a corrugated waveguide, and a waveguide 90° bend for the TE_1,1 mode. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 9, pp. 793–799, September 2007.     

Generation of radially polarized mode using an active cylindrically symmetric birefringence fiber

A class of active fiber is presented as gain mediums of fiber lasers, where a silica layer with spoke-like air slits is introduced between the active core and cladding to obtain birefringence. With an appropriate choice of the design parameters, the fiber can support only the HE₁₁ and TM₀₁ modes. Furthermore, the numerical results show that, corresponding to the optimal rare earth doping profile, the fiber lasers can output a pure TM₀₁ mode with about 79% slope efficiency without using other mode-selective elements.     

具有变态光子带隙结构的相对论Cherenkov辐射源的研究

提出了一种变态光子带隙结构,研究了由这种结构构成的周期慢波系统的Cherenkov辐射源的特性. 利用高频仿真软件以及三维粒子模拟软件对变态及常态光子带隙慢波系统中类TM₀₁模的色散特性及注-波互作用物理过程进行了模拟研究. 结果表明,在变态光子带隙慢波系统中,类TM₀₁模纵向场分量沿角向分布均匀性得到明显改善,能有效抑制非对称模式,提高输出频谱纯度及注-波互作用效率. 关键词： Cherenkov辐射源 变态光子带隙结构 慢波系统 三维粒子模拟     

Submillimeter wave-guiding on thin dielectric films

The excitation and propagation of guided submillimeter waves (λ = 0.337 mm) is demonstrated on stretched, self-supporting sheets of polyethylene (PET) and polyterephthalate (PTER). Prism-film couplers serve for input and output. The PTER films show negative birefringence (n₀ = 1.76, n_e = 1.68). An attenuation of 0.25 dB/cm was measured for the TM₀ mode on a 12 μm thick PTER film.     

Study of Disk-Loaded Waveguide Filled with Plasma

Recently disk-loaded waveguide has been widely used in high-power traveling wave tubes (HPTWT). It has been shown in many experiments that the interaction efficiency and output power can be increased greatly by injecting plasma into the vacuum microwave device. Using field analysis, the dispersion characteristics and the interaction impedance of the disk-loaded waveguide filled with plasma are analyzed in a strong longitudinal magnetic field. In conclusion, the frequency of the TM₀₁ mode increases as the density of the plasma increases. It also can be found when the plasma density increases to a large scale, the TM₀₁ mode of the disk-loaded waveguide overlaps the TG mode, these two modes couple each other and form the new hybrid modes.     

矩形波导与圆柱波导或圆柱谐振腔间的小孔耦合

本文讨论了三种不同系统的小孔耦合的近似解法:矩形波导与圆柱波导的同轴耦合,矩形波导中的TE₁₀型波与圆柱谐振腔中的TM₁₂₀型波间的耦合和矩形波导中的TE₁₀型波与圆柱波导中的TM_mn型波间的耦合。通过这几个问题的解法,我们希望读者可以看到处理复杂微波元件问题时所需的从物理概念出发的灵活应用已有方法的必要性。这里提供的几个公式有着广泛的应用范围而是在现有文献中探讨得不够的。这里介绍的方法可以应用到其他新的微波网络问题中去。     

Investigation of pertubation effect for plasma in TM010-mode microwave excited gas laser

Characteristic equation for the cylindrical TM₀₁₀-microwave plasma cavity is given. Analytical expression and perturbation formula for the resonant frequency of TM₀₁₀ mode dependence of plasma are derived. A comparison between exact and approximate solution shows that the perturbation theory can be used accurately to analyze the detuning of the cavity caused by microwave plasma with a tolerance less than 5%.