金属包层对称平面单轴晶体波导的模式场(Ⅱ)

对于晶体光轴平行于波导界面的结构,讨论了光在金属包层对称平面单轴晶体波导(波导层是单轴晶体,两个波导界面均为金属)内的传输特性.解析地得到了这种结构下波导模式场的精确解.模式场的性质因单轴晶体的性质不同而异.对于正单轴晶体,波导的主模是横电波,任何频率的光波均可激励该模式;当频率满足一定条件时,波导内传输单模,否则,将激励起高阶模式.高阶模既非TE波,也非TM波,而是两者耦合而成的混合模.对于负单轴晶体,波导的主模是一种混合模,该模式同样可被任何频率的光波所激励;当频率满足一定条件时,波导内传输单模,否则 关键词： 平面金属波导 单轴晶体 模式场 混合模     

Mode theory of three-layer cylindrical waveguides and its application to aurum(Au)/polystyrene(PS)-coated terahertz hollow waveguides

In this paper, we present a generic mode theory for the three-layer cylindrical waveguides consisting of three arbitrary material mediums. Based on derived eigenvalue equations of the TE, TM, and hybrid modes, the mode conditions of metal/dielectric-coated terahertz hollow waveguides are extracted. In addition, we quantitatively describe both the effective refractive indexes and the loss characteristics of the aurum/polystyrene-coated terahertz hollow waveguides operating at the TE₀₁, TM₀₁, and HE₁₁ modes. It is indicated that the loss coefficient of the TE₀₁ mode can be much lower than that of the TM₀₁, and HE₁₁ modes, and, especially, can tend to that of the terahertz wave in air. So the TE₀₁ mode is very significant for the hollow waveguides in term of low loss propagating of the terahertz wave. We expect these results to enable a variety of new long-distance THz applications in sensing, detecting and communicating.     

带状束高功率微波源宽通带收集极

设计了一种适用于带状电子束高功率微波源的宽通带收集极,在有效吸收束-波相互作用后的带状电子束的同时,保证了带状电子束高功率微波源的工作模式矩形波导TM11模式高效率地通过。研究结果表明：在13~27 GHz范围内,功率传输效率大于95%,这一宽通带特性使得该类型的收集极与带状电子束高功率微波源能够更好配合,显著提高了微波源的模拟优化和实验调试效率;TM11模式微波的传输效率对收集极厚度和长度等参数不敏感;该类型收集极结构具有良好的散热能力,在不加外部水冷装置的条件下,仅靠空气自然对流冷却和辐射冷却,可以承受电流3 kA、电压300 kV、脉冲宽度30 ns及重复频率50 Hz带状电子束的连续冲击。     

Ka波段8路径向波导空间功率分配（合成）器

通过理论研究以及高频仿真相结合的方法分析设计了一款新型Ka波段8路径向波导空间功率分配（合成）器。研发的新结构输入输出段为标准矩形波导结构,代替了传统功率分配（合成）器输入输出段的同轴结构,这种新型全金属结构更加简单紧凑,更易于加工。仿真结果表明：功率分配（合成）器工作带宽达到了34%（12 GHz）,基本覆盖整个Ka波段;全频带内反射系数S11低于-20 dB,各支路的相位差均小于5。通过在同轴波导渐变段引入切比雪夫渐变结构,在减小了器件尺寸的同时,在整个频带内的网络S参数也不错。这款新型Ka波段8路径向波导功率分配（合成）器将应用于前级固态功率放大器,推动回旋行波管项目研发。     

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.     

一种带有U形波导的交叉信道单微环电光开关

本文利用耦合模理论,电光调制理论和传输矩阵法,提出了一个带有U形波导的交叉信道单微环电光开关的器件模型,并在谐振波长为1561 nm的情况下对该器件进行了仿真计算.结果表明,该电光开关的开关电压约为400 V,串扰小于-30 dB,插入损耗小于4 dB,开关时间仅为5.4 ps,其中微环上的上升和下降时间仅为0.32 ps.此外,该电光开关由单刀双掷开关控制,通过在微环和U形波导上加载驱动电压可实现三种开关状态,不仅可以实现光信号在两条输出信道的选择,还可以使两条信道同时有光信号输出.     

正弦波导高频特性分析

对一种全金属慢波系统—–正弦波导的高频特性进行了理论分析.在用一系列相连矩形阶梯逼近余弦槽的基础上,对慢波结构进行了合理的区域划分,获得了各区域的场表达式.考虑槽区的高次驻波项,采用场匹配和导纳匹配相结合的方法,导出色散方程和耦合阻抗表达式.以应用于220 GHz行波管的正弦波导为例进行高频特性的数值求解,理论计算值与全三维电磁软件CST-MWS的仿真值符合良好.在此基础上,详细分析了尺寸参数变化对正弦波导高频特性的影响.     

MIM结构的SPP模式理论与仿真计算研究

为了进一步明确MIM （Metal-insulator-metal）波导结构的SPP （Surface plasmon polariton）模式特性,建立了MIM结构的SPP模式关系、激发系数和反射系数的理论模型。仿真数值计算结果表明：较大的介质厚度的TM基态模式衰减超过了振荡模式衰减,与传统的介质波导明显不同;TE模式表现为失真的介质光波导模式特性,其传播距离要远大于TM₀;MIM结构中腔的Q值随着长度增加而增大,表明了SPP反射受限;腔的品质因数改变与端面关系密切;MIM波导可以在具有更大Q值下确保光波更好地耦合成需要的SPP模式。     

Optimizing Design for the Traveling Wave Electrodes in Low-Drive High-Speed Electro-Optic Polymer Modulators

Electro-optic (EO) polymer modulators are very promising in the realization of cost-effective and high-performance optical transmissions. In this article, general strategies and specific designs of the traveling wave electrodes in EO polymer modulators were presented to reduce the modulator drive power while maintaining a broadband response. The optimum device parameters and corresponding conditions were estimated using finite element method based on electrode design. In calculating the results, the comprehensive characteristics of polymer modulator with 1.21 V half-wave voltage and 91 GHz bandwidth was demonstrated with electro-optic interaction length is 20 mm, electro-optic coefficient is 55 pm/V, and operation wavelength is 1.319 μm. These results agree with the 0.8 V half-wave voltage and 30 mm electro-optic interaction length reported in Science. In the five designs presented, a hybrid electrode structure combining CPW and microstrip lines were advanced. The characteristics of this structure are like that of microstrip lines with a single-arm electrode on one arm of the waveguide, but it solves the problem of microstrip to coaxial line transition and corona polarization.     

Progress in Optical Waveguiding Thin Films

Overview of recent activities in the development of active and passive thin film waveguides, waveguide lasers and laser-deposited waveguiding films is given. Published results and parameters are summarized. The focus is on films fabricated by laser deposition.