New millimetre-wave isolator containing a semiconductor rod in a circular waveguide

Attenuation characteristics of an InSb waveguide isolator at 94 GHz and 75 K are given experimentally and theoretically. The structure is a rod of InSb placed coaxially in a circular waveguide. Over 20 dB isolation is measured, with 3 dB forward loss.     

Hollow-Cylinder Waveguide Isolators for Use at Millimeter Wavelengths

The device considered in this study is a semiconductor waveguide isolator consisting of a hollow column of a semiconductor mounted coaxially in a circular waveguide in a longitudinal dc magnetic field. An elementary and physical analysis based on the excitation of plane waves in the guide and a more rigorous mode-matching analysis (MMA) are presented. These theoretical predictions are compared with experimental results for an InSb isolator at 94 GHz and 7.5 K.     

Theoretical Analysis of the Operation of the Field-Displacement Ferrite Isolator

A theoretical analysis of the resistance-sheet isolator is carried out, and numerical solutions are obtained for the forward and reverse propagation constants of the distorted dominant mode in a rectangular waveguide containing a transversely magnetized thick ferrite slab displaced slightly from the side wall. The microwave electric field patterns within the waveguide are plotted for several values of the physical design parameters of the isolator for which experimental performance data have been reported. Field patterns are used to describe the principles of the isolator and to select the optimum values of slab thickness, internal dc magnetic field, ferrite magnetization, and location of the slab in the waveguide for the idealized isolator. Evidence is presented to show that it is necessary to use a comparatively thick ferrite slab located in a very small usable range of distances from the side wall. The appropriate value of internal dc magnetic field is simply related to the magnetization of the ferrite and to the frequency. It has not been necessary to take into account the perturbing effects of the resistance card or matching techniques in order to explain the basic design principles.     

Propagation Properties of a Modified Slot Surface Plasmonic Waveguide

In this paper, we present a modified slot surface plasmonic waveguide formed by metallic rod, core dielectric layer, and metallic film on the substrate. Using the finite-difference frequency-domain method, modal field distribution are analyzed firstly. Results show that the fundamental mode could be well confined in the space between the metal rod and the metal film. The dependence of modal field distribution, effective index, and propagation length of the fundamental plasmonic mode without gain on dielectric constant of the core layer, geometrical parameters, and working wavelengths are analyzed and discussed. A kind of available gain dielectric medium was used for the core dielectric layer to extend the propagation length. Results show that the propagation length can be extended observably with the help of the gain dielectric medium. Finally, effect of the thickness of the core dielectric layer on modal field distribution, effective index, and propagation length are analyzed and discussed. Since the modal field distribution, effective index, and propagation length can be controlled by adjusting the geometrical parameters, dielectric constant and gain of the core layer and working wavelengths of the waveguide, this kind of surface plasmonic waveguide can be applied to the field of photonic device integration and sensors.      

Room temperature solid-state plasma nonreciprocal microwave devices

Nonreciprocal microwave propagation at room temperature in a waveguide which contains of a thin slab n-InSb has been demonstrated by the construction of an isolator, a three-port circulator, and a variable power divider, all operating at K-band frequencies. A forward loss and an isolation of 3 and 15 dB, respectively, was observed for the isolator; the forward and backward losses between adjacent ports of the circulator were 3 and 20 dB, respectively, and the power ratio of the divider could be varied from 1 to 10 for a given direction of the magnetic field. Transmission losses of about 3 dB were present in the forward direction and in each case, all but 1 dB of these were shown to be due to reflections resulting from impedance mismatch.     

Numerical calculation of the radiation from a guiding structure of arbitrary cross-section

A quadrature scheme is described for the calculation of the radiation field of an open-ended guiding structure directly from the longitudinal field components of the mode in the aperture. The calculated radiation pattern for a rectangular waveguide and a regular polygon dielectric rod agree well with known results. Radiation patterns for rectangular dielectric rod are also presented.     

The Groove Guide, a Low-Loss Waveguide for Millimeter Waves

A new waveguide for the low-loss transmission of millimeter waves is presented. The guide consists of two parallel conducting walls with grooves in the central region of the guide cross section. The grooves run along the guide in the direction of the wave propagation. It is shown that the waveguide, if excited in the TE-wave mode, has properties similar to those of the H guide, which contains a dielectric slab between the conducting walls in the center. The new guide is characterized by an exponential transverse decrease of the field distributions in direction from the center and by low attenuation. Theoretical considerations dealing with the field distribution and the data of the guide are presented.     

Analysis of the coupling of two non-parallel dielectric rod waveguides

In this paper the coupling between two closely spaced single mode dielectric rod waveguides is investigated when the corresponding propagation axes are not in the same plane. An approximate analysis is presented by assuming only first order interaction between the guided waves. For a given incident HE₁₁ mode (in one of the rod waveguides) the coupled wave amplitudes are computed in the other waveguide for both propagation directions. Numerical results are presented for several coupling geometries.     

任意截面波导的模式截面场的数值分析

给出了任意截面波导的传输特性的时域差分（FDTD）数值方法的一般分析方法,首次提出了用数值方法建立任意截面波导中各模式横向场分量截面场分布的方法,为证明这种方法的有效性,计算了常用空气填充的Ka波段矩形波导中主模（H10模）和一次高阶模式H20模的截止波长和Ey场分量,其与理论值的安全一致性表明所提出的方法是正确的。作为应用例子给出了一种新型的五边形波导的最低四个模式的传播常数及主模式和第一高次模的电场在波导横截面的场分布图。     

Detailed comparison of two approximate methods for the solution of the scalar wave equation for a rectangular optical waveguide

Two approximate methods for the determination of the fundamental mode of an optical waveguide with rectangular core cross section and step refractive-index profiles are presented and analyzed thoroughly. Both methods are based on Galerkin's method. The first method uses Hermite-Gauss basis functions and the second uses the guided and nonguided slab waveguide solutions as basis functions. The results are compared with results from an accurate circular harmonic analysis. Both methods provide values of the normalized propagation constant with errors less than 0.1% for practical rectangular single-mode waveguides. The slab waveguide method is the fastest, and even when only one slab waveguide mode is used the propagation constant for the fundamental mode can be calculated with an error of less than 1%. The slab waveguide method also gives very accurate results for the propagation constant for higher order modes.<>     

Propagation characteristics of dielectric-rod-loaded waveguides

A general technique for calculating the propagation characteristics of a waveguide with arbitrary cross-sectional shape loaded with a circular dielectric rod is presented. The waveguide fields, which are represented as a sum of functions satisfying the homogeneous Helmholtz equation and the boundary conditions at the rod surface, are point-matched at the surface of the waveguide. Numerical examples of a rod centered in a square guide and off center in a circular guide are given, and results for a rod centered in a rectangular cavity are compared with measured data     

Dielectric Loaded Elliptical Waveguides

Wave propagation in a metallic elliptic waveguide loaded with a dielectric rod or a dielectric lining is investigated theoretically. The mode spectrum for both slow and fast hybrid modes is obtained by numerical solution of the characteristic equations. Correspondence is established between the modes of the loaded and unloaded elliptical waveguides. Typical field plots for /sub e/HE/sub 01/ and /sub 0/EH/sub 01/ modes are presented. Power flow, power loss, and attenuation are obtained using a perturbation method.     

InP基稀释光波导特性分析

从InP基稀释光波导的基本模型出发,利用有限差分波束传播（FD-BPM）算法,推导了InP基稀释光波导的有效折射率,对其进行了数值计算;根据光传输损耗方程,分析了稀释波导传输损耗产生的原因;对稀释光波导中TE/TM模式传输进行了详细的数值分析和模拟计算,并分析了其模场分布曲线。     

Design of a Full Waveguide Bandwidth High-Power Isolator

An analysis of the microwave fields in rectangular waveguide indicates that circular polarization of the H-vector components exists at two planes only and the location of these planes is frequency dependent. Also, an examination of Kittel's theory reveals that resonance in ferrites can be made to occur at different frequencies for a constant value of dc magnetic biasing field provided the ferrites are characterized by different values of saturation magnetization. These two effects have been used concurrently in the design of an X-band waveguide isolator for operation over a 45 per cent bandwidth, and at high power levels. The theory underlying the design of this isolator is presented. Included is a treatment of the parameters which affect the isolator design. Finally, an operative isolator is described and its experimental characteristics are reported.     

介质加载型混合表面等离子体波导的损耗特性

为实现长距离传输及亚波长尺度的模式限制,在传统介质加载型表面等离子结构的基础上,设计了一种微孔介质加载混合表面等离子体波导,采用时域有限差分法(FDTD)对该波导模式场分布及传输特性进行了相应的研究。研究表明所设计的波导结构具有较强的局域场限制,通过在孔内填充增益介质,使混合等离子体波导的传输损耗得到了补偿,输出端的表面等离子激元实现了增益放大。结果表明,通过调整波导的几何参数和电磁参数,可以显著提高波导的场限制,降低波导本身的损耗,其中当孔与金属之间距离为44 nm时,波导的损耗达最小约为-13 dB/m。这一设计可以为光子器件集成提供一定的理论和实验借鉴价值。     

新型声表面波湿度传感器的研究

乐甫(Love)波其质点振动方向垂直于传播方向,同时又平行于基片表面,在基片法线方向上无振动分量。因此当基于Love波的电子器件在接触液体时Love波能量损耗很少,因而乐甫波声表面波(SAW)传感器主要用于液相检测。在石英上表面及在其上面淀积的SiO2薄膜中激发、传播的乐甫波对SiO2薄膜质量的变化很敏感,因此该文研究了基于乐甫波的湿度传感器感知气体环境的湿度含量。该文乐甫波湿度传感器采用42.75°Y-旋转切割石英基片,传播方向为[0°,132.75°,90°]。吸湿膜采用APCVD制作的多孔SiO2薄膜,此类膜比PECVD制作的SiO2膜疏松,吸湿、脱湿迅速。传感器灵敏度为62kHz/%RH,最大湿滞约3%,测得的湿敏特性、迟滞特性表明,Love波SAW湿度传感器线性度较好,实验验证了该结构具有很好的气体测试前景。     

3kW射频板条CO2激光器抛物面非稳波导腔研究

为了提高传统球面镜腔3kW射频板条CO2激光器光束质量,设计了新型抛物面镜负支非稳-波导混合腔;结合标量光束的瑞利-索末菲衍射理论与特征向量法,研究了大菲涅耳数下镜面类型对非稳波导混合腔光场传输特性的影响;利用矩形波导理论、1维近似分析得出了波导传输损耗及偏振情况。结果表明,将非稳方向输出镜和尾镜改为与光轴交点处曲率半径为R1=951.32mm和R2=1088.68mm的抛物镜面,能够避免尾镜漏光,可有效改善模式鉴别特性;常用波导电极镀膜材料中,镀铝电极内波导方向传输损耗最小,传输光场为x偏振的EH1模。采用电极镀铝的抛物面非稳波导腔能够降低损耗、提升光束质量。     

Simulation of polarization converter formed by poling-inducedpolymer waveguides

A polarization converter using electrooptic (EO) polymer waveguides is proposed and it is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium. First, an efficient structure of poling electrodes is proposed for the fabrication of TE-mode poling-induced waveguides in EO polymer. For given electrode structures of both TE-mode and TM-mode waveguides, poling-induced dielectric tensors are calculated by the finite-element method to provide refractive index distribution, data for VBPM simulation. It is shown numerically that the poled TE and TM mode waveguides work efficiently as the corresponding polarization filters. Then, new poling electrodes are suggested to fabricate a waveguide device formed by connecting the TE and TM mode waveguides adiabatically with a slowly varying structure. This waveguide device has the optic axis slowly rotating as one moves along the propagation direction, so that it will act as polarization converter. VBPM simulation shows that the polarization of the guided mode rotates following the optic axis distribution. Polarization conversion is demonstrated successfully with high conversion efficiency and low excess loss     

Analysis of a Post Discontinuity in an Oversized Circular Waveguide

This paper presents the analysis of scattering characteristics of a radially directed thin post in a circular waveguide using the method of moments. Electric type dyadic Green's function has been used to compute the scattered field in a circular waveguide considering variation of current only in the axial direction of the post. Simulated data on return loss and power coupling in the dominant mode and higher order modes have been compared with the data computed using Ansoft's High Frequency Structure Simulator. The data on return loss and coupling for the incident ${rm TE}_{11}$ mode have been compared with experimental data.      

Control of the spectrum of the near-field Bloch waves in a waveguide periodically loaded with thin InSb layers

The realizability of a new propagation mode of electromagnetic waves and the possibility of controlling the spectrum of these waves in a rectangular waveguide periodically loaded with thin InSb layers are studied theoretically. It is shown that the fundamental passband of this periodic structure, which is similar to a photonic crystal, is substantially lower than both the cutoff frequency of the waveguide itself and the frequency corresponding to the plasma resonance in the material of the semiconductor loads. It is found that the lower passband is characterized by a negative dispersion corresponding to propagation of backward waves.