斜向场双层波导中导波光模式转换和衍射效率

本文研究了斜向场下双层磁光薄膜波导中导波光与静磁正向体波之间的相互作用。在静磁波频率为1．9－3．4GHz的范围内,计算了不同磁场倾角下导波光的衍射效率和模式转换效率。结果表明,在相匹配条件下,通过改变磁场倾角、微带线的宽度和孔径,可以使导光的衍射效率得到较大的提高。斜向场下使用YIG材料制成的双层波导与单层波导相比,在增进导波光的衍射效率具有较大的优势和潜力。     

可调谐非色散延迟线

使用表面磁导率法得到斜向磁化金属/电介质/钇铁石榴石(YIG)/钆镓石榴石(GGG)/金属多层电介质结构中静磁波的传播方程.通过分析静磁正向体波(MSFVW)和静磁反向体波(MSBVW)延迟特性设计出级联MSFVW-MSBVW延迟线系统,该系统通过调节MSBVW延迟线激发场角起到控制非色散延迟时间的作用.数值计算得到一个近500MHz的非色散延迟带宽,延迟时间具有156.4～186.6ns/cm的可调范围.     

用于光通信的新型磁光Bragg器件的优化分析

采用变分法研究了横向不均匀偏置磁场作用下掺Bi的YIG薄膜中微波静磁波对导波光的Bragg衍射效率,理论计算得到的衍射效率曲线与实验结果基本一致.计算表明,采用适当的不均匀偏置磁场、在一定范围内增大激发电流以及优化波导结构等方法可有效提高磁光Bragg器件的衍射性能;减小Bi:YIG薄膜厚度也可提高导波光衍射效率,但磁光带宽有所减小.     

基于YIG单晶薄膜的陷波器设计

针对基于环球耦合谐振的钇铁石榴石(YIG)小球陷波器装配调试工艺复杂、不利于多通道集成的问题,提出了一种采用静磁波技术来实现YIG单晶薄膜陷波器结构与设计方法.该文通过对单晶薄膜陷波器工作原理的分析,静磁反向体波的角频率与波数(ω-k)色散特性与微带激励谐振换能器的静磁波激励特性的数值计算及器件仿真优化,设计了调谐工作...     

垂直不均匀磁场中静磁波的传播特性

本文理论分析了垂直不均匀磁场作用下磁性薄膜中静磁波的传播特性,具体计算了抛物线分布的不均匀磁场对静磁对表镣波振幅的影响,计算表明,在适当分布的不均匀场作用下,与均匀磁场情形相比,波导中传播的 振幅有所增加,从而也增强了静民导波光相互作用时的射效应。     

多层窄样品中静磁表面波宽度模的色散特性研究

本文建立了具有任意参数多层薄膜结构的窄样品中静磁表面波宽度模的普遍色散关系,适用于利用多层薄膜控制静磁表面波色散特性的所有情况.对两周期 多层膜结构窄样品中静磁表面波宽度模的色散特性进行了数值计算,得到了多层膜中的高阶宽度模式,多层薄膜结构的参数可以有效地控制静磁表面波的色散特性,样品宽度效应对色散也有明显的影响.根据数值计算结果对不同宽度的YIG薄膜样品在4.2~5.2GHz的频率范围进行实验,实验测试结果与理论分析相吻合.     

微波静磁波模式特性分析

全面分析了磁光薄膜波导中磁化方向对微波静磁波传播模式的影响。给出了不同模式的静磁波色散方程和带宽的一般表达式,首次完整地展现了静磁波的模式分布图。所得结论可用于分析倾斜磁场在改善基于静磁波的新型磁光B ragg器件衍射性能方面所起的作用。     

静磁正向体波与导波光的非共线相互作用

在考虑静磁正向体波（MSFVW）传播损耗及微带换能器耦合损耗的情况下，利用耦合模理论推导出导波光（GOW）衍射效率的表达式，并针对掺铋钆铁石榴石（Bi-YIG)薄膜波导和钇铁石榴石（YIG）波导计算了GOW衍射效率的频率响应曲线。数值计算表明，虽然MSFVW在Bi-YIG薄膜中的传播损耗大于YIG薄膜，但前者具有很大的一级磁光系数，故Bi-YIG波导中GOW的衍射效率仍远大于YIG波导。     

静磁前向体波(MSFVW)信道接收器的研究

静磁前向体波(MSFVW)要求外加直流偏置磁场和静磁波波导YIG膜平面相垂,因而极易安排直流磁路和微波电路。把一个MSFVW阵列置于一个线性渐变外磁场中,每个滤波器中心频率不同,形成一个信道接收器,可完成不同频率信号的实时分离。本文从理论和实验说明这种器件的特性,并指出器件实用化尚需进行的工作。     

磁光薄膜波导中光导波的模式转换和衍射效率计算

根据耦合模理论,应用微扰方法分析了Ｂｉ：ＹＩＧ薄膜波导中斜向静磁场对静磁波与导波光相互作用的影响,计算了斯托克斯和反斯托克斯相互作用中导波光的模式转换效率和衍效率。     

Propagation characteristics of magnetostatic waves

The present paper reviews the propagation characteristics of the three magnetostatic wave-types that can exist in a ferrimagnetic film such as the commonly used epitaxial yttrium-iron-garnet (YIG) film, viz., magnetostatic surface waves (MSSWs), magnetostatic forward volume waves (MSFVWs) and magnetostatic backward volume waves (MSBVWs). The pronounced inherent dispersiveness of these waves and methods of controlling or tailoring dispersion are discussed. Other propagation characteristics such as diffraction and propagation loss and the envelope distortion of acw pulse in propagating through such a dispersive medium are briefly described.     

Finite-element analysis of magnetostatic wave propagation in a YIGfilm of finite dimensions

A unified numerical approach based on the finite-element method is described for the magnetostatic wave propagation in a YIG film of finite dimensions. Both magnetostatic surface wave modes are treated. The validity of the method is confirmed by calculating the magnetostatic wave modes in a YIG-loaded rectangular waveguide and in a YIG film of finite width. The numerical results of a YIG films with nonuniform bias field along the film width are also presented, and the effects of bias field distributions on the delay characteristics and potential profiles are examined     

Magnetostatic Wave Propagation in a Finite YIG-Loaded Rectangular Waveguide

The propagation of magnetostatic waves (MSW) in a waveguide partially loaded with a low-loss ferrite slab is investigated theoretically. The most common low-loss ferrite material used for MSW propagation is epitaxial yttrium iron garnet (YIG). A YIG slab is placed inside and along the guide and not in contact with the sidewalls of the wavegnide. The dc magnetic field is assumed to be parallel to the YIG slab and perpendicular to the direction of propagation. Using the integral equation method, the dispersion relation is found to be an infinitely large determinant equal to zero. Proper truncation of this determinant and numerical analysis to find its roots are carried out in this work. It is seen that in order to obtain high values of group time delay, the YIG slab must be narrow and placed at the bottom of the guide. On the other hand, to maximize the device bandwidth, a narrow YIG slab positioned at the top inside surface of the waveguide is preferred. It is also noticed that there exists a tradeoff between the time delay and the device bandwidth and that maximization of one property leads to a poor value in the other. Thus, some design compromises should be made. It is also observed that the frequency range of operation of the device can be adjusted by an external magnetic bias field. This property of tuning the device to operate in any frequency range adds an extra dimension of flexibility to the operation and also to the design of these devices.     

Magnetostatic wave propagation in YIG double layers

Calculations are presented for the magnetostatic surface wave propagation characteristics in single-crystal yttrium-iron-garnet (YIG) double layers with arbitrary direction of magnetization. The induced uniaxial magnetic anisotropy field is assumed to be different in the two layers; hence, the magnetization in one layer is aligned at an angle with respect to the magnetization direction in the other layer. The magnetostatic field interactions between layers depend on the angle between the two magnetization directions and on the separation between the two YIG layers. The wave propagation directions and time delays in each layer can be strongly affected by the use of an applied magnetic field and the magnetostatic coupling between the two layers, as well as by the uniaxial anisotropy energy in each layer     

Boundary Element Method Approach Magnetostatic Wave Problems

In this paper, the technique for application of the boundary element method (BEM) to analysis of magnetostatic waves (MSW'S) is established. To show the availability of the technique, two types of waveguides for the MSW are studied one is a waveguide constituting a YIG slab shielded with metal plates and the other is a waveguide consisting of an unshielded YIG slab. With the former structure the results obtained by the present technique are compared with the analytical solutions, and with the latter the BEM is compared with Marcatili's approximate method since there is no analytical solution in this case. Those comparisons are performed successfully for both cases. The paper concludes that the BEM is useful and effective for analysis of a wide range of MSW problems.     

Magnetostatic wave convolvers

The present paper reviews recent theoretical results, and reports initial experimental results, on the convolution of contra-propagating magnetostatic forward volume waves (MSFVWs), in the form of cw signals or time-limited cw pulses, in an epitaxial yttrium iron garnet (YIG) film. Computations of the convolver bilinearity factorF _int indicate an efficient convolution process over a wide bandwidth, with values ofF _int that are of the same order as, or better than, the reported experimental results for MSW convolution in a YIG cylindrical or plate geometry. The values of F_int determined experimentally are in excellent agreement with theory. These results are of interest to microwave system developers particularly if bandwidths of 1 GHz or larger can be realized in practice. A limiting feature of magnetostatic wave (MSW) convolvers is that the maximum delay time of a delay line that is realizable without excessive insertion loss is in the order of 0.5s. The advantage of MSW convolvers, of course, lies in their ability to perform signal processing directly at microwave frequencies, and in applications such as electronic warfare the advantageously large bandwidths would mitigate the limitations in delay time.This work was supported in part by a contract from the AIL Division of the Eaton Corporation.     

Finite-Element Solution of Planar Inhomogeneous Waveguides for Magnetostatic Waves

A unified numerical approach based on the finite-element method is described for the solution of planar inhomogeneous waveguides for magnetostatic waves. Both magnetostatic volume wave and magnetostatic surface wave modes are treated. The validity of the method is confirmed by calculating the magnetostatic wave modes of layered YIG films. The numerical results of inhomogeneous YIG films with alpha-power magnetization profile are also presented, and the effects of magnetization inhomogeneities on the delay characteristics and potential profiles for magnetostatic forward volume wave, magnetostatic backward volume wave, and magnetostatic surface wave modes are examined.     

Magnetic Waves for Microwave Time Delay-Some Observations and Results

Some topics of exchange-coupled spin waves and magnetostatic waves in narrow line width ferrimagnetic materials for electronically variable time delay of microwave signals in the microsecond realm are discussed. The excitation problem is treated by use of transmission-line analogs. A method of excitation of spin waves by microscopic geometries is suggested, and an estimate of its efficiency given. Results of experiments of magnetic wave excitation in axially magnetized YIG rods are presented. Here very strong excitation of signals with high dispersion and microsecond time delay that is a sensitive function of H/sub dc/ were found. These signals possess most of the characteristics predicted for Fletcher-Kittel waves. Other signals, with less dispersion and a much more slowly variable time delay, were also found.     

Edge-Guided Magnetostatic Mode in a Ridged-Type Waveguide (Short Papers)

A ridged-type magnetostatic waveguide is analyzed using the boundary element method. A bias magnetic field is applied perpendicularly to the surface of an yttrium-iron-garnet (YIG) film grown on a gadlinium-gallium-garnet (GGG) substrate. The dispersion curves and the potential profiles obtained in this paper show that the mode has a strong nonreciprocal property and is a kind of edge-guided mode which propagates along either side of the ridge, depending upon the direction of the bias field and the direction of the wave propagation. In addition, the authors emphasize the fact that the boundary element method is useful for analysis of a complex structure in the field of magnetostatic wave (MSW) devices.