Transverse Discontinuities in Nonreciprocal Waveguides

The mode-matching technique is used to analyze transverse discontinuities in nonreciprocal waveguides. The difficult orthogonality relations are circumvented using a Galerkin approach. The elements of an exact three-element equivalent circuit for an infinitely thin metallic diaphragm are evaluated. Each element has two values, one for each direction of propagation. The numerical results show the same trends as those obtained experimentally in a similar configuration.     

法拉第磁光波导的耦合模分析

利用法拉第磁光效应可以设计光纤磁场传感器。在磁场传感过程中，磁光晶体薄膜波导的TE模和TM模式之间将发生转换，：其转换效率与磁光晶体的法拉第旋转角度和双折射有关。本文建立了磁光波导的耦合模方程，分析了磁光波导中的TE—TM模转换，提出了通过减小线性双折射和增大法拉第旋转角来提高TE—TM模耦合效率的措施，这些措施有利于增大光束TM模的输出功率并提高光纤磁场传感器的灵敏度。     

Nonreciprocal Polarization Converter Consisting of Asymmetric Waveguide With Magnetooptic Cladding: Theory and Simulation

A nonreciprocal polarization converter compatible with InP-based photonic integrated circuits is proposed. The device consists of an asymmetric InGaAsP waveguide combined with a ferrimagnetic cerium-substituted yttrium iron garnet layer. It makes use of the nonreciprocal conversion of the polarization state in the waveguide. A nonreciprocal TE–TM conversion efficiency of 93% at 1.55 $mu{hbox {m}}$ wavelength can be obtained with a device length of 0.27 mm.      

Nonreciprocal Wave Propagation in Semiconductor Loaded Waveguides in the Presence of a Transverse Magnetic Field

Approximate solutions for the complex propagation constant in semiconductor loaded waveguides are obtained by expansion of the fields in terms of a finite number of the empty waveguide modes. Solutions are obtained for the case of partial loading in the narrow dimension of the guide, which explicitly exhibit the non-reciprocal effects observed in the presence of a transverse magnetic field. Coupling between the TE/sub 10/ and TM/sub 11/ empty waveguide modes is shown to explain qualitatively the observed experimental effects. Good quantitative agreement with experiments using Si samples is obtained.     

A Nonreciprocal Circular Polarizer

A nonreciprocal circular polarizer has been developed. This ferrite device converts linear polarization propagating in rectangular waveguide into circular polarization propagating in circular waveguide. The sense, right- or left-hand, of the circular polarization is determined by the direction of a longitudinal magnetic field applied to the ferrite. If one sense of circular polarization, e.g., right-hand, is transmitted, then only left-hand circuIar polarization can be received. Performance data indicate good ellipticity with reasonable loss and VSWR for two models of the circular polarizer, and for two devices--a circulator and a nonreciprocal antenna element--based on the polarizer. The antenna element permits one antenna to be used both to transmit and to receive the reflected circularly polarized signals from a target.     

Millimetric Nonreciprocal Coupled-Slot Finline Components

Promising preliminary results are presented for isolators and a four-port circulator in novel finline structures in the frequency range 26.5-40.0 GHz. The basic configuration is a ferrite-loaded coupled-slot finline with the ferrite magnetized parallel with the direction of propagation. The nonreciprocal effects of the odd mode propagating alone and of the odd and even modes propagating are described. All structures exhibit a 20-dB isolation bandwidth greater than 3.6 GHz. It is suggested that such structures would also be suitable for higher frequencies.     

Passive Nonreciprocal HF Helicon Devices

Ferrite isolators and circulators are well known at microwave frequencies but are low-frequency limited and cannot be used in the HF region (below 100 MHz). A different approach to the basic nonreciprocal mechanism is reported here. This approach makes use of solid-state plasma waves, so-called helicon waves, that are nonreciprocal by their nature. Isolators using these helicon waves have been built in the 5-to 15-MHz range with great success and a helicon circulator has been demonstrated for the first time. This paper describes the mechanism by which these devices work and discusses their results. It is pointed out that in addition to helicon isolators and circulators, many other interesting and useful devices using helicon waves are possible.     

Nonreciprocal Coupling with Single-Crystal Ferrites

A calculation of nonreciprocal coupling in microwave circuits with small ferrite samples tuned to ferromagnetic resonance is presented. It is shown that this coupling may be applied to the construction of simple resonant isolators, gyrators and circulators. Experimental results for the coupling in rectangular and ridge guides, applying YIG spheres, are presented. The construction of a simple X-band waveguide junction, acting as a 4-port resonant circulator, is described. Such a filter circulator, which may act as a switch or a frequency selective power divider, can be made tunable over the waveguide frequency range, with a bandwidth in the order of 10 Mc, and with values of insertion loss and isolation, which are comparable to those of conventional circulators.     

A Microstrip Nonreciprocal Tunable YIG Filter

A nonreciprocal tunable YIG filter in a microstrip configuration has been constructed which makes use of a novel method of generating a circularly polarized field in the plane of a microstrip circuit. Nonreciprocities in excess of 40 dB have been obtained at X band with relatively low insertion loss and VSWR.     

Magnetooptic mode splitting in an anisotropic laser cavity

The normal modes of an anisotropic laser resonator containing an intracavity Faraday rotator have been investigated. Below a threshold value of rotation, the Faraday cell rotates the electric field vector of the linearly polarized modes. Above this value, each axial mode splits into two elliptically polarized waves. The frequency difference of these modes is then dependent on the Faraday rotation angle. Experimental results obtained using a 3.39-μ He-Ne laser with two Brewster windows and a YIG intracavity Faraday cell are in agreement with the results calculated from a normal mode analysis.     

Acoustic Surface Waveguides and Comparisons with Optical Waveguides

An overview is presented first of the various types of waveguides for acoustic surface waves which have been studied theoretically and experimentally. Many of these waveguides resemble certain waveguiding structures proposed recently for use in integrated and fiber optics. The similarities and differences between corresponding waveguiding structures in the two different fields are then discussed from the standpoints of their properties and their mechanisms of operation.     

Resonant Properties of Nonreciprocal Ring Circuits

The ring circuit investigated consists of a resonant ring guide coupled to a main guide. The properties can be described by the equations for the waves in the ring guide resulting from excitation in the main guide. The influence of nonreciprocity on the properties is investigated under conditions of varying coupling. The representation of the ring waves by the poles and zeros is chosen to permit interpretation of the results under the large variety of operational conditions with respect to coupling and nonreciprocity. The application for measuring the material constants of ferrites is discussed.     

Analysis of Nonreciprocal Coupled Image Lines

The effective dielectric constant method is used to analyze the nonreciprocal coupling properties of coupled image lines separated by a Iongitudinally magnetized ferrite slab. Two structures are considered, one incorporating low-dielectric-constant image lines (epsilon/sub r/ = 2.56), the other incorporating image lines consisting of high-dielectric-constant material (epsilon/sub r/ = 9.8). Results of dispersion characteristics, coupling parameters, and field distributions are presented.     

Nonreciprocal Reflection-Beam Isolators for Far-Infrared Use

Magnetoplasma reflection-beam isolators for submillimeter-wave use are discussed in theory and experiment. The basic device uses the Kerr transverse magnetooptic effect (plane of polarization of the EM wave in the plane of incidence, which is perpendicular to a dc magnetic field) in InSb near room temperature. When the semiconductor slab is covered with a thin dielectric layer acting as a matching transformer, improved performance is predicted and observed at 337 /spl mu/m, and very efficient isolator performance is predicted for 118 /spl mu/m. Physical arguments are presented to explain the nonreciprocal phenomenon and lead to better device design.     

An Investigation of Nonreciprocal Periodic Structures

The properties of a nonreciprocal ferrite-loaded rectangular waveguide, which is periodically loaded by thin metallic "inductive" diaphragms, are investigated experimentally. The propagation constants of the structure are measured and are compared with predictions based on measured values of the scattering parameters of a single diaphragm in the nonreciprocal waveguide. The agreement between theory and experiment is generally good except for the smaller spacings between the loading diaphragms. This discrepancy is attributed to the effects of higher order mode interaction.     

The Edge-Guided Mode Nonreciprocal Phase Shifter

Results of a theoretical study are presented for a four-region model of a nonreciprocal dielectric-ferrite loaded stripline phase shifter employing the edge-guided dynamic mode. The behavior of our model in terms of the differential phase shift, the insertion loss, and the effective bandwidth is explored as a function of the various parameters involved.     

Nonreciprocal HF signal transmission by surface helicon

Nonreciprocity of surface helicon propagation, its typical property which may be useful in practice, is stated experimentally. For this purpose the surface helicon has been separated from the bulk wave. The technique of the wave reflection from a groove of different depth cut on the semiconductor surface was used. Some other surface helicon characteristics are discussed as well.     

Nonreciprocal Two-Ports Represented by Modified Wheeler Networks

The extension of the (reciprocal) modified Wheeler network to include the more general nonreciprocal two-port is given. This representation is derived via a known decomposition of the general nonreciprocal network into two portions, one reciprocal, the other nonreciprocal. The reciprocal portion is then taken as the modified Wheeler network. Recombination of the elements results in the desired representation which is constituted of a minimum number, i.e., of eight, passive elements. Each of these is a natural idealization of a physical microwave component. Since six of the elements belong to the class of "bilaterally matched" networks, some of the properties of this class are discussed. Two of the bilaterally matched elements embody the nonreciprocal properties of the network: a one-way attenuator and a one-way phase-shifter. Many of the characteristics of the (reciprocal) modified Wheeler network carry over directly to this nonreciprocal representation. The microwave measurement of the network parameters is also indicated.