Nonreciprocal attenuation of magnetoelastic Rayleigh waves on bulk-YIG samples

Experimental results on nonreciprocal attenuation of magnetoelastic Rayleigh waves are reported for two bulk-YIG samples. In both cases, the nonreciprocity is found to be weak. In particular, the bulk-YIG version of the Lewis-Patterson YIG-film configuration (which exhibited a maximum nonreciprocity of about 20 dBs) is found to be essentially reciprocal.     

Double ridged waveguide phase shifters for broadband applications

The author presents an electromagnetic mode matching analysis of dual ridged waveguide phase shifters. The waveguide is loaded with a high dielectric material between the ridges, and the troughs are filled with ferrite toroids. The present structure offers nearly twice the bandwidth and less variation in nonreciprocity versus frequency as compared to the conventional dual toroidal phase shifter. An optimum design that maximizes nonreciprocity has been found. Effects of the dielectric constant and the trough dimensions are also presented. A differential phase shift of more than 100°/cm has been predicted for the new phase shifter     

Asymmetric fiber-optic coupler for LAN applications

This paper presents experimental results of an asymmetric, effectively nonreciprocal fiber-optic coupler fabricated from unequal core diameters multimode fibers. It is shown that the nonreciprocity is due to modal dependent coupling.     

Propagation characteristics of the magnetostatic surface wave inthe YBCO-YIG film-layered structure

Propagation characteristics of the magnetostatic surface wave (MSSW) in a YBa₂Cu₃O_7-x (YBCO)-yttrium iron garnet (YIG) multilayered structure are investigated. Effects of the superconductor on the MSSW are discussed with regard to the dispersion characteristics of both the phase and attenuation constants as a function of the air gap, between YIG and YBCO, taking into consideration the magnetic line-width of the YIG film. It was found that the nonreciprocity of MSSW is enhanced significantly by the superconductivity and depends on the magnetic line-width of the YIG film. To examine the effect of a YBCO on the MSSW propagation, experiments are carried out using a commercially available YIG film. Magnetic losses at low temperature are briefly discussed with experimentally observed nonreciprocity     

Multilayered open dielectric waveguide with a gyrotropic layer

Open dielectric waveguides with a gyrotropic layer have been studied with a view to find structures in which the nonreciprocity in the propagation constant is maximized. A prediction based on a qualitative analysis and numerical studies for confirming the theory are included.     

基于布里渊散射的保偏光纤环应力分布特性研究

保偏光纤环是光纤陀螺的核心部件,其性能受温度的影响较大,主要表现为热致互易相移,影响光纤陀螺的精度。针对该问题,提出采用应力分布法测量光纤环的温度非互易相移。通过对不同温度点的光纤环应力分布数据进行分析,建立光程对中数学模型,基于该模型对光纤环的尾纤进行适当调整,改进其光学对称性,降低由温度变化引起的非互易相移。通过陀螺整机实验表明:该方法能大幅提高光纤陀螺的精度,过程简单方便,对成品光纤环具有一定的修复作用,提高了成品率,实用性较好。     

Optical isolation in silicon waveguides based on nonreciprocal Raman amplification

The longitudinal mode-field components in strongly confining crystalline-silicon waveguides cause a forward-backward asymmetry of the stimulated Raman effect. This nonreciprocity can be used to realise isolators with dynamically reconfigurable isolation direction.     

Vibration immunity for optical-fiber current measurement

Optical-fiber measurement of electric current can be rendered immune from the effects of environmental vibration by utilizing the nonreciprocity of the Faraday effect in an arrangement which propagates light simultaneously in the two directions around a fiber loop enclosing an electric current. The system is compared with a back-reflection arrangement. Temperature variations are also suppressed     

Digital Nonlinear Metasurface with Customizable Nonreciprocity

Recently, investigation of metasurface has been extended to nonreciprocity through breaking time‐reversal symmetry. Among a number of magnetless strategies, nonlinearity is an important nonreciprocal principle amenable to the metasurface. As passive analog‐based devices, most of the existing nonlinear nonreciprocal metasurfaces are inherently characterized by the relatively unchangeable performance, sharp frequency response, and hysteresis loops. Here, an analog–digital–analog mechanism is proposed to realize the nonlinear nonreciprocity, which provides a digitally reconfigurable solution for a family of nonreciprocal performance within a shared hardware architecture. This concept is validated by a metasurface prototype with the integration of a digital module at microwave frequencies. Based on the proposed mechanism, the properties can be customized as demanded, ranging from a normal reciprocal response to a variety of nonreciprocal functions, including electromagnetic (EM) diode and EM unidirectional limiting functions, which have been experimentally demonstrated with direction reversibility and threshold tunability. The proposed metasurface is also underpinned by the nonhysteretic performance and wide operating bandwidth, thereby potentially making it an inexpensive and stable candidate for advanced manipulations of EM waves.     

A new heterodyne fiber-optic gyroscope using electrooptic frequency shifter

In this paper, a novel heterodyne detection technique of rotation rate is described. This technique uses highly birefringent single-mode fiber and an electrooptic frequency shifter for a heterodyne interferometric system, and thus releases the use of acoustooptic devices and also the nonreciprocity which usually exists in a heterodyne fiberoptic gyroscope. Initial experimental results show a good linearity of the scale factor.     

Analysis of a coupled slotline on a double-layered substratecontaining a magnetized ferrite

Nonreciprocity in the propagation characteristics of the even and odd modes in magnetized-ferrite-loaded double-layered coupled slotlines is studied. The analysis is based on Galerkin's method applied in the Fourier transform domain. Numerical results are presented for various values of structural parameters. As a result, it is found that the waveguide structures studied have sufficient nonreciprocity in propagation constants for isolators and four port circulators     

A novel finite-element method for nonreciprocal magneto-photonic crystal waveguides

A new formulation of the finite-element method to analyze nonreciprocal waveguides in magneto-photonic crystals (MPCs) is proposed. Accurate solutions of light propagations for two different directions are obtained by the asymmetrical input condition. As numerical examples, the performance of a waveguide-type optical isolator in MPCs designed by the eigenmode analyses is confirmed by using this method. Subsequently, an effective way to enhance the nonreciprocity of the optical isolator is shown.     

Nonreciprocity in optical waveguide: experiment

We have demonstrated nonreciprocity in a magneto-optic waveguide by measuring the polarisation of the light emerging out of the channel waveguide, where a magnetic field was applied along the propagation direction. Nonreciprocity in an optical waveguide, in which the phase matching between the orthogonally polarised modes is not satisfied, leads to the opposite rotation of the major axis of the ellipse of the output light polarisation as reversing the propagation direction.     

Nonreciprocal Properties of Vacuum-Deposited InSb Films at 87 GHz (Short Papers)

Room-temperature measurernetits were taken at 87 GHz on isolators fabricated by using thin vacuum-deposited hot-wire-recrystallized InSb films in both the Faraday-rotation mode and the field-displacement mode. In the Faraday-rotation mode, an insertion loss of 9 dB, a nonreciprocity of 10 dB, and an isolation of 19 dB were obtained in an external magnetic field of 8 kOe.     

Electromagnetic study of a ferrite coplanar isolator suitable for integration

The transmission coefficient of a nonreciprocal coplanar waveguide (CPW) using ferrite rods is studied. A new approximate method is proposed to evaluate the propagation constant of such a perturbed waveguide, which is based on the use of numerical data referring to the nonperturbed waveguide. We have estimated the value of the nonreciprocity effect and settled the condition of the validity of our theory. Some experimental data of a CPW with ferrite inclusions are also presented.     

Magnetically programmable bistable laser diode with ferromagneticlayer

A new design of bistable laser diode, which consists of a gain section, absorption section, and nonreciprocal section, is proposed. The nonreciprocal section is made of a semiconductor optical amplifier covered by a ferromagnetic layer. The nonreciprocity of magneto-optical effect significantly modifies a photon density distribution in the laser cavity and enlarges a width of hysteresis loop of bistable laser diode. The bistability can be switched on or off by reversing magnetization of the ferromagnetic layer     

Surface waves guided by a plate made from a bianisotropic resonance metamaterial

The dispersion characteristics, the distribution of energy fluxes, and the polarization of the magnetic field of surface waves formed in free space by a bianisotropic-material layer with resonance and anisotropic chirality, permittivity, and permeability are studied theoretically. The transmission and reflection spectra for lattices of resonance planar elements exhibiting magnetoelectric interaction are investigated experimentally. The nonreciprocity of microwave transmission in structures consisting of a lattice and a transversely magnetized ferrite plate is also investigated experimentally. The qualitative agreement of experimental results and theoretical predictions is established.     

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.     

Complex media microstrip ridge structures: formulation and basiccharacteristics of ferrite structures

Microstrip transmission lines residing on bianisotropic material ridges embedded in a multilayered environment are studied using a coupled set of integral equations (IE's). The full-wave IE formulation accounts for general linear media in the ridge region using equivalent polarization currents residing in a multilayered bianisotropic background. Numerical results showing basic propagation characteristics are presented for a variety of single and coupled ferrite ridge structures. It is shown that the use of finite width ferrite ridges as either substrates or superstrates can produce nonreciprocity while confining the ferrite material to a small area in the vicinity of the transmission line     

法拉第手征圆波导中旋磁性和手征性的复合效应

基于分离变量和Mller求根法,本文详细地分析了均匀和非均匀法拉第手征圆波导中混合模的传输特性;揭示了模分裂、对称和非互易性、后向波和衰减随不同本构参数的变化規律,而这不同于一般旋磁和互易手征波导情形。