Nonreciprocal Properties Research Articles

Temperature-stabilized one-way electromagnetic modes in a magneto-optic unidirectional waveguide

We investigate the temperature effect of the unidirectional (one-way) electromagnetic mode in a symmetrical gyromagnetic photonic crystal (PhC) waveguide. The results show that the nonreciprocal properties of the one-way edge mode are insensitive to the temperature variation of the waveguide from 233 to 333 K. Such a temperature-stabilized nonreciprocal PhC waveguide may have potential applications in future electromagnetic engineering.

Long-range surface magnetoplasmon on thin plasmon films in the Voigt configuration

This study elucidates the characteristics of a long-range surface magnetoplasmon (LRSMP) that propagates on a plasmon film with the Voigt configuration. Particle-in-cell (PIC) simulations and theoretical analyses are performed. Simulation results indicate that LRSMP has non-symmetrical fields. The proposed scheme also verifies the non-reciprocal properties of LRSMP as the direction of an applied external magnetic field is reversed. When surface waves propagate on a plasmon film across an interface on one side of which long-range surface plasmon (LRSP) is allowed while on the other side of which LRSMP is allowed, the interface behaves similar to a defect and transforms the surface waves into radiation modes owing to the mismatch between the field patterns of LRSP and LRSMP. Furthermore, PIC simulation results confirm the presence of a new high-frequency LRSMP whose frequency exceeds the plasma frequency and lacks a LRSP counterpart.

Nonreciprocal amplitude-frequency resonant response of metasandwiches “ferrite plate-grating of resonant elements”

New microwave nonreciprocal properties are investigated in “ferrite plate – grating of resonant elements” metasandwiches arranged along the axis of a rectangular waveguide in a transverse constant magnetic field. Giant nonreciprocity in the transmission is observed at the ferromagnetic resonance frequencies at certain values of the magnetic field under conditions of a mutual influence between the ferromagnetic and the grating resonances. In addition, nonreciprocal splitting of the resonance in grating elements is observed under small magnetic field, which is much less than the field necessary to the ferromagnetic resonance excitation. The nonreciprocal transmission does not take place in the case of free ferrite in the absence of a grating. Sign reversal of the nonreciprocity is observed, when ferrite transfers to the opposite side of a grating as well as under certain values of the constant magnetic field, when the sign reversal of difference between frequencies of the ferromagnetic resonance and the grating resonance takes place. Nonreciprocal effects are explained by the interaction between precessing spins in ferrite and a magnetic field of the surface wave, formed by a grating, and by coupling between the resonances of grating elements. It has been shown theoretically that microwaves in waveguide with bianisotropic layer, simulating a grating of resonant elements, are elliptically or circularly polarized with frequency and spatially – dependent rotating sense of the microwave magnetic field. The nonreciprocal effects have been observed for different grating elements: for both electric dipoles and chiral elements.

Design of three new types of active quasi‐circulator modules

AbstractAnalysis and design of three novel active quasi‐circulator modules are presented, which use the nonreciprocal properties of microwave unilateral power divider/combiner and amplifiers.These modules have many variations and can be used for very wide frequency range depending on the type of the unilateral amplifier used. Also, they can be used in MMICs as active circulators and also in other high‐frequency applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 689–694, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24998

A “couplonic” approach to multilayer magneto‐photonic crystals

AbstractIn the frame of an exact (non‐perturbative) formulation of the coupled‐mode theory, we describe the non‐reciprocal properties of a one‐dimensional multilayer magneto‐photonic crystal with alternate dielectric and magneto‐optical materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

General finite-element modeling of 2-D magnetophotonic crystal waveguides

A new finite-element method for characterizing magnetophotonic crystal (MPC) waveguides with polarization conversion properties is proposed. To treat arbitrarily anisotropic magnetophotonic materials, a vector Helmholtz equation in terms of three components of electric or magnetic fields is discretized with the so-called edge/nodal hybrid elements. Nonreciprocal lightwave propagation properties are obtained by using an asymmetrical input condition. This method is validated by simulation of an optical isolator based on an MPC waveguide with a compensation wall exhibiting inclined magnetization.

Phase shift in GaAs magnetoplasma ridged parallel-plate waveguides

The nonreciprocal properties of lossy GaAs magnetoplasma ridged parallel-plate waveguides are assessed at 250 GHz using a gyroelectric performance factor. The optimum phase shift for a two-layer structure is predicted when the magnetoplasma semiconductor is in a superstrate position with a low-permittivity dielectric substrate below a half-height ridge. This arrangement exhibits TEM to TM01 mode conversion. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 419–422, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21003

Nonreciprocal electromagnetic properties of nanocomposites at microwave frequencies

We report on the effects of composition and external magnetic field on the microwave permeability tensor of $\mathrm{Ni}∕\ensuremath{\gamma}{\text{\ensuremath{-}}\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ nanocomposites. When compared to the zero-field case, the field measurements of the permeability tensor $\overline{\ensuremath{\mu}}$ exhibit nonzero off-diagonal components giving evidence of the nonreciprocity of wave propagation in these nanostructures. We observe that the diagonal and off-diagonal elements of $\stackrel{}{\ensuremath{\mu}}$ of these nanocomposites depend sensitively on their Ni content and of the applied static magnetic field. These experimental results are analyzed within a recently developed multiscale modeling [S. Mallegol et al., Phys. Rev. B 68, 174422 (2003)] and can be understood as arising from magnetostatic intergranular interactions via a mean-field approximation. The application of these heterogeneous nanomaterials open possibilities for the design of field-controlled nonreciprocal components used in microwave integrated circuit technology.

Algorithms for Estimating the Complete Group of Polarization Invariants of the Scattering Matrix (SM) Based on Measuring All SM Elements

The procedure for estimating polarization invariants of the backscattering matrix in horizontal-vertical basis is considered for radar observation of arbitrary nonreciprocal objects. Two polarization invariants are added to the well-known six Huynen-Euler invariants. These new invariants (nonreciprocity angle and difference in absolute phases of the symmetric and antisymmetric parts of the scattering matrix) describe the nonreciprocal properties of the object itself. With the simultaneous measurement of all eight quadratures of the scattering matrix elements, the closed-form expressions for calculating the eight polarization invariants are given. The derived expressions are the starting point for complete estimation of the polarization properties of arbitrary radar objects with a nonsymmetric scattering matrix. The given approach can be used to study various polarization effects in remote radar sensing of artificial and natural objects, and also to simulate polarization measurement processes and estimation errors caused by the measurements of scattering matrix elements at different instants.

Ferrite Properties and Technology Issues for Improved Microwave Systems

ABSTRACTMicrowave device engineers continually seek materials advances to improve performance of magnetic components at reduced size and cost. Wherever possible, microstrip or stripline device configurations are adopted in preference to bulky waveguide structures. In radar and communications applications, the nonreciprocal propagation properties of ferrites are essential for realizing phase shifters, circulators, isolators, and power limiters. The introduction of superconductor circuits has led to the development of very low-loss phase shifters and circulators. Recent demonstrations of tuning reciprocal rf permeability by varying the state of magnetization at very low magnetic fields has led to the development of high-speed, high-Q tunable filters. In this paper, design issues of four classes of microwave device are reviewed from the standpoint of their ferrite material requirements: (1) low-loss microstrip phase shifters (2) microstrip tunable resonators, (3) self-biased microstrip circulators with normal or in-plane uniaxial anisotropy, and (4) high-power quasi-optical circulators.

Modeling of Magnetooptical Waveguides via Transfer Matrix Technique and Wide-Angle Finite Difference Beam Propagation Method

Two extended numerical formulations are simultaneously applied to the investigation of TM mode propagation in magnetooptical waveguides: (1) the transfer matrix technique, applied to the modal propagation constant calculation in multilayer waveguides, and (2) the wide-angle finite difference beam propagation method, applied to the nonparaxial beam propagation simulation in longitudinal varying waveguides. The second utilizes the Crank-Nicholson scheme and Padé approximants for the discretization of the wave equation. The usefulness of these two numerical formulations is tested for the nonreciprocal properties of TM mode propagation in a magnetooptical directional coupler.

A generalized Ginzburg-Landau approach to second harmonic generation

We develop a generalized Ginzburg-Landau theory for second harmonic generation (SHG) in magnets by expanding the free energy in terms of the order parameter in the magnetic phase and the susceptibility tensor in the corresponding high-temperature phase. The non-zero components of the SHG susceptibility in the ordered phase are derived from the symmetries of the susceptibility tensor in the high-temperature phase and the symmetry of the order parameter. In this derivation, the dependence of the SHG susceptibility on the order parameter follows naturally, and therefore its nonreciprocal optical properties. We examine this phenomenology for the magnetoelectric compound Cr$_2$O$_3$ as well as for the ferroelectromagnet YMnO$_3$.

The use of FDTD for the analysis of magnetoplasma channel waveguides

The finite-difference time-domain (FDTD) method is used for the analysis of magnetoplasma rectangular channel waveguides. Single and parallel-coupled waveguides are considered. The effect of varying the amplitude and the orientation of the bias magnetic field B/sub 0/ on the dispersion characteristics of the first modes is examined. However, the FDTD formulation, does not excite evanescent modes for a sufficiently long time interval, particularly when in the presence of the propagating or dynamic modes. As a result, the nonreciprocal properties of these structures, primarily associated with the evanescent modes, could not be investigated.

Non-reciprocal effects of complex-coupled distributed-feedback structures resulting from the phase difference between the coupling constants

We investigate theoretically the non-reciprocal properties of a complex-coupled periodical structure resulting from the phase difference between the index- and gain-coupling constants. We show that this effect can give rise to a spectacular non-reciprocity of the reflectivity spectrum. If the two contributions are out of phase by ± π 2 , they act together in one direction, but they cancel out each other by destructive interference in the other direction. We also investigate the non-reciprocal emission of a complex-coupled distributed-feedback laser at threshold. We believe that such properties could be useful in designing one-way-only filters in communication or data processing systems.

Asymmetric multimode Y-junction splitters

The wavelength-independent, non-reciprocal splitting properties of the asymmetric, multimode Y-junction make it an ideal device for use as a low-loss, low-power tap in a concatenated linear bus. The properties of a two-dimensional slab model of the junction are investigated and the results of ray-tracing, modal and numerical beam propagation method (BPM) techniques are compared. Minimization of splicing loss between the ports of a square-core, three-dimensional buried channel waveguide version of the device and a multimode fibre is also addressed.

Resonance mode expansions and exact solutions for nonuniform gratings.

Resonance modes play an important part in understanding linear nonuniform gratings, analogous to the role played by waveguide modes in waveguide theory. Using resonance mode expansions, exact expressions are obtained for the fields, the grating profile, and the reflection and transmission spectra for a large class of nonuniform linear gratings. The method can deal with linear gratings that couple a pair of either copropagating or contrapropagating modes. The formalism covers the effects of gain and loss (in the small signal limit), chirp, taper, and birefringence. The exact solutions can be used to investigate designs for grating structures. Two detailed example applications of the technique are presented here: an exact solution for a grating that supports only a single resonance mode, and an exact solution for a grating that has nonreciprocal reflective properties from its two ends. \textcopyright{} 1996 The American Physical Society.

Parallel pump spin wave instability threshold in thin ferromagnetic films

A rigorous theory of parallel pump instability threshold of spin waves in ferromagnetic films is developed. Dipole and exchange interactions, the dipole-dipole hybridization of spin wave branches, and the magnetocrystalline and induced anisotropies are taken into account. Expressions for the parallel pump instability threshold are obtained in general form which can be used to calculate the threshold of a single ferromagnetic layer or a multilayered structure containing an arbitrary number of ferromagnetic films. The influences of the dipole-dipole hybridization of parametrically generated spin waves and of their nonreciprocal propagation properties on the threshold are discussed.

Theory of magnetostatic waves for in-plane magnetized isotropic films

A modified formulation of the Damon-Eshbach theory of magnetostatic waves for in-plane magnetized isotropic film is presented. Mode dispersion curves and magnetization profiles are examined in detail. Several new results are obtained: (i) Volume mode critical angle effect. (ii) Nonreciprocal volume mode properties. (iii) Volume mode profiles which show quasi-pinning at the film surfaces, even though there are no explicit boundary conditions on the surface spins in the theory. (iv) Physical explanation of the out-of-band surface mode frequencies in terms of the dipole fields for circularly polarized modes. (v) Demonstration of the continuous nature of the change from volume mode to surface mode character for the near-uniform mode at low wave number due to competing dipole field effects.

Adiabatic polymer-glass-waveguide all-optical switch

We propose an adiabatic all-optical switch that is composed of an asymmetric Y-branch ion-exchanged glass waveguide with a strip of nonlinear polymer loaded on top of one branch. The properties of nonlinear wave propagation in the device are investigated in detail. By extending the effective-index method to the analysis of nonlinear waveguides, we calculate the nonlinear dispersion curves in successive sections to explain the evolution of normal modes in the device. As the multivalued propagation constants exist in the tapered directional coupler region, the device possesses an abrupt switching behavior and nonreciprocal properties. To demonstrate nonlinear switching behaviors in the Y-branch waveguide further, we employ a beam propagation method to simulate optical-field propagation. The inputs by three different ports are investigated, and the results agree well with the dispersion-curve analysis.

Nonreciprocal Phenomena in Coupled Guides Filled with Chiroferrite Media

A new class of waveguides, chiroferrite filled coupled guides, (CFCL) is introduced which exhibit some novel nonreciprocal properties owing to the interaction effects between gyrotropy and chirality. These CFCL structures consist of two parallel guides coupled via a chiroferrite or ferrite-chiral composite medium. The phenomena occurring in CFCL in the presence of two propagating even and odd modes are analysed using the coupled mode method. Two nonreciprocal phenomena are observed. It is found that the polarization plane of the electromagnetic wave propagating in the structure rotates with different rotation angle and its polarization ellipticity having different values when the magnetization or propagation direction is reversed. These nonreciprocal behaviours show the feasibility of CFCL structures as a new type of nonreciprocal devices for millimeter and optical wave applications. The results of the analysis are applied to derive the scattering matrix of a section of symmetrical CFCL. The conditions in...