Waveguide and resonator perturbation techniques measuring chiralityand nonreciprocity parameters of biisotropic materials

Waveguide and resonator perturbation techniques are considered for determining electromagnetic parameters of general biisotropic, or nonreciprocal chiral, materials. The bisotropic materials are the most general linear isotropic media, whose constitutive relations are governed by four complex material parameters. The material parameters of bisotropic media can be obtained through measuring the change in the propagation constant of waveguide modes or measuring the shift in the resonant frequency for resonators with perturbation techniques. To measure these parameters a method utilizing waveguides or cavity resonators with two degenerate modes is proposed     

Isotropic Maxwell-Garnett model for biisotropic-in-biisotropic mixtures

The Rayleigh scattering response of an electrically small biisotropic sphere immersed in an ambient biisotropic medium has been utilized in constructing a Maxwell-Garnett model of a composite material formed by randomly dispersing biisotropic spheres in a biisotropic host medium. It is anticipated that this work will be of interest for estimating the electromagnetic properties of particulate media.     

Transverse coupling between two general biisotropic slabs

The general formulation for the determining of transverse coupling behaviour between two different biisotropic slabs is proposed based on the method of conventional field perturbation, and some special cases are considered. Since biisotropic medium is a generalization of the well-studied nonreciprocal and reciprocal chiral media, our results are suitable for much more cases.     

New approach for equalising phase velocities in coupled microstriplines

A new method for correcting the difference between the phase velocities of even and odd modes in coupled microstrip lines is suggested. The method is based on use of a biisotropic substrate with an appropriate value of the parameter ξ²/εμ     

Reciprocity and the concept of the brewster wavenumber

Reflection of planewaves at the planar interface of two biisotropic media has been examined in order to obtain the Brewster wavenumber. This examination shows that the Brewster wavenumber is, at least, not necessarily affected by the reciprocity or the non-reciprocity of the media on either side of the planarinterface.     

Wave Propagation in Inhomogenous Slab Waveguides Embedded in Homogeneous Media

Wave propagation in inhomogeneous slab waveguides embedded in homogeneous media is analyzed by rising the uniform asymptotic technique. This technique accurately evaluates the effect of the refractive-index profiles with various core and cladding structures on the guided modes. We calculate the guided modes of waveguides with asymmetric claddings in the eases of a near-parabolic profile core and a quasi-Gaussian profile core. The results show that the third-order asymptotic solution is accurate for all the guided modes in the case of the near-parabolic profile core and for modes far from cutoff in the quasi-Gaussian core case. The dispersion relation indicates that modes guided in strongly asymmetric profiles have almost the same propagation constants as odd-order modes of propagation in the symmetric structure.     

An investigative report on the constructive relations of linear magnetoelectric media

Conventional treatment of linear magnetoelectric media assumes their constitutive relations to have certain symmetries. This assumption is based on static analysis, but is mostly used for alternating fields. Experimental evidence in support of the assumption is certainly incomplete and inadequate, and may be incorrect. The assumption negates the existence of reciprocal biisotropic media, which nevertheless exist in abundance. These and other inadequacies are critically analyzed.     

Scattering by a Biisotropic Body

The problem of two-dimensional scattering by a four-parameter homogeneous biisotropic body is handled via a new contour integral technique where only tangential fields at interfaces are involved (and numerically modeled). This original work has resulted in the development and validation of a scattering code BIS2D2/BIG2D to calculate the depolarization/radar cross section (RCS) of a biisotropic structure at normal incidence     

Theory of nonreciprocal and nonsymmetric uniform transmission lines

A nonreciprocal and nonsymmetric transmission line is one which has different line parameters for waves propagating in opposite directions. Such a concept emerges in problems of electromagnetic wave propagation in layered structures of biisotropic (nonreciprocal chiral) media. It is shown that the well-known transmission-line formulas can be generalized for the present transmission line     

Radiation patterns of electric dipole antenna in the presence of a biisotropic sphere

Analytic expressions of the dyadic Green's function of an arbitrary electric current source embedded in a general biisotropic sphere are presented at first, and the radiation characteristics of an electric dipole antenna placed on the surface of a biisotropic sphere lens are examined. The effects of the electric-and the magnetic-coefficients (ξ _e and ξ _m ) of biisotropic medium on the radiation patterns of electric dipole antenna are investigated in detail.     

Spectral dyadic Green's function formulation for uniaxial bianisotropic superstrate-substrate structure

In this paper, spectral-domain dyadic Green's functions for the time harmonic electric current source embedded in a two-layer grounded uniaxial bianisotropic media are obtained using Fourier tranform. It is shown that in the uniaxial bianisotropic medium, total spectral electromagnetic field can also be separated into the superposition of transverse electric (TE) and transverse magnetic (TM) wave. Because of the generality of constitutive relations our results include the special cases of achiral, uniaxial, reciprocal and nonreciprocal biisotropic media.

     

On the scattering of an obliquely incident plane wave by a biisotropic cylinder

Scattering of an obliquely incident electromagnetic plane wave by an infinitely long, homogeneous, biisotropic cylinder is addressed. The ambient host medium considered is isotropic, homogeneous and dielectric-magnetic. It is observed that the constitutive coupling of the electric and the magnetic fields in the biisotropic material causes the cross-polarization component of the scattered field not to vanish even for the normal incidence case.     

Hybrid mode phase matching and effective nonlinear coefficient forsecond harmonic generation in biaxial waveguides

Phase matching between fundamental and second harmonic hybrid guided modes in nonlinear biaxial planar waveguides is determined for the first time based on principal axes orientations of the film, substrate, and cover. We have derived an expression for the effective nonlinear coefficient D_eff of hybrid modes in a biaxial waveguide and have calculated this coefficient numerically along the effective index phase match loci for these modes supported by a POM waveguide surrounded by isotropic media. The optimum phase matching orientations are determined for a fixed waveguide thickness. Dispersion of the principal indexes is considered     

手征光纤中导模的色散特性

从手征介质中的电磁场本构关系出发，利用麦克斯韦方程组，对纤芯和包层都是手征介质构成的阶跃型手征光纤进行了解析求解，导出了模式场解和特征方程。用数值方法研究了纤芯和包层的手征导纳对手征光纤中导模的归一化传播常数、群延迟、波导色散等特性的影响。     

Exact analytic solutions to the nonlinear wave equation for asaturable Kerr-like medium: modes of nonlinear optical waveguides andcouplers

Exact analytic solutions to the nonlinear wave equation for a lossless saturable Kerr-like medium are found. The nonlinearity is an intensity-dependent refractive index which saturates according to the model n²=n₀²±a|E|²/(1+b|E| ²). The solutions to the wave equation are used to determine the TE power-dependent dispersion relations, and therefore the guided modes, of a single waveguide structure and of a directional coupler whose coupling medium is the nonlinear saturable material. Although the interaction between the sinh- and cosh-like modes of the coupler, and therefore the coupling length, is not treated in this work, it is shown that the critical power, defined in the literature to be the level of input power above which 100% of the power cannot be switched between the guides of a coupler, is a mathematical misinterpretation in both saturable media as well as in nonsaturable Kerr media. The absence of a critical power in single waveguide structures is also demonstrated. Parameters of GaAs-based waveguides and of a GaAs-GaAlAs MQW coupling medium are used in the numerical analysis     

Simplified analysis of a polarizing optical fiber

A simplified analysis of anisotropic, polarizing fibers consisting of a circular core placed in a highly elliptical inner cladding is presented. The simplification consists of treating the problem in the scalar approximation and of letting the highly elliptical inner cladding degenerate into two semi-infinite half spaces bounded by plane surfaces. The birefringence of the fiber material is not explicitly included in the analysis. Instead, it is assumed that modes that are linearly polarized at right angles to each other `see' effectively different isotropic media. The solution yields the field distributions and dispersion curves for guided modes right to their points of cutoff. Leakage losses of modes below cutoff are estimated with low accuracy. The results are useful for designing polarization maintaining fibers or fiber polarizers     

异向回旋媒质平板波导的模式特性分析

研究了异向回旋媒质平板波导中电磁波的模式特性,给出了电磁波在异向回旋媒质中的导行条件。根据媒质介电常数张量分量取不同的符号,分4类情况分析不同媒质参数条件下传播模式的特性,并讨论了不同情况下虚横波数模式的存在性。结果表明这种媒质中的电磁波模式与一般媒质有很大不同。     

Guided Waves in Moving Media

This paper contains a theoretical study of the guided waves in a moving isotropic medium. The normal modes which can exist in a circular or rectangular wave guides are found by solving the Maxwell-Minkowski Equations subject to the appropriate boundary conditions. By certain transformations of field vectors, it is possible to change the Maxwell-Minkowski Equations into familiar forms such that the method of vector potentials can be applied to derive complete expressions for the field vectors. The results demonstrate that expressions for the propagation constant and the transverse-wave impedance and admittance in stationary media are modified by terms independent of the guide geometry when the media are moving.     

Pseudoreversibility condition for minimizing radiation loss at discontinuities of coupled waveguides

A design condition is derived for lossless discontinuities of coupled waveguides by finding solutions, which satisfy time reversibility of guided modes. The derived condition is used as a bound for minimizing radiation loss. Even when there is strong coupling between guided modes, the radiation loss can be minimal. A comparison between different grating designs in a 2 /spl times/ 2 backward coupler demonstrates that two coherently coupled gratings can significantly reduce radiation loss, as compared to a single grating.